ICSE Class 10 Chemistry - Section A

Grade X (ICSE) Chemistry Paper - Section A (Multiple Choice & Fill-ins)

• The paper consists of Section A, which is compulsory, and Section B, from which any four questions must be attempted.
• The total marks for the paper are 80, and the time allowed is three hours.
• The first 15 minutes are to be used for reading the paper.

Question 1: Multiple Choice

• If an organic compound's empirical formula is CH2O, then its molecular formula is C6H12O6.
• A nitrogen molecule has a triple covalent bond.
• The O-H bond is more polar than C-H, N-H, or H-H bonds.
• Brass is composed of Zinc (Zn) and Copper (Cu).
• The vapor density of CH3OH is 16.
• Electrolysis of acidified water exemplifies a redox reaction.
• Ammonia (NH3) is a polar covalent compound in a gaseous state that doesn't conduct electricity.
• Zinc (Zn) can displace metal from Iron Sulphate solution.
• Given 10g of H2 versus 12.044x10^23 atoms of He, there are 5 moles of H2.
• Fluorspar is not an ore of aluminum.
• The reaction at the anode during silver electroplating is Ag - 1e- -> Ag+
• Ionization is called oxidation in metals when they lose electrons.
• Sodium (Na) and Calcium (Ca) are extracted only by electrolysis.
• Liquid CCl4 acts as a non-electrolyte.
• The empirical formula shows the simplest whole number ratio of atoms in a compound.

Question 2: Diagram & Fill-ins

• The illustrated process converts alumina to aluminum.
• The electrolyte mixture contains a divalent metal: Magnesium (Mg2+).
• Powdered substance 'X' is sprinkled on the surface of the electrolyte mixture.
• The process is Electrometallurgy.
• The anode reaction (electrode Y) is necessary for continuous replacement.
• Ionization is the process for the formation of ions from molecules.
• Pure water consists almost entirely of molecules.
• Aluminium oxide (Al2O3) reacts with both acids and alkalis to give salt and water.
• A water molecule combines with a hydrogen atom/proton to form a hydronium ion.
• Covalent compounds have low melting points.

Question 3: Matching Statements A-J

• Electrometallurgy is an application of electrolysis where the anode does not diminish in size.
• The anode is the electrode to which cyanide ions of aq. Na[Ag(CN)2] migrate during electrolysis.
• The ion which accepts electrons from the cathode and gets reduced to neutral atoms is Cl-.
• Sucrose is a compound containing molecule only.
• Formic acid or Ammonia is a compound that ionizes in solution but not in a gaseous state.

Question 4: Reasoning

• Copper, silver, and lead are electrorefined, but K, Na, and Ca are not because Copper, silver, and lead are less reactive metals compared to K, Na, and Ca.
• MgCl2 is soluble in water but insoluble in acetone because water is a polar solvent and dissolves polar compounds, while acetone is a nonpolar solvent.
• The fusion temperature of the electrolyte has to be lowered because of electrolytic reduction.
• The blue color of aqueous CuSO4 does not change due to using a copper electrode.
• Magnesium (Mg) loses two electrons from its valence shell in MgO formation.

Question 5: Electroplating

• Sodium argentocyanide is the electrolyte selected for electroplating silver onto a metal article.
• Sodium argentocyanide is a complex salt.
• Sodium argentocyanide is preferred to silver nitrate as an electrolyte because it provides a more even and controlled deposition of silver.
• Maintain a steady current and voltage to ensure a smooth, firm, long-lasting deposit.
• The reaction at the cathode is the reduction of silver ions to silver metal.
• The reaction at the anode involves the oxidation of metal.

Section B

Question 3: Definitions & Applications

• Gay Lussac's Law of Combining Volumes: Gases react in simple whole number ratios by volume, provided temperature and pressure remain constant.
• Vapour Density: The mass of a certain volume of a gas divided by the mass of an equal volume of hydrogen at the same temperature and pressure.
• Cryolite in Aluminium Extraction: Lowers the melting point of alumina.
• Graphite in Aluminium Extraction: Used as the anode, undergoes oxidation to form carbon dioxide.
• Crucible during Electrolysis of Molten Lead Bromide: Made of silica.
• The reaction at the cathode during electrolysis of molten lead bromide produces liquid lead.
• Solid lead bromide cannot be used as an electrolyte because it does not conduct electricity in the solid-state.

