Organic Chemistry Solutions for ICSE Class 10 - Selina Publishers PDF

Selina Concise Solutions for Class X Chemistry Chapter 12 – Organic chemistry Intext Questions 1. (a) What are organic compounds? Ans: Any chemical substance with carbon-hydrogen bonds is considered an organic compound. Organic chemis...

Selina Concise Solutions for Class X Chemistry Chapter 12 – Organic chemistry Intext Questions 1. (a) What are organic compounds? Ans: Any chemical substance with carbon-hydrogen bonds is considered an organic compound. Organic chemistry is the science that studies the characteristics, reactions, and syntheses of organic substances. (b) What is vital force theory? Why was it discarded? Ans: The Vital Force Theory was proposed by Berzelius in 1809, and it states that organic chemicals can only be created in live cells and that preparing them in laboratories is impossible. Friedrich Wohler demonstrated that an organic chemical (urea) could be produced in the laboratory, thus it was discarded. 2. (a) Name a few sources of organic compounds. Ans: Plants, animals, coal, petroleum, and wood are all sources of organic molecules. (b) Give the various applications of organic chemistry. Ans: Organic chemistry is utilised in the manufacturing of soaps, shampoos, powders, and perfumes, among other things. Organic chemicals are also found in other fuels such as natural gas and petroleum. Organic compounds are also used in the fabrics that we employ to produce diverse garments. Class X Chemistry www.vedantu.com 1 3. Organic chemistry plays a key role in all walks of life. Discuss Ans: Organic compounds can be found in almost any environment. They can be found in: 1. It's used to make soaps, shampoos, powders, and perfumes, among other things. 2. It is found in foods such as carbs, proteins, lipids, and vitamins. 3. Drugs, explosives, dyes, and insecticides are all prohibited. 4. Petroleum and natural gas are both organic substances. As a result, organic substances are important in many aspects of existence. 4. Carbon shows some unique properties, name them. Ans: Carbon has the following distinctive properties: 1) Tetravalency of carbon 2) Catenation. 3) Isomerism. 5. Explain the following: (a) Tetravalency Ans: To achieve octet, carbon cannot lose or receive electrons. As a result, it has four electrons in common with other atoms. Tetravalency of carbon refers to the property of carbon that allows it to make four covalent connections. (b) Catenation Class X Chemistry www.vedantu.com 2 Ans: The bonding of atoms of the same element into a chain is known as catenation. An open-chain compound is one in which the ends of a chain or ring are not linked to each other, whereas a closed-chain compound is one in which the ends are bonded in a ring (a cyclic compound). 6. Write any four properties of organic compounds that distinguish them from inorganic compounds. Ans: Organic substances have four characteristics that set them apart from inorganic compounds: Carbon is present. They are soluble in organic solvents. Covalent bonds are formed. The melting and boiling points are both low. 7. Why are organic compounds studied as a separate branch of chemistry? Ans: Because of the particular nature of the carbon atom, a huge number of compounds can be formed. As a result, a new field of chemistry is required. 8. What are hydrocarbons? Compare saturated and unsaturated hydrocarbons? Ans: Saturated hydrocarbons have only single carbon-carbon bonds. Unsaturated hydrocarbons have double or triple carbon-carbon bonds (more hydrogens can be added). Class X Chemistry www.vedantu.com 3 9. Give reason for the existence of the large number of organic compounds. Ans: Catenation, or the formation of covalent bonds with other carbon atoms, is a simple process that allows carbon to create longer chains and greater mass structures. This is the cause for the large amount of carbon-based organic molecules found in nature. 10. Give at least one example in each case to show the structure of isomers of: (a) Single bond compound Ans: n-Pentane (b) Double bond compound Ans: Ethene (c) Triple bond compound Ans: Ethyne 11. Name a compound of each type and draw the figure, (a) Saturated hydrocarbons Ans: n-Pentane (b) Unsaturated hydrocarbons Ans: Ethyne 12. Define substitution and addition reactions. Give an example for each. Ans: Addition reactions are the reaction, in which reagent is added by breaking the unsaturated bonds (double or triple bond) e.g: By adding hydrogen in the presence Class X Chemistry www.vedantu.com 4 of a catalyst, unsaturated hydrocarbons can be converted to saturated hydrocarbons. Substitution reactions are reactions in which a reagent substitutes one atom or a group of atoms from the reactants. e. g. In the presence of sunlight, CH4+Cl2 will produce CH3Cl+HCl. Intext Questions 1. Define a functional group and give the structural formula of the following functional groups: Ans: Functional group is a group of atoms that are responsible for the characteristic reactions of a particular compound. (a) Ketone Ans: (b) Alcohols Ans: R-OH (c) Aldehydes Ans: R-CH=O 2. Write the name and formula of fourth member of the following homologous series: Class X Chemistry www.vedantu.com 5 (a) Alkyne Ans: Butyne C4H6 (b) Alcohol Ans: Butanol C4H9OH 3. Which part of an organic compound determines (i) Physical properties Ans: Alkyl part (ii) Chemical properties Ans: Functional group 4. Name the alkyl radical and the functional group of the following organic compounds: (a) CH3OH Ans: Alkyl radical- Methyl (CH3.) Functional group- alcohol (OH) (b) C2H5OH Ans: Alkyl radical- Ethyl (C2H5.) Functional group- alcohol (OH) (c) C3H76CHO Ans: Alkyl radical- Propyl Class X Chemistry www.vedantu.com 6 Functional group- Aldehyde (d) C4H9COOH Ans: Alkyl radical- Butyl Functional group- carboxyl (e) CH3COOH Ans: Alkyl radical- CH3. Functional group- Carboxyl (f) HCHO Ans: Alkyl radical- H. Functional group- Aldehyde 5. (a) What is an alkyl group? Ans: A group of atoms formed by the loss of a hydrogen atom from an alkane is called alkyl group. (b) Give the names of any three alkyl radicals. How are they formed? Ans: Three alkyl radicals are: Methyl, ethyl, Propyl. These are formed by losing one hydrogen atom. CH4→CH3. + H. C2H6→C2H5. + H. C3H8→C3H7. + H. Class X Chemistry www.vedantu.com 7 6. Give the names and the structural formula of the first three members of the homologous series of alkanes. Ans: Methane (CH4), ethane(C2H6), and propane (C3H8) are the first three members of the homologous series of alkanes. 