Question 1

Question 1(iii)Among the following compounds, identify the compound that has all three bonds (ionic, covalent and coordinate bonds).AmmoniaAmmonium chlorideSodium hydroxideCalcium chloride

Accepted Answer

Ammonium chlorideReason —Covalent bonds: Within the NH4+ ion, the N–H bonds are covalent.Coordinate bond: The lone pair from nitrogen forms a coordinate (dative) bond with a proton (H+) to form the NH4+ ion.Ionic bond: The electrostatic attraction between the NH4+ cation and the Cl- anion constitutes the ionic bond in the crystal.

Question 2

Question 1(v)Which of the following would weigh the most?1 mole of H2O1 mole of CO21 mole of NH31 mole of CO

Accepted Answer

1 mole of CO2Reason — Since each molecule is 1 mole, the weight depends entirely on molar mass.MoleculeMolecular MassH2O1 x 2(H) + 16(C)= 18 g/molCO212(c) + 16 x 2(O)= 44 g/molNH314(N) + 1 x 3(H)= 17 g/molCO12(C) + 16(O)= 28 g/molSo, 1 mole of CO2 has molecular mass of 44 g/mol, hence, weigh the most.

Question 3

Question 1(vii)Assertion (A): Carbon monoxide will not produce an acid when made to react with water?Reason (R): Carbon monoxide is a neutral oxide.Both A and R are true and R is the correct explanation of A.Both A and R are true but R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is the correct explanation of A.Reason — Carbon monoxide (CO) is classified as a neutral oxide; it does not react with either acids or bases and, consequently, does not form an acidic or basic solution in water. Under ordinary conditions there is no reaction:CO + H2O ⟶ no acid formedTherefore the assertion (A) is true, and the reason (R) correctly explains why CO fails to produce an acid with water.

Question 4

Question 1(ix)Nitrogen gas can be obtained by heatingAmmonium nitrateAmmonium nitriteMagnesium nitrideAmmonium chloride

Accepted Answer

Ammonium nitriteReason — When ammonium nitrite (NH4NO2) is heated, it decomposes to form nitrogen gas (N2) and water vapour (H2O). This is a thermal decomposition reaction.NH4NO2 →Δ\xrightarrow{\Delta}Δ​ N2 + 2H2OThe other substances do not furnish nitrogen gas on simple heating at laboratory temperatures:Ammonium nitrate mainly produces nitrous oxide (N2O) and water.Magnesium nitride does not decompose to N2; it yields ammonia when treated with water.Ammonium chloride sublimes rather than decomposes to nitrogen.

Question 5

Question 1(x)Which of the following figures correctly describes electrorefining ?

Accepted Answer

Reason — Electrolytic refining is a process by which metals containing impurities are purified electrolytically to give a pure metal. Option 2 shows the set-up used for electrolytic refining of copper:Anode – impure copper block (loses electrons and goes into solution).Cu - 2e- ⟶ Cu2+Cathode – thin sheet of pure copper (gains mass as metal is deposited).Cu2+ + 2e- ⟶ CuElectrolyte – acidified aqueous CuSO₄ solution.As current passes, pure copper is transferred from the impure anode to the cathode, while insoluble impurities collect below the anode as "anode mud".

Question 6

Question 1(xi)Assertion (A): The RMM of a gas is 64, then its vapour density is 32.Reason (R): RMM is twice the vapour density.Both A and R are true and R is the correct explanation of A.Both A and R are true but R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is the correct explanation of A.Reason — Vapour density (V.D.) is related to relative molecular mass by:V.D.= Relative molecular mass2	ext{V.D.} = \dfrac{	ext{ Relative molecular mass}}{2}V.D.=2 Relative molecular mass​Substituting the given value:V.D.=622=32	ext{V.D.} = \dfrac{62}{2} = 32V.D.=262​=32Thus the assertion is correct. Because the reason states the same relationship—“The RMM is twice the vapour density”—it correctly explains why the vapour density is 32.

Question 7

Question 1(xv)The alkaline earth metal of period 3 is:MgCaNaK

Accepted Answer

MgReason — Alkaline earth metals are the elements in Group 2 of the periodic table. These include Be, Mg, Ca, Sr, Ba, Ra.ElementGroupPeriodTypeMg23Alkaline earth metalCa24Alkali earth metal, butpresent in period 4Na13Alkali metalK14Alkali metalSo, the alkaline earth metal of period 3 is Mg ( Magnesium )

Question 8

Question 2(i)During electrolysis of an aqueous solution of sulphuric acid between platinum electrodes, two types of anions migrate towards the anode but only one of them is discharged.(a) Name the two anions.(b) Name the main product of the discharge of anion at the anode and write the anode reaction.(c) Name the product at the cathode and write the reaction.(d) Do you notice any change in colour. Explain.(e) Why is this electrolysis considered as an example of catalysis?

