Chemistry Exam Paper 2024-2025 PDF

# LA MARTINIERE FOR BOYS, KOLKATA ## REHEARSAL EXAMINATION 2024-25 ### SUBJECT: CHEMISTRY ### CLASS: X ### TIME: 2 hrs. + 15 min. (Reading time) ### FULL MARKS: 80 Answer to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. Thi...

# LA MARTINIERE FOR BOYS, KOLKATA ## REHEARSAL EXAMINATION 2024-25 ### SUBJECT: CHEMISTRY ### CLASS: X ### TIME: 2 hrs. + 15 min. (Reading time) ### FULL MARKS: 80 Answer to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of the paper is the time allowed for writing the answers. Attempt all questions from section A and any four questions from section B. The intended marks of questions or parts are given in ( ). ## SECTION A [Attempt all questions] ### Question 1. Choose one correct answer to the questions from the given options. (Write the correct answer clearly). (15) #### (i) In the electrolysis of dilute common salt, Hydrogen is obtained at cathode because P: Hydrogen ions have higher concentration than sodium ions. Q: Sodium ions have lesser tendency to get reduced than hydrogen ions. R: Sodium is solid and Hydrogen is a gas. **(a) Only P** **(b) Only Q** **(c) Only R** **(d) Both P and R** #### (ii) An element reacts with hot concentrated aqueous alkali to evolve hydrogen. The metal can be : **(a) Sodium** **(b) Aluminium** **(c) Iron** **(d) Copper** #### (iii) Dilute HCl can be chemically distinguished from dilute HNO3 using: **(a) BaCl2 solution** **(b) AgNO3 solution** **(c) MnO2 powder** **(d) FeSO4 solution** #### (iv) A metal X conducts electricity but cannot displace hydrogen from dilute hydrochloric acid X + 2HCI ------------> No reaction Which particles are responsible for the conduction of electricity in the above solution? **(a) X atoms** **(b) X2+ ions** **(c) X2 molecules** **(d) Free electrons** #### (v) Assertion(A) : Concentrated Sulphuric acid reacts with Ethanol to produce a gas which decolourises bromine water because. Reason (R): Concentrated sulphuric acid is a drying agent. **(a) Both A and R are true and R is the correct explanation of A.** **(b) Both A and R are true and R is not the correct explanation of A** **(c) A is true but R is false.** **(d) A and R are false** #### (vi) The compound which is a non electrolyte is **(a) Glycerol** **(b) Sulphuric acid** **(c) Acetic acid** **(d) Formic acid** #### (vii) C4H6 belongs to the homologous series of **(a) Alkanes** **(b) Alkenes** **(c) Alkynes** **(d) Alcohols** #### (viii) The number of hydrogen atoms present in one molecule of the hydride of an element whose atomic number is 13 **(a) 1** **(b) 3** **(c) 5** **(d) 6** #### (ix) C-12, C-13 and C-14 are the three isotopes of Carbon and C-12 is placed in period 2 and group 14 in the periodic table. What will be the position of C-13 with respect to C-12 **(a) to its left** **(b) to its right** **(c) below it** **(d) at the same place** #### (x) A soluble salt of which metal will give a white precipitate with NaOH solution but not with NH4OH solution? **(a) Copper** **(b) Calcium** **(c) Zinc** **(d) Lead** #### (xi) Which electronic configuration suits the most non reactive element? **(a) 2** **(b) 2,5** **(c) 2,8,7** **(d) 2, 8,8,1** #### (xii) Assertion(A): Halogens form uni-negative ions Reason(R): After gaining one electron halogens achieve an octet and stability. **(a) Both A and R are true and R is the correct explanation of A.** **(b) Both A and R are true but R is not the correct explanation of A.** ***(c) A is true but R is false.*** **(d) Both A and R are false** #### (xiii) The ratio between the number of atoms in 2.24 litre of Nitrogen gas and 0.4 g of Helium gas is: (At. wt. of N = 14, He = 4) **(a) 1:1** **(b) 1:2** **(c) 3:1** **(d) 2:1** #### (xiv) The catalyst used in Habers process for the manufacture of NH3 is : **(a) Platinum.** **(b) Chromic oxide.** **(c) Finely divided Iron.** **(d) Vanadium pentoxide.** #### (xv) Which of the following is true about ammonium salts: **(a) All are insoluble** **(b) All are explosives** **(c) All gives ammonia gas with alkalis** **(d) All give nitrogen gas with acids** ### Question 2 #### (i) Sanjay wanted to electrorefine an impure block of Copper. **(a) What should he connect to the negative terminal of the battery?** **(b) What should he connect to the positive terminal of the battery?** **(c) Name the electrolyte he needs to use.** **(d) Write the reaction taking place at the cathode.** **(e) Write the reaction taking place at the anode** (5) #### (ii) Match the following Column A with Column B. (5) | Column A | Column B | | ----------- | ----------- | | (a) Universal indicator | (1) Funnel arrangement | | (b) Ammonium hydroxide | (2) Dehydrating agent | | (c) Froth floatation | (3) PH indicator | | (d) Hydrochloric acid | (4) Heavy impurities | | (e) Sulphuric acid | (5) Weak electrolyte | #### (iii) Complete the following by choosing the correct answers from the bracket: (5) **(a) An element with one electron in the valence shell is likely to be (reducing / oxidising) agent.** **(b) Sodium hydroxide does not form (basic / normal) salt.** **(c) (Copper / Lead) hydroxide is soluble in excess of ammonium hydroxide but insoluble in sodium hydroxide.** **(d) Ethane undergoes (Substitution / Addition) reaction to form Chloroethane.