7. (a) What is a homologous series? Ans: A homologous series is a collection of organic compounds with identical structures and chemical characteristics that differ only by the presence of a CH2 group. (b) What is the difference in the molecular formula of any two adjacent homologues: (i) In terms of molecular mass. Ans: The molecular formula difference between any two neighbouring homologues is 14 a.m.u. (ii) In terms of number and kind of atoms per molecule? Ans: It is three atoms apart. It differs by one carbon atom and two hydrogen atoms. So, two kinds of atoms. Exercise- 12 A 1. Write the IUPAC name of the following: (a) Class X Chemistry www.vedantu.com 8 Ans: 2,2-Dimethylpropane (b) Ans: 2-Methylbutane (c) Ans: Prop1-ene (d) Ans: 2,2-Dimethylpentane (e) Ans: Pent2-ene (f) Class X Chemistry www.vedantu.com 9 Ans: 3-Methylbut1-ene (g) Ans: 2,3-Dichloropentane (h) Ans: 2-Methylheptane (i) Ans: But2-ene (j) Class X Chemistry www.vedantu.com 10 CH 3 − C = C − CH 2CH 2CH 2CH 3 Ans: Hept2-ene (k) Ans: 5,5-Dimethylhexaneal Ans: Pentan2-ol Ans: 4-Methylpentanoic acid (n) Ans: 2-Bromo2-methylbutane (o) Class X Chemistry www.vedantu.com 11 Ans: 1-Bromo3-methylbutane (p) Ans: Prop1-ene (q) Ans: Methane-al (r) Ans: Prop1-ene (s) Class X Chemistry www.vedantu.com 12 Ans: Propan1-ol (t) Ans: Ethanoic acid (u) Ans: Ethanal (v) Class X Chemistry www.vedantu.com 13 Ans: 1,2-Dichloroethane 2. Write the structures of the following compounds: (a) Prop-1-ene Ans: (b) 2,3-dimethylbutane Ans: (c) 2-methylpropane Ans: Class X Chemistry www.vedantu.com 14 (d) 3-hexene Ans: CH 3CH 2CH = CHCH 2CH 3 (e) Prop-1-yne Ans: (f) 2-methylprop-1-ene Ans: (g) Alcohol with molecular formula C4H10O Ans: Class X Chemistry www.vedantu.com 15 3. Choose the correct answer: (a) C5H11 is an (i) alkane (ii) alkene (iii) alkyne (iv) alkyl group Ans: Alkyl group (b) A hydrocarbon of the general formula CnH2n is (i) C15H30 (ii) C12H26 (iii) C8H20 (iv) C6H14 Ans: C15H30 (c) The total number of different carbon chains that four carbon atoms from in alkane is (i) 5 (ii) 4 (iii) 3 (iv) 2 Ans: 2 (d) CH3-CH2-OH and CH3-O-CH2 are Class X Chemistry www.vedantu.com 16 (i) Position isomers (ii) Chain isomers (iii) homologous (iv) functional group isomers Ans: functional group isomers (e) The IUPAC name of the compound is (i) 3-trimethylhexane (ii) 3-methyl hexane (iii) 4-methyl hexane Ans: 3-trimethylhexane 4. Fill in the blanks. (a) Propane and ethane are……..(homologous, isomers) Ans: Homologous (b) A saturated hydrocarbon does not participate in a/an ……….reaction (substitution, addition) Ans: Substitution (c) Succeeding members of homologous series differ by………… (CH2, CH, CH3) Ans: CH2 Class X Chemistry www.vedantu.com 17 (d) As the molecular masses of hydrocarbons increase, their boiling points……… and melting points……….. (increase, decrease) Ans: increase (e) C25H52 and C50H102 belong to ……… homologous series (the same, different) Ans: Same (f) CO is an ………… compound. (organic, inorganic) Ans: Inorganic compound (g) The chemical properties of an organic compound are largely decided by the……… and the physical properties of an organic compound are largely decided by the …….. (functional group, number of carbon atom) Ans: Functional group, number of carbon chain (h) CHO is the functional group of an ……….. (alcohol, aldehyde) Ans: Aldehyde (i) The root in the IUPAC name of an organic compound depends upon the number of carbon atoms in ………. (any chain, principal chain) Ans: Principal chain (j) But 1-ene and but-2-ene are examples of ……… isomerism (chain, position, functional) Ans: Position 5. Define or explain chain isomerism and position isomerism with examples in each case. Class X Chemistry www.vedantu.com 18 Ans: Chain isomerism arises due to the difference in arrangement of C atoms in the chain. For example, there are two isomers of butane, C4H10. In one of them, the carbon atoms lie in a straight chain whereas in the other the chain is branched. Position isomerism is due to the difference in position of functional groups. For example, there are two structural isomers with the molecular formula C3H7Br. In one of them, the bromine atom is on the end of the chain, whereas in the other it is attached in the middle. 6. (a) Define the term isomerism. State two main causes of isomerism. Ans: Compounds having the same molecular formula but different structural formula are known as isomers and the phenomenon as isomerism. Two main causes of isomerism. Difference is the mode of linking of atoms. Difference in the arrangement of atoms or groups in space. (b) Draw the chain isomers of hexane (C6H14). Ans: Class X Chemistry www.vedantu.com 19 (c) Draw position isomers of butene (C4H8) Ans: 7. Draw structural formula for each of the following compounds: (a) isomer of n-butane Ans: CH3-CH2-CH2-CH3 (b) Vinegar Ans: Class X Chemistry www.vedantu.com 20 (c) 2-Propanol Ans: CH3-CH (OH)-CH3 (d) Ethanal Ans: CH3-CHO (e) Acetone Ans: CH3-C (O)-CH3 (f) Diethyl ether Ans: CH3-CH2-O-CH2-CH3 What is used to describe these compounds together? Ans: These compounds together can be called organic compounds. 8. (a) What is the special feature of the structure of: (i) Ethene Ans: Ethene possesses a double bond. The two carbon atoms in ethene relate to each other with a double bond. (ii) Ethyne Ans: Ethene possesses a triple bond. The two carbon atoms in ethene are connected with each other with a triple bond. (b) What type of reaction is common to both of the above compounds? Why methane does not undergo this type of reaction. Ans: The above compounds undergo addition reactions. Methane does not undergo this type of reaction due to the absence of unsaturated bonds (double and triple). (C) What is the IUPAC name of dimethyl ether. Class X Chemistry www.vedantu.com 21 Ans: Methoxymethane 9. Which type of reaction will (i) Ethane (ii) Ethene Undergoes? Ans: Ethene undergoes addition reactions with reagents whereas ethane undergoes substitution reactions. 