Accepted Answer

(a)Hydroxide ions (OH-) (from water)Sulphate ions (SO42-) (from H2SO4)(b)The anion discharged: Hydroxide ion (OH-)Product at anode: Oxygen gas (O2)Reaction at anode:4OH- - 4e- ⟶ 4OH4OH ⟶ 2H2O + O2(c)Product at cathode: Hydrogen gas (H2)The reaction at cathode:4H+ + 4e- ⟶ 4H2H + 2H ⟶ 2H2(d) No change in colour is observed. The gases produced hydrogen and oxygen are colourless and the solution remains colourless since H2SO4 and water are both colourless.(e) Water in pure state consists almost entirely of molecules. It is a polar covalent compound and can form ions when traces of dilute sulphuric acid is added. As dilute sulphuric acid catalyses this ionisation, hence this electrolysis of acidified water is considered as an example of catalysis.

Question 9

Question 2(v)Give the structural formula of the following:(a) diethyl ether(b) 1-propanal(c) acetone(d) 1, 2, dichloroethane(e) ethanoic acid

Accepted Answer

(i)	Diethyl ether(ii) 1-propanal(iii) Propanone [acetone](iv) 1, 2, dichloroethane(v) ethanoic acid

Question 10

Question 3(i)An element Z has atomic number 16. Answer the following questions:(a) State the period and group to which Z belongs.(b) What kind of a compound is formed between Z and hydrogen ?

Accepted Answer

(a) The element belongs to 3rd period.Reason — The element Z has atomic number 16 and so the electronic configuration will be 2, 8, 6. The number of shells present in an atom determines it's period. Hence, Z will belong to 3rd period as it has three shells.(b) H2Z

Question 11

Question 3(ii)M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context answer the following:(a) What kind of combination (bond) exists between M and O?(b) How many electrons are there in the outermost shell of M?

Accepted Answer

(a) Electrovalent bond exits between M and O because the bond is formed between a metal and non-metal due to oppositely charged ions.(b) Number of electrons in the outer most shell of M is 1. It is so because the valency of O is -2 and as 2 atoms of M combine with O to form M2O, hence we can say that M has 1 valence electron.

Question 12

Question 3(iv)Name the kind of particles present in:(a) Carbonic acid(b) Sulphuric acid(c) Carbon tetrachloride

Accepted Answer

S.No.CompoundParticles present(a)Carbonic acid (H2CO3)Molecules (H2CO3) and ions (H+, HCO3-, CO32-)(b)Sulphuric acid (H2SO4)Ions (H+ and SO42-)(c)Carbon tetrachloride(CCl4)Molecules (CCl4) only

Question 13

Question 4(ii)Prepare: Lead sulphate from lead carbonate.

Accepted Answer

The first step is to convert insoluble lead carbonate into soluble lead nitrate by treating lead carbonate with dilute nitric acid.PbCO3 (s) + 2HNO3(dil) ⟶ Pb(NO3)2 (aq) + H2O (l) + CO2In the second step, the resulting solution is then treated with sulphuric acid or sodium sulphate solution and a white precipitate of lead suphate is obtained.Pb(NO3)2 + 2NaCl ⟶ 2NaNO3 + PbCl2

Question 14

Question 4(iv)Give one equation each to show the following properties of sulphuric acid:(a) Dehydrating property(b) Acidic nature(c) As a non-volatile acid

Accepted Answer

(i) CuSO4.5H2O→Conc. H2SO4CuSO4 [White Anhydrous]+5H2O	ext{CuSO}_4	ext{.5H}_2	ext{O} \xrightarrow{	ext{Conc. H}_2	ext{SO}_4} 	ext{CuSO}_4 	ext{ [White Anhydrous]} + 5	ext{H}_2	ext{O}CuSO4​.5H2​OConc. H2​SO4​​CuSO4​ [White Anhydrous]+5H2​O(ii) Na2SO3 + H2SO4 (dil.) ⟶ Na2SO4 + H2O + SO2(iii) NaNO3+H2SO4[conc.]→<200°CNaHSO4+HNO3	ext{NaNO}_3 + 	ext{H}_2	ext{SO}_4 [	ext{conc.}]\xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_	ext{4} + 	ext{HNO}_\bold{3}NaNO3​+H2​SO4​[conc.]<200°C​NaHSO4​+HNO3​

Question 15

Question 5(iv)The diagram given alongside is to prepare Iron(III) chloride in the laboratory. Look at the diagram and answer the questions given below :(a) What is substance B?(b) What is the purpose of B ?(c) Why is iron (III) chloride to be stored in a closed container ?

Accepted Answer

(a) Substance B is fused calcium chloride.(b) Iron (III) chloride is highly deliquescent so it is kept dry with the help of B [fused calcium chloride (drying agent)](c) Iron[III] chloride is to be stored in a closed container because iron (III) chloride is highly deliquescent and it absorbs moisture from the surrounding air to form a saturated solution.

Question 16

Question 6(i)Give balanced equations for the following:(a) Laboratory preparation of nitric acid.(b) Preparation of ethanol from monochloroethane and aq, sodium hydroxide.