Question 4: Table Completion

• At no = 20 and B: At.no = 8 form Ionic Compound and the formula is AB
• At no = 20 and C: At no = 17 form Ionic Compound and the formula is AC2
• D: At no = 12 and E: At no= 16 form Covalent Compound and the formula is DE2

Question 5: Empirical Formula

• Given composition of elements: Zn = 47.8% and Cl = 52.2%, The empirical formula of the compound is ZnCl2
• Chemical bonding occurs because atoms seek to achieve a stable electronic configuration through the duplet (for hydrogen and lithium) or octet rule (for other atoms).
• Carbon tetrachloride is insoluble in water and does not conduct electricity, while sodium chloride is soluble in water and conducts electricity in solution.

Question 6: Formulae & Reactions

• Compound H2Y: Y is a non-metal.
• The nature of the bonding in H2Y is covalent.
• Formula of the compound formed between K and Y is K2Y.
• Formula of the compound formed between Ca and Y is CaY.
• The bulb in Cell A (NaCl solution) glows brightly because NaCl is a strong electrolyte and provides a high concentration of ions. The bulb in Cell B (acetic acid) glows dimly because acetic acid is a weak electrolyte and provides a low concentration of ions. The bulb in Cell C (sugar solution) does not glow because sugar is a non-electrolyte and does not provide ions.
• Reactions in Electrolysis:
  • Acidified CuSO4 with copper electrodes: Cu -> Cu2+ + 2e- (anode), Cu2+ + 2e- -> Cu (cathode)
  • Molten PbBr2 with inert electrodes: 2Br- -> Br2 + 2e- (anode), Pb2+ + 2e- -> Pb (cathode)

Question 7: Calculations

• For a reaction with sulfuric acid to give 78g of fertilizer ammonium sulphate the weight of ammonia gas required for the reaction is: 17g.
• The weight of ammonia gas obtained when 32.6 g of ammonium chloride reacts with calcium hydroxide is 3.4g.
• The molecular formula is C2X2Y4.
• Composition of the resultant mixture after ignition: H2O will be present in the resultant mixture.
• The mass of 50 cc of CO at STP is 0.0625.

Question 8: Naming and Explaining

• A metal present in duralumin and brass, but not in magnalium is Copper.
• A metal present in type metal, but not in solder is Antimony.
• Two impurities in bauxite which remain unaffected when concentrated NaOH solution is added in the metallurgy of aluminum are Iron oxide and Silica.
• A non-metallic element other than carbon, which forms a neutral and an acidic oxide, is hydrogen.
• A metal which on ionization forms Y3+ is Aluminum.
• Impure Bauxite to a sodium salt using an Alkali: Al2O3.2H2O + 2NaOH -> 2NaAlO2 + 3H2O
• Sodium aluminate to an insoluble hydroxide of aluminum: NaAlO2 + 2H2O -> Al(OH)3 + NaOH
• Insoluble hydroxide of aluminum to pure alumina: 2Al(OH)3 -> Al2O3 + 3H2O
• Zinc oxide can be reduced to zinc by using carbon monoxide because it is less electropositive than aluminum.
• Roasting of the ore generally results in evolution of sulphur dioxide gas, while calcination of the ore evolves carbon dioxide gas.

Section A (Alternate Paper)

Question 1A: Multiple Choice

• On moving from left to right across a period of the periodic table, the non-metallic character of the elements Increases.
• An acid which is not a hydracid is H2SO3.
• The catalyst used in the Contact process is Vanadium pentoxide.
• The property of carbon of forming chains and rings is called Catenation.
• Liquid NH3 is employed in a refrigerator because It has a high heat of evaporation.
• Nitrogen gas can be obtained by heating Ammonium nitrite.
• An aqueous solution of HCl gas forms Muriatic acid.
• The acid which can produce carbon from cane sugar is Concentrated Sulphuric acid.
• Ammonia nitrate is used in Preparing explosives.
• During ionization metals lose electrons, this change is called Oxidation.
• Pyrosulphuric acid is the chemical name of Oleum.
• If an element A belongs to period 3 and Group II, then it will have: 3 shells and 2 valence electrons.
• Among the elements of period 2, the element that has high electron affinity is Fluorine.
• Gas liberated when dil. HCl gas is added to iron (II) sulphide is Hydrogen sulphide gas.
• To increase the pH value of neutral solution, we should add An alkali.