10. Choosing only words from the following list. Write down appropriate words to fill in the blanks from (a) to (e) given below: Addition, carbohydrates, CnH2n-2, CnH2n, CnH2n+2, electrochemical homologous, hydrocarbon, saturated, substitution, unsaturated. The alkane from an (a) …….. Series with the general formula (b) ……… The alkanes are (c)..........(d) ………….which generally undergoes (e)..........reactions. Ans: (a) Electrochemical homologous (b) CnH2n+2 (c) saturated (d) hydrocarbon (e) Substitution 11. Draw the structural formula of a compound with two carbon atoms in each of the following cases. Class X Chemistry www.vedantu.com 22 (a) An alkane with a carbon to carbon single bond. Ans: CH3-CH3 (b) An alcohol containing two carbon atoms. Ans: CH3-CH2OH (c) An unsaturated hydrocarbon with a carbon to carbon triple bond. Ans: H − C ≡ C − H 12. Ethane, ethene, ethanoic acid, ethyne, ethanol from the above, name (a) The compound with -OH as the part of its structure. Ans: Ethanol (b) The compound with -COOH as the part of its structure. Ans: Ethanoic acid (C) Homologue of homologous series with general formula CnH2n. Ans: Ethene 13. Give the correct IUPAC name and the functional group for each of the compounds whose structural formulae are given below: (a) Class X Chemistry www.vedantu.com 23 Ans: IUPAc name: Propanoic acid Functional group: -COOH (b) Ans: IUPAc name: Propanol Functional group: -OH 14. Copy and complete the following table which relates to three homologous series of hydrocarbons: General Formula CnH2n CnH2n-2 CnH2n+2 IUPAc name of the homologous series Characteristic Single bonds bond type IUPAC name of the first member of the series Type of reaction Addition with chlorine Ans: General Formula CnH2n CnH2n-2 CnH2n+2 Class X Chemistry www.vedantu.com 24  IUPAc name of the homologous Alkenes Alkyne Alkane series Characteristic Double bond Triple bond Single bonds bond type IUPAC name of the first member Ethene Ethyne Ethane of the series Type of reaction Addition Addition Substitution with chlorine 15. Fill in the blanks with the correct words from the brackets: (a) Alkenes are the (i) ……… (analogous/homologous) series of (ii) …… (saturated/unsaturated) hydrocarbons. They differ from alkanes due to the presence of (iii) ………. (double/single) bonds. Alkenes mainly undergo (iv) ………. (additional/substitution) reactions. Ans: (i) Homologous (ii) unsaturated hydrocarbons (iii) Single (iv) Addition (b) The organic compound which undergoes substitution reaction is (v) ………. (C2H2, C2H4, C10H18, C2H6) Ans: C2H6 (c) Draw the structural formulae of the two isomers of Butane. Give the correct IUPAC name of each isomer. Class X Chemistry www.vedantu.com 25 Ans: n-Butane and 2-Methylpropane 16. Name: (a) The saturated hydrocarbon containing two carbon atoms. Ans: Ethane (b) An alcohol with three carbon atom. Ans: Propan1-ol (c) A triple bond hydrocarbon with two carbon atoms. Ans: Ethyne Exercise- 12B 1. State the sources of alkanes. Ans: Oil and natural gas are the most prominent sources of alkanes. 2. Methane is a greenhouse gas. Comment Ans: Natural gas is primarily composed of methane. It absorbs the earth's outgoing heat radiation and hence contributes to the greenhouse effect. Class X Chemistry www.vedantu.com 26 3. Give the general formula of the alkanes. Ans: The general formula for alkanes is CnH2n+2, where n is the number of carbon atoms. 4. Draw the structures of isomers of: (a) Butane Ans: Common name: n-Butane IUPAC name: Butane Common name: iso Butane IUPAC name: 2-Methylpropane (b) Pentane. Write the IUPAc and common name of these isomers. Ans: Class X Chemistry www.vedantu.com 27 Common name: n-pentane IUPAC name: Pentane Common name: iso-pentane IUPAC name: 2-Methylbutane Common name: neo-pentane IUPAC name: 2,2-Dimethylpropane 5. Write the (a) molecular formula. (b) Electron dot formula and (c) Structural formula of methane and ethane. Class X Chemistry www.vedantu.com 28 Ans: (a) Molecular formula Methane- CH4 Ethane- C2H6 (b) Electron dot formula Methane- Ethane- (c) Structural formula Methane- Class X Chemistry www.vedantu.com 29 Ethane- 6. How is: (a) Methane and (b) Ethane prepared in the laboratory? Ans: (a) Laboratory preparation of methane The gas produced when a mixture of sodium ethanoate and soda lime is cooked in a hard glass test tube is methane. Water is displaced downwards to collect it. CH3COONa + NaOH + CaO → Na2CO3 + CH4 (at 3000C) (b) Ethane prepared in laboratory When a solution of sodium propionate and soda lime is heated in a boiling tube, ethane gas is produced. Water is also displaced downward, which collects it. C2H5COONa + NaOH + CaO → Na2CO3 + C2H6 (at 3000C) 7. How are methane and ethane prepared from methyl iodide and ethyl bromide? Class X Chemistry www.vedantu.com 30 Ans: CH3I + 2[H] → CH4 + HI C2H5Br + 2[H] → C2H6 + HBr 8. What is a substitution reaction? Give the reaction of chlorine with ethane and name the product formed. Ans: A substitution reaction occurs when one of a molecule's atoms is replaced by another atom or group of atoms. C2H6 + Cl2 → C2H5Cl + HCl 9. Name the compounds formed when methane burns in: (a) Sufficient air (b) insufficient air Give a balanced equation. Ans: (a) The product formed will be carbon dioxide and water CH4 + 2O2 → CO2 + 2H2O (b) The product formed will be carbon monoxide and water 2CH4+ 3O2 (insufficient) → 2CO + 4H2O 10. Write the names and the formula of the products formed when: (a) methane (b) ethane reacts with (i) chlorine (ii) bromine Write the chemical equations: Class X Chemistry www.vedantu.com 31 Ans: Methane reacts with chlorine CH4 + Cl2 → CH3Cl + HCl Methane reacts with Bromine CH4 + Br2 → CH3Br + HBr Ethane reacts with Chlorine C2H6+ Cl2 → C2H5Cl + HCl Ethane reacts with Bromine C2H6 + Br2 → C2H5Br + HBr 11. Name the compound prepared from: (a) Sodium propionate (b) Methyl iodide and (c) Ethyl bromide. Write a balanced equation for the same. Ans: (a) C2H5COONa + NaOH + CaO → Na2CO3 + C2H6 (b) CH3I + 2[H] → CH4 + HI (c) C2H5Br + 2[H] → C2H6 + HBr 12. Write the equation for the complete combustion of Class X Chemistry www.vedantu.com 32 (i) Methane Ans: CH4 + 2O2 → CO2+ 2H2O (ii) Ethane Ans: 2C2H6 + 5O2 → 4CO2 + 2H2O 13. Convert: (a) Methane into chloroform. Ans: CH4+ Cl2 → CH3Cl + HCl CH3Cl + Cl2 → CH2Cl2+ HCl CH2Cl2 + Cl2 → CHCl3 + HCl (b) Sodium acetate into methane Ans: CH3COONa + NaOH → Na2CO3 + CO2 (c) Methyl iodide into ethane. Ans: 2CH3I + 2Na + dry ether → C2H6 + NaI (d) Methane to methyl alcohol Ans: CH4 + O2 + → 2CH3OH (at 120 atm and 475K) 14. Give three uses of: (a) Methane Ans: Methane is a carbon monoxide and hydrogen source. Class X Chemistry www.vedantu.com 33  It's used to make carbon tetrachloride from ethyne methane chloromethane. It is used as a household fuel. (b) Ethane Ans: It's used to make ethane ethanol and ethanol. It produces ethyl chloride, which is utilised in the production of tetraethyllead. It's also a source of energy. 