Question 1

Question 1(iv)On reaction of magnesium nitride with water, the gas which is liberated is ...............NH3HClH2N2

Accepted Answer

NH3Reason — Reaction of magnesium nitride with water liberates ammonia gas. The reaction is:Mg3N2 + H2O ⟶ MgO + NH3

Question 2

Question 1(v)In an exothermic process, energy is released in the form of heat or light.Which of the following could be exothermic processes?P. Sublimation of camphor crystalsQ. Reaction of water with quick limeR. Dilution of an acidOnly POnly QOnly RBoth Q and R

Accepted Answer

Both Q and RReason — Reaction of water with quick lime and Dilution of an acid, both are exothermic processes. Sublimation of camphor crystals is an endothermic process.

Question 3

Question 1(vi)Percentage of calcium in calcium carbonate (CaCO3) is40304836

Accepted Answer

40Reason —Molecular weight of CaCO3= 40 + 12 + (16 x 3)= 40 + 12 + 48= 100 g100 g of CaCO3 contains 40 g of calciumTherefore, percentage of Ca = 40100\dfrac{40}{100}10040​ x 100 = 40%

Question 4

Question 1(x)The vapour density of carbon dioxide (C = 12 and O = 16) is ...............32164422

Accepted Answer

22Reason — Molecular weight of carbon dioxide = 12 + 2(16) = 12 + 32 = 44 gVapour density of gas =Molecular weight2=442=22 g\dfrac{\text{Molecular weight}}{2} \[0.5em] = \dfrac{44}{2} \[0.5em] = 22 \text{ g}2Molecular weight​=244​=22 gHence, vapour density of carbon dioxide is 22 g

Question 5

Question 1(xiii)Among the given elements, one with least electronegativity islithiumcarbonboronfluorine

Accepted Answer

LithiumReason — Electronegativity increases from left to right. As lithium is on the left side in periodic table hence it has the least electronegativity among the given options.

Question 6

Question 1(xiv)A dry test tube containing lead nitrate is heated. Which of the following would be observed?P. Brown fumes are given out.Q. White coloured residue with yellow fumes are seen.R. Yellow coloured residue is seen.Only POnly QOnly R and QBoth P and R

Accepted Answer

Both P and RReason — On heating, lead nitrate decomposes to form yellow coloured lead oxide, brown coloured fumes of nitrogen dioxide and oxygen as per the below reaction:2Pb(NO3)2 (s) →Δ\xrightarrow{\Delta}Δ​ 2PbO (s) + 4NO2 ↑ + O2 ↑

Question 7

Question 2(v)(a) Give the chemical names and formula of main ores ofaluminiumironzinc(b)	Write the principle metal(s) of the following alloys.BrassStainless steel

Accepted Answer

(a) The chemical names and formula of main ores are given below:S.No.NameChemical NameFormula1.BauxiteHydrated aluminium oxideAl2O3.2H2O2.Red haematiteAnhydrous ferric oxideFe2O33.Zinc blendeZinc sulphideZnS(b) The principle metal(s) of the given alloys are:Copper and Zinc.Iron and Chromium.

Question 8

Question 3(i)Distinguish between the following as directed.(a)	Ethene and ethyne (on the basis of preparation)(b)	Sodium carbonate and sodium sulphite (using dilute hydrochloric acid)

Accepted Answer

(a) Ethene is prepared in laboratory by dehydration of ethyl alcohol using sulphuric acid:C2H5OH ethyl alcohol→170°CConc. H2SO4[excess]C2H4ethene+H2O \underset{	ext{ ethyl alcohol}}{	ext{C}_2	ext{H}_5	ext{OH}} \xrightarrow[170\degree	ext{C}]{	ext{Conc. H}_2	ext{SO}_4	ext{[excess]}} \underset{ 	ext{ethene}}{	ext{C}_2	ext{H}_4} + 	ext{H}_2	ext{O}\ ethyl alcoholC2​H5​OH​Conc. H2​SO4​[excess]170°C​etheneC2​H4​​+H2​O Ethyne is prepared in laboratory by the reaction of calcium carbide and water:CaC2calcium carbide+2H2Owater⟶C2H2ethyne [acetylene]+Ca(OH)2Calcium Hydroxide\underset{	ext{calcium carbide}}{	ext{CaC}_2} + \underset{	ext{water}}{2	ext{H}_2	ext{O}} \longrightarrow \underset{	ext{ethyne [acetylene]}}{	ext{C}_2	ext{H}_2} + \underset{	ext{Calcium Hydroxide}}{	ext{Ca(OH)}_2}calcium carbideCaC2​​+water2H2​O​⟶ethyne [acetylene]C2​H2​​+Calcium HydroxideCa(OH)2​​(b) When Sodium carbonate is treated with dil. HCl, odourless carbon dioxide gas is produced.Na2CO3 + 2HCl ⟶ 2NaCl + H2O + CO2 ↑However, when sodium sulphite is treated with dil.HCl, sulphur dioxide gas with a suffocating odour (burning smell) is produced.Na2SO3 + 2HCl ⟶ 2NaCl + H2O + SO2 ↑