** **(e) pH of Hydrochloric acid will be (higher / lower) than oxalic acid.** #### (iv) Identify the following: (5) **(a) The type of bond formed when a metal bonds with a nonmetal** **(b) The method used to concentrate an ore containing lighter impurities.** **(c) The type of reaction that converts an alkyne to an alkane** **(d) The energy released by a neutral gaseous atom when it accepts an electron.** **(e) The reaction occurring at cathode** #### (v) (a) Draw the structure of the following organic compounds : (3) (1) 2-Methylbutanoic acid (II) 2,2- Dimethylpentane (III)1,1,2,2-Tetrabromoethane (b) Write the IUPAC name of the following Organic compounds : (2) (I) CH3-CH-CH=CH-CH3 | CH3 (II) CH3-CH-CH2-CH=O | CH3 ## SECTION B [Attempt any Four questions] ### Question 3. #### (I) Identify the reactant and write balanced equation for the following: (2) Dilute hydrochloric acid reacts with compound Q to give FeCl2 and Hydrogen sulphide gas. #### (ii) What property of sulphuric acid is exhibited in each of the following: (2) **(a) Blue vitriol converted to anhydrous copper sulphate** **(b) Converting Sodium nitrate to Nitric acid** #### (iii) How will you chemically distinguish between the following: (3) **(a) Copper(II) oxide and Manganese dioxide.** **(b) Dilute Sulphuric acid and Concentrated Sulphuric acid.** **(c) Sodium carbonate and Sodium Sulphite** #### (iv) Give balanced chemical equation for the following reactions: **(a) Excess Ammonia and Chlorine.** **(b) Ethyne and Chlorine in CCI4.** **(c) Sulphur and Concentrated Nitric acid.** ### Question 4 #### (i) Mr. Sen is the director of a chemical factory which manufacture Nitric acid on a large scale. (7) **(a) Name the process used.** **(b) Give balanced chemical equation of step I.** **(c) State the temperature and the catalyst required in step I.** **(d) How is the temperature maintained initially in step I.** **(e) Give balanced chemical equation of each of the steps II and III separately.** #### (ii) What do you observe in the following cases: (3) **(a) Ethene gas is passed through Bromine in CCl4.** **(b) HCI acid added to Pb(NO3)2 solution.** **(c) NaOH solution added to FeCl3 solution.** ### Question 5 #### (i) Mr. Saha is the owner of an Aluminium industry which extract Aluminium from Bauxite **(a) Name the process used to concentrate impure Bauxite ore.** **(b) Give balanced chemical equation of each of the three steps used in the above process and state the temperature required in each case.** (3) **(c) Write the composition of the electrolyte used in Hall Heroult's process.** (1) **(d) Write the electrolytic dissociation reaction and the reactions taking place at the cathode and anode during the electrolytic reduction of alumina.** (3) #### (ii) (a) What is an amalgam? (1) **(b) State the composition of the alloy Stainless Steel.** (1) ### Question 6 #### (i) Explain what is meant by the statement " The Vapour density of CO2 is 22 ". (2) #### (ii) The chemical analysis of an Inorganic compound revealed that it contains Na = 14.31%, S = 9.97%, H = 6.22% and O = 69.5%. The molecular mass of the compound is found to be 322. Determine the empirical formula of the compound. If all the hydrogen is present in combination with oxygen as water of crystallization, determine the molecular formula of the compound). (4) (At.wts. of Na= 23, S=32, O = 16, H = 1 ) #### (iii) Ramesh obtained 1.12 litres of oxygen gas at N.T.P by heating 69.4 gm of an impure sample of Pb3O4. The equation for the reaction is as follows : 2Pb3O4 -------> 6PbO + O2 Determine the percentage purity of the impure sample of Pb3O4. (At.wts. of Pb = 207, O = 16) #### (iv) Give the anode reaction for the electrolysis of the following: **(a) Dilute NaCl solution using graphite electrodes.** **(b) Sodium argentocyanide solution using Ag electrodes.** (2) ### Question 7 #### (i) Write balanced chemical equation for the laboratory preparation of the following: (3) **(a) Methane** **(b) Ethanol** **(c) Ethyne** #### (ii) **(a) Write the structural formula of the organic compounds having molecular formula C4H10 that shows chain isomerism.** (1) **(b) Write the structural formula of the organic compounds having molecular formula C4H6 that shows position isomerism.** (1) #### (iii) Name the final product formed and also give its structural formula when Ethanol is heated with a mixture of K2Cr2O7 and Concentrated H2SO4. (2) #### (iv) Give balanced chemical equation for the following reactions: (3) **(a) Ethanol and metallic Sodium.** **(b) Ethanoic acid and Calcium hydroxide.** **(c) Complete combustion of Ethane.** ### Question 8 #### (i) Rahul wants to prepare Ammonia gas in the laboratory: (5) **(a) Name the reactants he needs to use.** **(b) Give balanced chemical equation for the reaction.** **(c) How will he dry Ammonia gas?** **(d) How will he finally collect Ammonia gas?** #### (ii) Give one reason for the following : (3) **(a) A graphite anode is preferred to Platinum anode during the electrolysis of molten Lead bromide.** **(b) Pure Nitric acid is colourless but the Nitric acid prepared in the laboratory is slightly yellowish brown in colour.** **(c) Hydrogen chloride gas fumes in moist air.** #### (iii) Compare Carbon tetrachloride and Sodium chloride with regard to solubility in water and electrical conductivity. (2)