15. Under what conditions does ethane get converted to: (a) Ethyl alcohol Ans: Ethyl alcohol is created when a combination of ethane and oxygen is compressed to around 120 atm pressure and pushed through copper tubes at 475K. 2C2H6 + O2 + → 2C2H5OH (at 120 atm and 475K) (b) Acetaldehyde Ans: Acetaldehyde is produced when a combination of ethane and oxygen is passed through heated molybdenum oxide. C2H6 + O2 + MoO → CH3CHO + H2O (c) Acetic acid Ans: C2H5OH + O2 + Pt → CH3COOH + H2O 16. Using appropriate catalysts, ethane can be oxidised to an alcohol, an aldehyde and an acid. Name the alcohol, aldehyde and acid formed when ethane is oxidised. Class X Chemistry www.vedantu.com 34 Ans: Alcohol- Ethanol (C2H5OH) Aldehyde- Ethanal (CH3CHO) Acid- Ethanoic acid (CH3COOH) Excercise- 12C 1. Write: (a) molecular formula (b) electron dot formula and (c) structural formula of ethene (ethylene). Ans: (a) C2H4 (b) (c) 2. The molecules of alkene family are represented by a general formula CnH2n. Answer the following: (a) What do n and 2n signify? Ans: Alkanes have the generic formula CnH2n+2, where n is the number of carbon atoms in the molecule and 2n+2 is the number of hydrogen atoms. Class X Chemistry www.vedantu.com 35 (b) What is the name of alkene when n=4? Ans: Butene (c) What is the molecular formula of alkene when n=4? Ans: C4H8 (d) What is the molecular formula of the alkene if there are ten H atoms in it? Ans: C5H10 (e) What is the structural formula of the third member of the alkene family? Ans: CH2=CH-CH3 (f) Write the molecular formula of lower and higher homologous of an alkene which contains four carbon atoms. Ans: Lower homologous of alkene which contains four carbons is C3H6 Higher homologues of alkene which contain four carbons is C5H10 3. (a) Distinguish between the saturated hydrocarbon ethane and the unsaturated hydrocarbon ethene by drawing their structural formulae. Ans: Ethane- Ethene- Class X Chemistry www.vedantu.com 36 (b) Draw the structures of isomers of butene and write their IUPAC names. Ans: CH3-CH2-CH=CH2 But −1− ene CH3-CH=CH-CH3 But −2− ene CH2=C(CH3)-CH3− methyl propene 4. Give a balanced equation for the lab. Preparation of ethylene. How is the gas collected? Ans: CH3-CH2OH + H2SO4 → CH3-CH2HSO4 + H2O CH3-CH2HSO4 excess H2SO4 → CH2=CH2 + H2SO4 (at 1600C) The gas is collected by downward displacement of water. 5. How is ethene prepared by: (a) dehydrohalogenation reaction? (b) dehydration reaction? Give equations and name the products formed. Ans: (a) Dehydrohalogenation is an elimination reaction in which a hydrogen halide is removed from a substrate. C2H5Cl + alc. KOH → C2H4 + KCl + H2O Ethene is formed as a product. Class X Chemistry www.vedantu.com 37 (b) C2H5OH + Al2O3 → C2H4 + H2O (at 3000C) Ethene is formed as a product. 6. (a) Ethene when reacts with halogens (chlorine and bromine) from saturated products. Name them and write balanced equations. Ans: CH2=CH2 + Cl2 → CH22(Cl)-CH2(Cl) - 1,2-Dichloroethane CH2=CH2 + Br2 → CH2(Br)-CH2(Br) - 1,2-Dibromoethane (b) Give the conditions and the main product formed by hydrogenation of ethene. Ans: When ethene and hydrogen travel through a finely divided catalyst, such as platinum or palladium at room temperature or nickel at 200o C, the two hydrogen atoms are added to the unsaturated molecule, resulting in a saturated one. C2H4 + H2 + Ni → C2H6 (at 2000C) 7. Convert ethanol into ethene using (a) Solid dehydrating agent (b) hot conc. H2SO4? Give only balanced equations. Ans: (a) C2H5OH + Al2O3 → C2H4 + H2O (at 3000C) (b) CH3-CH2HSO4 excess H2SO4 → CH2=CH2 + H2SO4 (at 1600C) 8. Write the following properties of ethene: (a) Physical state Class X Chemistry www.vedantu.com 38 Ans: Gaseous state. (b) Odour Ans: Sweetish odour (c) Density as compared to air Ans: Density lesser than air. (d) Solubility Ans: sparingly soluble in water but soluble in organic solvents. 9. How would you convert: (a) ethyl bromide into ethene Ans: C2H5Br + alc. KOH → C2H4 + KBr + H2O (b) ethene into 1,2-dibromoethane Ans: CH2=CH2 + Br2 → CH2 (Br)-CH2(Br) (c) ethene into ethane 10. Give balanced equation when: (a) ethene is burnt in excess of oxygen. Ans: C2H4 + 3O2 → 2CO2+ 2H2O + heat Class X Chemistry www.vedantu.com 39 (b) ethene reacts with chlorine gas. Ans: CH2=CH2 + Cl2 → CH2(Cl)-CH2(Cl) (c) ethene combines with hydrogen chloride. Ans: CH2=CH2 + HCl → CH3-CH2Cl (d) a mixture of ethene and hydrogen is passed over nickel at 2000C. Ans: C2H4 + H2 + Ni → C2H6 (at 2000C) 11. Give the formula and names of A, B,C and D in the following equations: Ans: (a) A- CH3Cl (chloro methane) B-CH2Cl2 (Di-chloromethane) C-CHCl3 (tri-chloro methane) D- CCl4 (Carbon tetrachloride) (b) A- C2H4 (ethene) B- C2H6 (ethane) C-C2H5Br (bromo-ethane) D- C2H4Br2 (1,2-Di-bromoethane) (c) B- H2 (Hydrogen) Class X Chemistry www.vedantu.com 40 12. Write the name and formula of the product formed in each case below: (a) C2H4 + Cl2 → ………. Ans: 1,2-di-chloroethane (C2H4Cl2) (b) C2H5I + KOH (alc.) → ………… Ans: Ethene (C2H4) (c) H2C=CH2 + alk. KMnO4 → …….. Ans: Ethane1,2di-ol (CH2(OH)-CH2(OH)) (d) H2C=CH2 + HBr→…….. Ans: Bromoethane (CH5Br) 13. What do you observe when ethene is passed through alkaline KMnO4 solution? Ans: H2C=CH2 + alk. KMnO4 → CH2(OH)-CH2(OH) Ethane1,2di-ol will be formed. 