Question 1B: Name the Following

• Law of Octaves is the law where every 8th element repeats properties.
• Vulcanization is the process by which Sulphur is boiled with rubber.
• A basic hygroscopic substance is Calcium Chloride.
• An acid which is not an oxidising agent is hydrochloric Acid.
• A catalyst used in Haber's process is Iron.

Question 1C: Match the Following

• Proton - Responsible for nuclear charge
• Normal Salt - Sodium chloride
• Chlorine - Halogen
• Complex Salt - Sodium zincate
• Electron - Occupied sub-shell

Question 1D: Fill in the Blanks

• Concentrated sulphuric acid is valuable in preparing other acids due to its low volatility.
• Each period except Period 1 in the Periodic Table begins with a metal and ends up with a noble gas.
• Vinegar contains Acetic acid.
• A solution X turns blue litmus red, so it must contain hydrogen ions.
• Nitric acid is manufactured by Ostwald's process.

Question 1E: State the Observations

• When ammonia is dissolved in water it forms ammonium hydroxide.
• When sugar is heated with concentrated Sulphuric acid, it turns black.
• When copper oxide is treated with concentrated Hydrochloric acid, it forms a blue-green solution.
• When lead nitrate is treated with dilute Sulphuric acid, a white precipitate of lead sulphate forms.
• When hydrogen chloride gas is passed through silver nitrate solution, a white precipitate of silver chloride forms.

Question 1F: Define

• Ionization Potential: The amount of energy required to remove the most loosely bound electron from an isolated gaseous atom to form a cation
• Acid Salt: A salt that is formed by the partial replacement of hydrogen ions of an acid by a metal.
• Isomerism: The phenomenon in which compounds have the same molecular formula but different structural formulas and properties.
• Base: A substance that can accept hydrogen ions or donate electrons

Section B

Question 2: Gas Preparation

• The gas collected in the jar is Ammonia.
• Balanced equation for the preparation of Ammonia is: NH4Cl + NaOH -> NaCl + H2O + NH3
• Collection Method: The gas is collected by downward displacement or upward delivery.
• The drying agent used is Calcium oxide also known as Quicklime..
• An Ammonia concentrated solution in the jar is indicated by a pungent smell, or by bringing a glass rod dipped in HCl near opening forming ammonium chloride.
• Ammonia Manufacture-The reaction between nitrogen and hydrogen to form ammonia is reversible.
• 1 volume of nitrogen will react with 3 volumes hydrogen.
• The catalyst is finely divided iron, using a promoter such as molybdenum.
• N2(g) + 3H2(g) <-> 2NH3(g) deltaH= -92.2 kl/mol.
• Ammonia can act as a reducing agent - write a relevant equation for such a reaction: 4NH3 + 5O2 --> 4NO + 6H2O

Question 3: Give Reasons

• Magnesium atom is smaller because it has fewer electron shells than calcium.
• Elements with low ionization potential exhibit metallic properties because they can easily lose electrons.
• Hydrochloric is is considered a strong acid because it completely dissociates in water while while acetic is not.
• Hydrogen chloride gas cannot be dried over quick lime because it reacts with calcium oxide.
• Sulphuric acid is Dibasic acid because it has two replaceable hydrogen atoms.
• Ammonia cannot be obtained from ammonium nitrate and sodium hydroxide because it forms nitrate.
• Nitric oxide supports combustion more vigorously because it is rich oxygen. Burning magnesium continues to burn in Nitric while Sulphur is extinguished oxide because it takes oxygen to burn.
• Hydrocarbons are excellent fuels because it releases large amount of heat when burned
• Concentrated sulphuric is called the 'oil’ because it is viscous and very greasy to the touch is called the“oil of vitriol’ because of its oily appearance and corrosive properties.