Accepted Answer

(a)KNO3[conc.]+H2SO4[conc.]→<200°CKHSO4[acid salt]+HNO3\underset{[	ext{conc.}]}{	ext{KNO}_3} + \underset{[	ext{conc.}]}{	ext{H}_2	ext{SO}_4} \xrightarrow{\lt 200 \degree	ext{C}} \underset{[	ext{acid salt}]}{	ext{KHSO}_4} + 	ext{HNO}_3[conc.]KNO3​​+[conc.]H2​SO4​​<200°C​[acid salt]KHSO4​​+HNO3​(b)C2H5-Cl monochloroethane+NaOH[aq] aq. sodium hydroxide→boilC2H5-OH Ethanol [ethyl alcohol]+NaCl \underset{	ext{ monochloroethane}}{	ext{C}_2	ext{H}_5	ext{-Cl}} + \underset{ 	ext{ aq. sodium hydroxide}}{	ext{NaOH[aq]}} \xrightarrow{	ext{boil}} \underset{ 	ext{ Ethanol [ethyl alcohol]} }{	ext{C}_2	ext{H}_5	ext{-OH}} + 	ext{NaCl}\ monochloroethaneC2​H5​-Cl​+ aq. sodium hydroxideNaOH[aq]​boil​ Ethanol [ethyl alcohol]C2​H5​-OH​+NaCl

Question 17

Question 6(ii)(a) The vapour density of a gas is 8. What would be the volume occupied by 24.0 g of the gas at STP?(b) A vessel contains X number of molecules of hydrogen gas at a certain temperature and pressure. How many molecules of nitrogen gas would be present in the same vessel under the same conditions of temperature and pressure?

Accepted Answer

(a)Given, V.D. = 8Gram molecular mass = V.D. x 2 = 8 x 2 = 16 g.16 g occupies 22.4 lit.∴ 24 g. will occupy = 22.416\dfrac{22.4}{16}1622.4​ x 24 = 33.6 lit.Hence, volume occupied by gas = 33.6 lit.(b) According to Avogadro's law, equal volume of all gases under similar conditions of temperature and pressure contain equal number of molecules.Hence, number of molecules of N2 = Number of molecules of H2 = X

Question 18

Question 7(i)(a) Name the other ion formed when ammonia gas dissolves in water.(b) Give one test that can be used to detect the presence of the ion produced.(c) Name the gaseous product formed when dilute nitric acid is added to copper.

Accepted Answer

(a) Hydroxyl ion [OH-].(b) The red litmus paper turns blue due to the presence of hydroxyl ion in the solution.(c) Nitric oxide (NO).

Question 19

Question 7(ii)Write balanced equations for the following reactions:(a) Preparation of ethyne from ethylene dibromide.(b) Preparation of ester using carboxylic acid.(c) Conversion of alkyl halide to ethene.

Accepted Answer

(a)(b) C2H5OHethyl alcohol+CH3COOHacetic acid→Conc. H2SO4CH3−COO−C2H5ethyl acetate+H2O\underset{	ext{ethyl alcohol}}{	ext{C}_2	ext{H}_5	ext{OH}} + \underset{	ext{acetic acid}}{	ext{CH}_3	ext{COOH}} \xrightarrow{	ext{Conc. H}_2	ext{SO}_4} \underset{	ext{ethyl acetate}}{	ext{CH}_3-	ext{COO}-	ext{C}_2	ext{H}_5} + 	ext{H}_2	ext{O}ethyl alcoholC2​H5​OH​+acetic acidCH3​COOH​Conc. H2​SO4​​ethyl acetateCH3​−COO−C2​H5​​+H2​O(c)C2H5-Cl Chloroethane [ethyl chloride]+KOH [aq.] alcoholic KOH→boilC2H4 Ethene [ethylene]+KCl+H2O\underset{	ext{ Chloroethane [ethyl chloride]}}{	ext{C}_2	ext{H}_5	ext{-Cl}} + \underset{	ext{ alcoholic KOH}}{	ext{KOH [aq.]}} \xrightarrow{	ext{boil}} \underset{	ext{ Ethene [ethylene]} }{	ext{C}_2	ext{H}_4} + 	ext{KCl} +	ext{H}_2	ext{O} Chloroethane [ethyl chloride]C2​H5​-Cl​+ alcoholic KOHKOH [aq.]​boil​ Ethene [ethylene]C2​H4​​+KCl+H2​O

Question 20

Question 7(iii)State your observations in each of the following:(a) Dilute hydrochloric acid is added to calcium hydrogen carbonate.(b) At the cathode, acidified aqueous copper sulphate solution is electrolysed with copper electrodes.(c) Moist starch iodide paper is introduced into chlorine gas.(d) Calcium hydroxide is heated with ammonium chloride crystals.

Accepted Answer

(a) When dilute hydrochloric acid is added to calcium hydrogen carbonate, carbon dioxide gas is released with effervescence, and a solution of calcium chloride is formed along with water.(b) Copper, a brownish pink metal is deposited at the cathode when acidified aqueous copper sulphate solution (CuSO4) is electrolysed with copper electrodes.(c) The moist starch iodide paper turns blue-black when exposed to chlorine gas.(d) When calcium hydroxide is heated with ammonium chloride crystals, the pungent smelling gas (ammonia) is given out.

Model Paper 1

Section I 40 Marks

Section Ii 40 Marks