14. Name three compounds formed by ethene and give one use of each compound. Ans: polythene, Ethanol, and Epoxyethane are formed by ethene. Carrying bags are made of polythene. Ethanol is a beginning element for a variety of different items, mostly cosmetics and toiletries. preparation. Epoxyethane is a chemical that is used to make detergents. Class X Chemistry www.vedantu.com 41 Exercise- 12D 1. What are the sources for alkynes? Give the general formula of alkynes. Ans: Alkynes can be found in natural gas and petroleum. Alkynes have the general formula: CnH2n-2 2. Give an example of isomers shown by triple bond hydrocarbons (alkynes) and write their IUPAC names. Ans: Isomers shown by triple bond hydrocarbons is Butyne. Isomers are shown below: But1-yne But2-yne 3. How is ethyne prepared in the laboratory? (a) Draw a diagram Ans: (b) Give an equation Ans: CaC2 + 2H2O → Ca(OH)2 + C2H2 Class X Chemistry www.vedantu.com 42 (c) How is pure dry gas collected? Ans: Because the pure dry gas is insoluble in water, it is collected by water displacement downward. 4. Give the method of preparation of ethyne by: 1,2-dibromoethane. Ans: CH2(Br)-CH2(Br) + Alc. KOH → C2H2 + 2KBr + 2H2O 5. Name the hydrocarbon which: (a) is a tetrahedral molecule. Ans: Methane is a tetrahedral molecule. (b) Is a planar molecule. Ans: Ethene is a planar molecule. (c) Is a linear molecule. Ans: Ethyne is a linear molecule. (d) forms a red precipitate with ammoniacal solution of copper (I) chloride. Ans: Ethyne forms a red precipitate with ammoniacal solution of copper (I) chloride. (e) Is known as paraffin. Ans: Saturated hydrocarbons or alkanes are known as paraffin. (f) Is known as olefin. Ans: Alkenes are known as olefin. (g) a compound which will give ethyne (acetylene) gas when treated with water. Class X Chemistry www.vedantu.com 43 Ans: When calcium carbide is exposed to water, it produces acetylene gas. 6. Classify the following compounds as alkanes, alkenes and alkynes: C3H4, C3H8, C5H8, C3H6 Ans: C3H8 and C3H6 are alkanes. C3H4 and C5H8 are alkynes. 7. Give a chemical test to distinguish between (a) Saturated and unsaturated compounds. Ans: When bromine water is added to an unsaturated compound, bromine water is ejected in a red-brown colour. As a result, if an organic chemical decolorizes bromine water, it is an unsaturated hydrocarbon with a double or triple bond. Alkanes, which are saturated hydrocarbons, do not decolorize bromine water. (b) Ethane and ethene. Ans: In two separate test tubes, dissolve ethane and ethene in carbon tetrachloride solution. Fill the two test tubes with bromine gas. If the colour of bromine gas changes, the gas is ethene; if the colour remains the same, the gas is ethane. (c) Ethene (ethylene) and ethyne (acetylene). Ans: Pass the gas through an ammoniacal cuprous chloride solution. Ethene will not form any ppt while ethyne will form red colour ppt. 8. Compound X is bubbled through bromine dissolved in CCl4; Class X Chemistry www.vedantu.com 44 (a) Draw the structure of X. Ans: (b) State your observation during the reaction. Ans: Bromine solution will be decolourised. 9. Give balanced equations for the following conversions: (a) An alkene to an alkane Ans: CH2 + CH2 + Ni + H2 → CH3CH3 (at 3000C) (b) An alkene to an alcohol Ans: CH2=CH2 + H2O → CH2CH2OH (c) An alkyne to an alkene. Ans: C2H2 + H2 + lindar’s reagent → C2H4 10. Name the products formed and write an equation when ethyne is added to the following in an inert solvent: (a) chlorine Class X Chemistry www.vedantu.com 45 Ans: 1,2-dichloro ethene and 1,1,2,2 -tetrachloro ethane will be formed. C2H2 + Cl2 → C2H2Cl2 + Cl2 → C2H2Cl4 (b) Bromine Ans: ,2-dibromo ethene and 1,1,2,2 -tetrabromo ethane will be formed. C2H2 + Br2 → C2H2Br2 + Br2 → C2H2Br4 (c) Iodine Ans: 1,2-di-iodoethene will be formed. C2H2 + I2 → C2H2I2 (d) Hydrogen Ans: C2H2 + H2 + Ni → C2H6 (e) Excess of hydrochloric acid. Ans: C2H2 + HCl → C2H2Cl2 11. Substitution reactions are characteristic reactions of ……… (alkynes/alkenes/alkanes). Ans: Alkanes 12. (a) Write an equation for the laboratory preparation of (i) An unsaturated hydrocarbon from calcium carbide. Ans: CaC2 + H2O → C2H2 + Ca(OH)2 (ii) An alcohol from ethyl bromide. Class X Chemistry www.vedantu.com 46 Ans: CH3CH2Br + aq. KOH → CH3CH2OH (b) What would you see, when ethyne is bubbled through a solution of bromine in carbon tetrachloride? Ans: When bromine in carbon tetrachloride is introduced to ethyne, the colourless ethylene bromide is formed, and the orange colour of the bromine fades. (c) Name the addition product formed between ethene and water. Ans: Ethanol (C2H5OH) 13. Give reasons: (a) Ethyne is more reactive than ethene. Ans: Because of the presence of a triple bond between its two carbon atoms, ethyne is a more reactive molecule than ethene. (b) Ethene is more reactive than ethane. Ans: Because of the presence of a double bond between its two carbon atoms, ethane is a more reactive chemical than ethene. (c) Hydrocarbons are excellent fuels. Ans: Alkanes, for example, are hydrocarbons that react with oxygen to produce carbon dioxide and water vapour. Because alkanes are combustible, they make good fuels. 14. (a) Write the balanced equations: (i) when butane is burnt in oxygen Ans: C4H10 + 6O2 → 4CO2 + 5H2O Class X Chemistry www.vedantu.com 47 (ii) preparation of ethylene from ethyl alcohol. Ans: C2H5OH + H2SO4 → C2H4 + H2O (b) (i) Convert ethane to acetic acid Ans: 2C2H6 + O2 + K hot tube → C2H5OH + Pt → CH3COOH (at 3000C) (ii) Convert ethyne to ethane. Ans: C2H2 + H2 + Ni → C2H6 15. (a) Write the equation for the preparation of carbon tetrachloride from methane. Ans: CH4 + Cl2 → CH3Cl + HCl CH3Cl + Cl2 → CH2Cl2 + HCl CH2Cl2 + Cl2 → CHCl3 + HCl CHCl3 + Cl2 → CCl4 + HCl (b) Draw the structural formula of ethyne. Ans: (c) How is the structure of alkynes different from that of alkenes? Ans: Alkynes contain triple bonds while alkenes contain double bonds. Class X Chemistry www.vedantu.com 48 Exercise- 12E 1. (a) What are alcohols? State their sources. Ans: Alcohols are alkane hydroxyl derivatives that are created by replacing one or more hydrogen atoms with an OH group. Methanol comes from the harmful distillation of wood, whereas ethanol comes from sugar fermentation. (b) Give general formulae of monohydric alcohol. Ans: CnH2n+1OH 2. Give the: (a) Dot diagram of first member of alcohol. Ans: (b) Abbreviated formula of third member of alcohol. Ans: CH3CH2CH2OH (c) Structure of second member of the alcohol group. Ans: (d) Structure of alcohol with 4 carbon atoms. Class X Chemistry www.vedantu.com 