Question 9

Question 3(ii)Draw the electron dot structure for the following.(a)	NaCl(b) MgCl2

Accepted Answer

(a)	NaCl(b) MgCl2

Question 10

Question 3(iii)An element X has atomic number 35. Answer the following questions.(a)	State the period and group to which it belongs.(b)	It is a metal or non-metal?(c) Write a formula between X and hydrogen.

Accepted Answer

(a) The element belongs to group 17 and period 4.Reason — The element X has atomic number 35 and so the electronic configuration will be 2, 8, 18, 7. The number of shells present in an atom determines it's period. Hence, Z will belong to 4th period as it has four shells. The number of valence electrons determines the group and as 7 electrons are present in valence shell hence the element will be in group 17.(b) It is a non-metal.(c) HXStep 1 — Write each symbol with its valencyH1+↗X1−\text{H}^{1+} \phantom{\nearrow} \text{X}^{1-}H1+↗X1−Step 2 — Interchange the valenciesH21 ↘↙ X1⇒H11 ↘↙ X1\overset{\phantom{2}{1}}{\text{H}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{X}} \Rightarrow \underset{\phantom{1}{1}}{\text{H}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{X}} \[0.5em]H21 ↘↙ X1⇒11H​ ↘↙ 1X​Step 3 — Write the interchanged number, ignore equal numbers & hence the formula is : HX\bold{HX}HX

Question 11

Question 4(iii)State one relevant observation for each of the the following reactions.(a)	When hydrogen chloride gas is passed through a solution of sodium thiosulphate.(b)	Concentrated sulphuric acid is added to a solution of potassium nitrate.(c)	When fused lead bromide is electrolysed.

Accepted Answer

(a) When hydrogen chloride gas is passed through a solution of sodium thiosulphate a yellow precipitate of Sulphur can be seen along with water, Sodium chloride, and Sulphur dioxide gas which has a burning smell.Na2S2O3 + 2HCl ⟶ 2NaCl + H2O + SO2 + S ↓(b) Nitric acid is released with a pungent odour when concentrated sulphuric acid is added to a solution of potassium nitrate.KNO3 + H2SO4 (conc.) →<200°C\xrightarrow{\lt 200 \degree	ext{C}}<200°C​ KHSO4 + HNO3(c) At anode, reddish brown fumes of bromine vapours are seen. At cathode, silver grey deposit of lead metal is observed.At cathode:Pb2+ + 2e- ⟶ PbAt anode:Br- ⟶ Br + e-

Question 12

Question 4(iv)Give balanced chemical equations for the following.(a)	Calcium bicarbonate reacts with dilute hydrochloric acid.(b)	Ferric hydroxide with nitric acid.(c)	Zinc nitrate with ammonium hydroxide

Accepted Answer

(a) Ca(HCO3)2 + 2HCl ⟶ CaCl2 + 2H2O + 2CO2(b) Fe(OH)3 + 3HNO3 [dil.] ⟶ Fe(NO3)3 + 3H2O(c) Zn(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Zn(OH)2

Question 13

Question 5(i)The following questions relate to mole concept.(a)	the volume of 320 g of SO2 at STP.(Atomic mass of S = 32 and O = 16)(b)	the mass of 1022 atoms of sulphur.[Atomic mass : S = 32 and O = 16, Avogadro's number (NA) = 6.022 x 1023]

Accepted Answer

Gram molecular mass of SO2 = 32 + 2(16) = 32 + 32 = 64 g64 g of SO2 occupy 22.4 lit of vol at STP∴ 320 g of SO2 will occupy = 22.464\dfrac{22.4}{64}6422.4​ x 320 = 112 lit.Hence, volume of 320 g of SO2 = 112 lit.(b) Gram molecular mass of S = 326.022 × 1023 atoms weigh = 32 g1022 atoms will weigh = 326.022×1023\dfrac{32}{6.022 	imes 10^{23}}6.022×102332​ x 1022 = 0.531 gHence, the mass of 1022 atoms of sulphur = 0.531 g

Question 14

Question 5(iii)The following questions are pertaining to the laboratory preparation of hydrochloric acid.(a)	Name the reactants used during the laboratory preparation of hydrochloric acid.(b)	Give suitable reason for choosing the reactants for laboratory preparation.(c)	Write balanced chemical equation for the reaction taking place below 200°C.