Section A (Another Paper)

Question 1A: Multiple Choice

• An element of an inorganic compound found in nature is known as: Both mineral and ore.
• An alkaline earth metal is: Calcium.
• A compound that has all three types of bonds (ionic, covalent, coordinate) is: Ammonium chloride.
• The reason for using aluminium in the alloy duralumin is: Aluminium brings lightness.
• The molecule containing a triple covalent bond is: Nitrogen.
• A molecule that has one lone pair of electrons is: Ammonia.
• The particles present in strong electrolytes are: Mainly ions.
• The particle that is not an alloy of Copper is: Duralumin.
• A particular solution contains molecules and ions of the solute, so it is a: Weak acid.
• The process used to convert impure alumina to pure alumina is: Bayer's process.
• A compound that will not produce an acid when made to react with water is: Carbon monoxide.
• The metals - zinc and tin are present in the alloy: Solder.
• With excess of chlorine, Ammonia (NH3) forms: NCl3.
• Sulphide ore is generally concentrated by: Froth flotation process.
• The acid which contains four hydrogen atoms in it is: Acetic acid.

Question 1B: Identify the gases

• The gas evolved when dilute sulphuric acid is added to sodium sulphite is Sulfur Dioxide.
• The gas produced when excess ammonia reacts with chlorine is Nitrogen. The reaction will also produce hydrogen chloride.
• The gas produced when ammonium nitrate is heated is Nitrous Oxide.
• The gas produced when sodium nitrate is heated: Oxygen.
• The gas that turns acidified potassium dichromate clear green is Sulphur Dioxide.

Question 1C: Give Reasons

• Metals are called reducing agents because they lose electrons.
• Acetic acid is a monobasic acid because it has one replaceable hydrogen atom.
• Acids, bases, and salts are classified as electrolytes because they dissociate into ions.
• When stating the volume of a gas, the pressure and temperature should also be apecified because volume is variable given certain conditions.

Question 1D: Match the Following

• Solder - Electrical fuse
• Brass - Decorative articles
• Polar - Chloride Ion
• Cobalt chloride - Pink
• Metal - Aluminium

Question 1E: Define

• Ionisation Potential: energy required to remove an electron from a gaseous atom.
• Electron Affinity: measure of the ability of an atom to accept an electron.
• Empirical Formula: simplest whole number ratio of atoms in a compound.
• Gay Lussac's Law: gases combine in simple volume ratios.
• Avogadro's Law: equal volumes of gases contain equal number of molecules.

Section B: "Attempt any four questions" from Paper

Question 2B:

• A "covalent compound that dissolves in water" is Alcohol.
• “Compound which gives ethyne when water is added" is Calcium carbide.
• “A pair of electrons that does not take part in bonding" Non-bonding pair of electrons.
• “A gas evolved when Aluminium powder is mixed with caustic soda" is Hydrogen (H2).
• “A gas produced on reaction of dil is" Hydrogen.

Question 2C: Fill in the Blanks

• Alkenes are called paraffins because of Little affinity.
• Ethyne reacts with Silver nitrate to form precipitate of Silver acetylide.
• The volume of 44g of CO2 at S.T.P is 22.4L.
• The catalyst used in Contact process is Vanadium
• Heating an ore in a limited supply of air at a temperature just below its melting point is known as Roasting

Question 2D: Identify

• Turns Lead acetate paper black: Hydrogen sulphide (H2S).
• Gives dense white fumes when a rod dipped in Hydrochloric acid solution is brought near it: Ammonia (NH3).

Another Paper

Question 1: "Attempt all questions"

• If an organic compound's empirical formula is CH20, then its molecular formula can be C6H12O6
• A nitrogen molecule has a triple covalent bond.
• The O-H bond is most polar of the set.
• The process of electrolysis acidified water is an example of a redox action.
• There are 5 moles of H2 given 10g of H2
• Calcium is NOT an ore of Aluminum.
• Ag - 1e -> AG at the anode during the process article of electroplating with silver.
• Mg2+ is the divalent electrolyte
• Aluminum does form Y3+ on ionization.
• Ionization means during metals lose electron
• During ionization Metals electrons this oxidation. Oxidation.