49 Ans: 3. State the method of preparation of ethanol: (a) By hydrolysis of ethane. Ans: Ethyl hydrogen sulphate is created when concentrated sulphuric acid is added to ethene at a temperature of 80°C and a pressure of 30 atm. Hydrolysis of ethyl hydrogen sulphate with boiling water yields ethanol. C2H4 + H2SO4 → C2H5HSO4 C2H5HSO4 + H2O → C2H5OH + H2SO4 (b) By hydrolysis of ethyl bromide. Ans: The hydrolysis of alkyl halide with a hot dilute alkali can be used to make alcohols. C2H5Cl + KOH → C2H5OH + KCl 4. Halo alkanes reacts with alkalies to produce alcohol. Give the equation for the preparation of second member of homologous series of alcohol. State under what condition the reaction occur. Ans: Alcohol is produced when haloalkanes react with alkalis. Give the formula for the second member of the homologous series of alcohol. Indicate the circumstances in which the reaction occurs. Class X Chemistry www.vedantu.com 50 5. (a) How do the boiling point and melting point change in the homologous series of alcohols? Ans: With increasing molecular mass, the melting and boiling points of subsequent members of the homologous series of alcohols rise. (b) Name the product formed when ethanol reacts with acetic acid. Give an equation. Ans: Ethyl acetate is generated when ethanol combines with acetic acid. (c) What is the name given to this type of reaction? Ans: Esterification is the name given to this process. 6. Complete and balance the following equations. State the conditions wherever necessary. CH (a) ||| + H 2 → _____ + H 2 → ____ CH Ans: C2H2 + H2 → C2H4 + H2 → C2H6 (b) C2H4 + Br2 → ………… Ans: C2H4 + Br2 → CH2(Br)-CH2(Br) (c) C2H4 + HCl →……….. Ans: C2H4 + HCl → CH3CH2Cl (d) CaC2+ H2O → ………. Ans: CaC2 + H2O → Ca(OH)2 + C2H2 (e) C2H2 + Br2 → ………… Class X Chemistry www.vedantu.com 51 Ans: C2H2 + Br2 → H(Br)C=C(Br)H (f) C2H5OH + [O] + K2Cr2O7 →……… Ans: C2H5OH + [O] + K2Cr2O7 → CH3COOH 7. What is the effect of ethanol on human body? Ans: Moderate ethanol intake lowers stress levels and boosts emotions of happiness and well-being, as well as lowering the risk of coronary heart disease. Heavy drinking, on the other hand, can lead to addiction and raise the risk of all forms of harm and trauma. 8. How are the following obtained: (a) Absolute alcohol Ans: By distilling wet alcohol with benzene, absolute alcohol can be obtained. The mixture of water and benzene distils away, leaving behind anhydrous alcohol. (b) Spurious alcohol Ans: It's made through faulty distillation. It's a blend of alcohol with a lot of methanol in it. (c) Methylated spirit Ans: Ethyl alcohol is mixed with 5% methyl alcohol, a coloured dye, and some pyridine to make denatured alcohol. 9. Name the products formed and give appropriate chemical equations for the following: (a) Sodium reacting with ethyl alcohol. Class X Chemistry www.vedantu.com 52 Ans: When sodium interacts with ethyl alcohol, hydrogen is produced, and sodium ethoxide is formed. C2H5OH + 2Na → 2C2H5ONa + H2 (b) Ethanol oxidised by acidified potassium dichromate. Ans: Alcohols are oxidised and transformed to ethanal, which is then turned to acetic acid. C2H5OH + [O] → CH3CHO CH3CHO + [O] → CH3COOH 10. Give the trivial (common) names and the IUPAC names of the following: (a) C3H6 Ans: Common name: Propylene IUPAC: Propane (b) C2H4 Ans: Common name: ethylene IUPAC name: ethene (c) C2H2 Ans: Common name: acetylene IUPAC name: ethyne (d) CH3OH Ans: Common name: methyl alcohol IUPAC name:methanol Class X Chemistry www.vedantu.com 53 (e) C2H5OH Ans: Common name: ethyl alcohol IUPAC name: ethanol 11. Ethanol can be oxidised to ethanoic acid. Write the equation and name the oxidising agent. Ans: CH3CH2OH + [O] + K2Cr2O7 → CH3COOH + H2O 12. Name an organic compound which is: (a) Used for illuminating country houses. Ans: Ethyne (b) Used for making a household plastic material. Ans: Ethyne (c) Called ‘wood spirit’. Ans: Methanol (d) Poisonous and contain OH group. Ans: Methanol (e) Consumed as a drink. Ans: Ethanol (f) Made from water gas. Ans: Methanol Class X Chemistry www.vedantu.com 54 (g) Solvent for gums and resins. Ans: Ethanol (h) Dehydrated to produced ethene. Ans: Ethanol 13. Ethanol can be converted into ethene which can be changed into ethane. Choose the correct word or phrase from the brackets to complete the following sentences. (a) The conversion of ethanol into ethene is an example of………. (dehydration, dehydrogenation). Ans: Dehydration reaction. (b) Converting ethanol into ethene requires the use of ……… (conc. HCl, conc. HNO3, conc. H2SO4). Ans: Conc. H2SO4 (c) The conversion of ethene into ethane is an example of……. (hydration, hydrogenation). Ans: Hydration reaction. (d) The catalyst used in the conversion of ethene into ethane is commonly …………. (iron, nickel, cobalt). Ans: Nickel 14. Write the equations for the following lab, preparations: (a) Ethane from sodium propionate. Class X Chemistry www.vedantu.com 55 Ans: C2H5COONa + NaOH → Na2CO3 + C2H6 (b) Ethene from idoethane. Ans: C2H5I + alc. KOH→ C2H4 + KI + H2O (c) Ethyne from calcium carbide. Ans: CaC2 + H2O → Ca(OH)2 + C2H2 (d) Methanol from idomethane. Ans: CH3I + NaOH → CH3OH + NaI 15. Name the compound prepared by each of the following reactions: (i) C2H5COONa + NaOH → Ans: C2H5COONa + NaOH → Na2CO3 + C2H6 (ii) CH3I + 2H → Ans: CH3I + 2H → CH4 + HI (iii) C2H5Br + KOH (alcoholic solution)→ Ans: C2H5Br + KOH (alcoholic solution)→ C2H4 + KBr + H2O (iv) CO + 2H2 (Zinc oxide catalyst)→ Ans: CO + 2H2 (Zinc oxide catalyst)→ CH3OH (v) CaC2 + 2H2O→ Ans: CaC2 + 2H2O→ Ca(OH)2 + C2H2 16. Write the equations for the following reactions: Class X Chemistry www.vedantu.com 56 (a) Calcium carbide and water. Ans: CaC2 + H2O → Ca(OH)2 + C2H2 (b) Ethene and water (steam). Ans: C2H4 + H2O → C2H5OH (c) Bromoethane and an aqueous solution of sodium hydroxide. Ans: C2H5Br + NaOH → C2H5OH + NaBr Exercise-12F 1. What are carboxylic acids? Give their general formula Ans: Carboxylic acids are found in abundance. Amino acids and fatty acids are two important examples. The carboxylate anion is formed when a carboxylic acid is deprotonated. CnH2n+1COOH is the general formula for carboxylic acids. 2. Write the names of: (a) First three members of carboxylic acid series. Ans: Formic acid, ethanoic acid, and propanoic acid are three members of the carboxylic acid series. (b) Three compounds which can be oxidised directly, or in stages to produce acetic acid. Ans: Ethanol, Acetylene, and Ethanal are three chemicals that can be oxidised directly or in steps to create acetic acid. 3. (a) Give the structural formulae of acetic acid. Class X Chemistry www.vedantu.com 57 Ans: (b) IUPAC name of acetic acid. Ans: Ethanoic acid (c) What is glacial acetic acid? Ans: Glacial acetic acid is pure acetic acid. Because when it cools, it crystallises into ice. 4. Vinegar is greyish in colour with a particular taste. Explain. Ans: Vinegar, often known as Sirka, is a diluted acetic acid solution. It has a greyish appearance due to the presence of colouring matter, and it has the typical taste and flavour due to the presence of other organic acids and organic compounds. 5. Complete: (a) Vinegar is prepared by the bacterial oxidation of…………. Ans: Ethanol (b) The organic acid present in vinegar is ……….. Ans: Acetic acid (c) The next higher homologue of ethanoic acid is ………... Ans: Propanoic acid Class X Chemistry www.vedantu.com 58 6. How is acetic acid prepared from (a) Ethanol Ans: It's made by oxidising ethanol with acidified potassium dichromate in the lab. C2H5OH + K2Cr2O7 →CH3COOH (b) Acetylene Ans: Acetylene is transformed to acetaldehyde first by passing it through a 40 percent H2SO4 solution at 60°C in the presence of 1% HgSO4. At 70°C, acetaldehyde is oxidised to acetic acid in the presence of manganous acetate as a catalyst. C2H2 + H2O + dil.H2SO4 + HgSO4 → CH3CHO CH3CHO + O → 2CH3COOH 7. What do you notice when acetic acid reacts with (a) Litmus Ans: When acetic acid reacts with litmus, the colour changes from blue to red. (b) metals Ans: Hydrogen is produced when acetic acid combines with metals. (c) Alkalies Ans: Salt is formed when acetic acid combines with alkalies. (d) Alcohol Ans: Esters are formed when acetic acid interacts with alcohols. Class X Chemistry www.vedantu.com 59 8. Acetic acid is a typical acid. Write one equation in each case for its reaction with (a) A metal Ans: 2CH3COOH + Zn → (CH3COO)2Zn + H2 (b) A base/alkali Ans: CH3COOH + NaOH → CH3COONa + H2O (c) A carbonate Ans: 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2 (d) A bicarbonate Ans: CH3COOH + NaHCO3 →CH3COONa + H2O + CO2 9. What do you observe when acetic acid is added to (a) Sodium bicarbonate Ans: Carbon dioxide is produced when acetic acid is introduced to sodium bicarbonate. (b) Ethyl alcohol in the presence of sulphuric acid. Ans: The ester (ethyl acetate) is generated when acetic acid is introduced to ethyl alcohol in the presence of sulphuric acid. (c) Neutral FeCl3 solution? Ans: Wine red hue is formed when acetic acid is added to neutral FeCl3. 10. Name: Class X Chemistry www.vedantu.com 60 (a) Compound formed when acetic acid and ethanol react together. Ans: Ethyl acetate is formed when acetic acid and ethanol combine. (b) Reducing agent used to convert acetic acid into ethanol. Ans: Acetic acid is converted to ethanol using lithium aluminium hydride (LiAlH4). (c) Substance used to change acetic acid to acetic anhydride. Ans: Acetic anhydride is formed when phosphorus pentoxide (P2O5) is heated with acetic acid. Miscellaneous 1. (a) Which of the following statements is wrong about alkanes? (i) They are all saturated hydrocarbon. (ii) They can undergo addition as well as substitution reaction. (iii) They are almost non polar in nature. (iv) On complete combustion give out carbon dioxide and water. Ans: (ii) They can undergo only substitution reactions. (b) The organic compound obtained as the end product of the fermentation of sugar solution is: (i) Methanol (ii) Ethanol (iii) Ethane (iv) Methanoic acid Ans: Ethanol Class X Chemistry www.vedantu.com 61 (c) Find the odd one out and explain: C3H8, C5H10, C2H6, CH4 Ans: C5H10 because it is not following the general alkane formula (CnH2n+2). 2. Give chemical equation for: (a) The laboratory preparation of methane from sodium acetate. Ans: CH3COONa + NaOH → CH4 + Na2CO3 (b) The reaction of one mole of ethene with one mole of chlorine gas. Ans: C2H4 + Cl2 → CH2(Cl)-CH2(Cl) (c) The preparation of ethyne from 1,2-dibromoethane. Ans: CH2(Br)-CH2(Br) + 2KOH (alc.) → C2H2 + 2KBr + 2H2O 3. State how the following conversions can be carried out: (a) Ethyl chloride to ethyl alcohol Ans: C2H5Cl + aq. KOH → C2H5OH + KCl (b) Ethyl chloride to ethene Ans: C2H5Cl + alc. KOH → C2H4+ HCl (c) Ethene to ethyl alcohol Ans: C2H4 + H2O + H2SO4 → C2H5OH (d) Ethyl alcohol to ethene Class X Chemistry www.vedantu.com 62 Ans: C2H5OH + H2SO4 → C2H4 4. (a) Define isomerism Ans: The phenomenon of isomerism occurs when two or more compounds have the same chemical formula but distinct chemical structures. (b) Give the IUPAC name of the isomer C4H10 which has a branched chain. Ans: 2-Methylpropane 5. A compound X when treated with an organic acid Y (having vinegar like smell) in the presence of the acid Z, forms a compound P which has a fruity smell. (a) Identify X, Y and Z. Ans: X- alcohol Y- Carbonic acid Z- Sulphuric acid (b) Write structural formula of X and Y. Ans: X= R-OH Y= R-COOH (c) What type of compound is P? Ans: Ester (d) Name the above reaction. Ans: Esterification reaction Class X Chemistry www.vedantu.com 63 (e) If compound x and y both have 2 carbon atoms. Write the reaction. Ans: C2H5OH + CH3COOH + conc. H2SO4 → CH3COOC2H5 + H2O 2010 (a) An organic compound undergoes addition reactions and gives a red colour precipitate with ammoniacal cuprous chloride. Therefore, the organic compound could be: (i) Ethane (ii) Ethene (iii) Ethyne (iv) Ethanol Ans: With ammoniacal cuprous chloride, an organic compound undergoes an addition reaction, resulting in a red colour precipitate. As a result, Ethyne could be an organic substance. (b) An organic weak acid is: (i) Formic acid (ii) Sulphuric acid (iii) Nitric acid (iv) Hydrochloric acid Ans: Formic acid (c) The organic compound mixed with ethanol to make it spurious is (i) Methanol (ii) Methanoic acid (iii) Methanal Class X Chemistry www.vedantu.com 64 (iv) Ethanoic acid Ans: Methanol (d) Draw the structural formula for each of the following: (i) Ethanoic acid Ans: (ii) But-2-yne Ans: H 3C − C ≡ C − CH 3 (e) Compound A is bubbled through bromine dissolved in carbon tetrachloride and the product is CH2Br-CH2Br. (i) Draw the structural formula of A. Ans: (ii) What type of reaction has A undergone? Ans: Addition reaction (iii) What is your observation? Ans: Compound A will decolourise the bromine water. Class X Chemistry www.vedantu.com 65 (iv) Name (not formula) the compound formed when steam reacts with A in the presence of phosphoric acid. Ans: Ethanol (v) What is procedure for converting the product of (e) (iv) back to A? Ans: Dehydration- By heating it (ethanol) at 170 degrees Celsius with strong sulphuric acid. 2011 (a) The functional group present in acetic acid is: (i) Ketonic >C=O (ii) Hydroxyl -OH (iii) Aldehyde -CHO (iv) Carboxyl -COOH Ans: Carboxyl -COOH (b) The unsaturated hydrocarbons undergo: (i) A substitution reaction (ii) An oxidation reaction (iii) An addition reaction (iv) None of the above Ans: Addition reaction (c) The number of C-H bonds in ethane molecule are: (i) Four (ii) Six Class X Chemistry www.vedantu.com 66 (iii) Eight (iv) Ten Ans: Six (d) Choose the correct word/phrase from within the brackets to complete the following sentences: (i) The catalyst used for conversion of ethene to ethane is commonly …………. (nickel/iron/cobalt) Ans: Nickel (ii) When acetaldehyde is oxidized with acidified potassium dichromate, it forms………… (ester/ethanol/acetic acid) Ans: acetic acid (iii) Ethanoic acid reacts with ethanol in the presence of concentrated H2SO4, so as to form a compound and water. The chemical reaction which takes place is called………….. (dehydration/hydrogenation/esterification) Ans: Esterification (iv) Write the equation for the reaction taking place between 1,2- dibromoethane and alcoholic potassium hydroxide. Ans: (v) The product formed when ethene gas reacts with water in the presence of sulphuric acid………….(ethanol/ethanal/ethanoic acid) Ans: Ethanol (e) Write balanced chemical equations for the following: (i) Monochloro ethane is hydrolysed with aqueous KOH. Ans: CH3Cl + aq.KOH → CH3OH + KCl Class X Chemistry www.vedantu.com 67 (ii) A mixture of sodalime and sodium acetate is heated. Ans: CH3COONa + NaOH + CaO → CH4 + Na2CO3 (iii) Ethanol under high pressure and low temperature is treated with acidified potassium dichromate. Ans: C2H5OH + K2Cr2O7 → CH3COOH (iv) Water is added to calcium carbide. Ans: CaC2 + H2O → Ca(OH)2+ C2H2 (v) Ethanol reacts with sodium at room temperature. Ans: CH3OH + Na → CH3ONa + 2H2 2012 (a) Give the structural formula for the following: (i) Methanoic acid Ans: (ii) Ethanal (iii) Ethyne Class X Chemistry www.vedantu.com 68 Ans: HC ≡ CH (iv) Acetone (v) 2-methyl propane Ans: (b) From the following organic compounds given below, choose one compound in each case which relates to the description [i] to [iv]: [ethyne, ethanol,acetic acid, ethene, methane]. (i) An unsaturated hydrocarbon used for welding purposes. Ans: Ethyne (ii) An organic compound whose functional group is carboxyl. Ans: Acetic acid (iii) A hydrocarbon which on catalytic hydrogenation gives a saturated hydrocarbon. Ans: Ethene (iv) An organic compound used as a thermometric liquid. Class X Chemistry www.vedantu.com 69 Ans: Ethanol (C) (i) Why is pure acetic acid known as glacial acetic acid ? Ans: Because it solidifies just below room temperature, pure ethanoic acid is referred to as glacial ethanoic acid. (ii) Give a chemical equation for the reaction between ethyl alcohol and acetic acid. Ans: CH3COOH + C2H5OH + conc. H2SO4 → CH3COOC2H5 + H2O 2013 (a) (i) Give a chemical test to distinguish ethene gas and ethane gas. Ans: In two separate test tubes, dissolve ethane and ethene in carbon tetrachloride solution. Fill the two test tubes with bromine gas. If the colour of bromine gas changes, the gas is ethene; if the colour remains the same, the gas is ethane. (ii) Identify the statement that is incorrect about alkanes: (A) They are hydrocarbons. (B) There is a single covalent bond between carbon and hydrogen. (C) They can undergo both substitution as well as addition reactions. (D) On complete combustion they produce carbon dioxide and water. Ans: C is incorrect. Alkanes can undergo only substitution reactions. (b) Give the structural formula for the following: (i) An isomer of n-butane Ans: Class X Chemistry www.vedantu.com 70 (ii) 2-propanol Ans: 2014 (a) The IUPAC name of the acetylene is: (i) Propane (ii) Propyne (iii) ethene (iv) ethyne Ans: Ethyne (b) Name hydrocarbons containing >C=O functional group. Ans: Carbonyl compounds. (c) Give preparation of ethane from sodium propionate. Ans: C2H5COONa + NaOH + CaO → C2H6 + Na2CO3 (d) Distinguish ethane and ethene (using alkaline potassium permanganate solution). Class X Chemistry www.vedantu.com 71 Ans: The purple colour of potassium permanganate does not fade in ethane, whereas the purple colour fades in ethene. (e) Give the structural formula of the following: (i) ethanol (ii) 1-propanal (iii) ethanoic acid (iv) 1,2, dichloroethane Ans: (f) Give preparation of ethanol from monochloroethane and aq. Sodium hydroxide. Ans: C2H5Cl + NaOH → C2H5OH + NaCl 2015 Class X Chemistry www.vedantu.com 72 (a) Give balanced chemical equations for the following conversions: (i) ethanoic acid to ethyl ethanoate. Ans: CH3COOH + C2H5OH + conc. H2SO4 → CH3COOC2H5 + H2O (ii) Calcium carbide to ethyne Ans: CaC2+ 2H2O → Ca(OH)2 + C2H2 (iii) Sodium ethanoate to methane. Ans: CH3COONa + NaOH → Na2CO3 + CH4 (b) Using their structural formula identify the functional group by circling them: (i) Dimethyl ether (ii) Propanone Ans: (c) Name the following: (i) Process by which ethane is obtained from ethene Ans: Hydrogenation process. Class X Chemistry www.vedantu.com 73 (ii) A hydrocarbon which contributes towards the greenhouse effect. Ans: Methane (iii) Distinctive reaction that takes place when ethanol is treated with acetic acid. Ans: Esterification reaction (iv) The property of elements by virtue of which atoms of the element can link to each other in the form of a long chain or ring structure. Ans: Catenation (v) Reaction when an alkyl halide is treated with alcoholic potassium hydroxide. Ans: C2H6Cl + alc. KOH → C2H4 (d) Hydrocarbon which is a greenhouse gas is: A. Acetylene B. Ethylene C. Ethane D. Methane Ans: Methane Class X Chemistry www.vedantu.com 74