Accepted Answer

(a) Sodium Chloride [NaCl] and Concentrated Sulphuric acid [H2SO4](b) Sodium chloride is preferred as it is cheap and easily available, whereas, conc. sulphuric acid is used as it is non-volatile and has a high boiling point hence it displaces the volatile HCl from the salt sodium chloride.(c) NaCl + H2SO4 (conc.) →<200°C\xrightarrow{\lt 200 \degree	ext{C}}<200°C​ NaHSO4 + HCl

Question 15

Question 5(iv)Give reasons(a)	Liquid ammonia is used as a refrigerant in ice plants.(b)	Only all-glass apparatus should be used for the preparation of nitric acid by heating concentrated sulphuric acid and potassium nitrate.(c)	A piece of wood becomes black when concentrated sulphuric acid is poured on it.

Accepted Answer

(a) Liquid ammonia is a clear, colourless liquid under pressure. It evaporates rapidly and produces cooling effect. Moreover, Ammonia is environmentally compatible, has superior thermodynamic properties and its leaks are easily detectable due to its recognizable odour. All these reasons make liquid ammonia a good refrigerant.(b) All glass apparatus is used in the laboratory preparation of nitric acid since the vapours of nitric acid being highly corrosive attack rubber, cork, etc.(c) A piece of wood becomes black because of the dehydrating property of sulphuric acid. It readily removes elements of water from other compounds.[C6H10O5]n →Conc. H2SO4\xrightarrow{	ext{Conc. H}_2	ext{SO}_4}Conc. H2​SO4​​ 6[C]n + 5[H2O]n

Question 16

Question 6(iii)(a) A compound X having vinegar like smell when treated with ethanol in the presence of the acid, Z, gives a compound Y which has a fruity smell.The reaction isC2H5OH+X→ZY+H2O	ext{C}_2	ext{H}_5	ext{OH} + 	ext{X} \xrightarrow{	ext{Z}} 	ext{Y} + 	ext{H}_2	ext{O}C2​H5​OH+XZ​Y+H2​OIdentify X, Y and Z.Name the above reaction.(b) Name the element in period 3 whose affinity is zero.

Accepted Answer

C2H5OHethyl alcohol+CH3COOHacetic acid→Conc. H2SO4CH3−COO−C2H5ethyl ethanoate+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 ethanoate}}{	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 ethanoateCH3​−COO−C2​H5​​+H2​O(a)X, Y and Z are:X → Acetic acidY → Ethyl acetateZ → Concentrated Sulphuric acidEsterification reaction(b) Argon

Question 17

Question 7(i)If 6 L of hydrogen and 4 L of chlorine are mixed and exploded and if water is added to the gases formed, find the volume of the residual gas.

Accepted Answer

[By Lussac's law]H2+Cl2⟶2HCl1 vol.:1 vol.⟶2 vol.\begin{matrix} 	ext{H}_2 & + & 	ext{Cl}_2 &\longrightarrow & 2	ext{HCl} \ 1 	ext{ vol.} & : & 1 	ext{ vol.} & \longrightarrow & 2	ext{ vol.} \end{matrix}H2​1 vol.​+:​Cl2​1 vol.​⟶⟶​2HCl2 vol.​To calculate the amount of hydrogen used:Cl2:H21 vol.:1 vol.4 lit.:x\begin{matrix}	ext{Cl}_2 & : & 	ext{H}_2 \ 1 	ext{ vol.} & : & 1 	ext{ vol.} \ 4 	ext{ lit.} & : & 	ext{x} \end{matrix}Cl2​1 vol.4 lit.​:::​H2​1 vol.x​∴x=11×4=4 lit.	herefore x = \dfrac{1}{1} 	imes 4 = 4 	ext{ lit.}∴x=11​×4=4 lit.Remaining hydrogen = 6 - 4 = 2 lit.To calculate the amount of HCl :Cl2:HCl1 vol.:2 vol.4 lit.:x\begin{matrix}	ext{Cl}_2 & : & 	ext{HCl} \ 1 	ext{ vol.} & : & 2 	ext{ vol.} \ 4 	ext{ lit.} & : & 	ext{x} \end{matrix}Cl2​1 vol.4 lit.​:::​HCl2 vol.x​∴x=21×4=8 lit.	herefore x = \dfrac{2}{1} 	imes 4 = 8 	ext{ lit.}∴x=12​×4=8 lit.Hence, after reaction 8 lit of HCl is formed which dissolves in water and 2 lit of hydrogen is left.∴ 2 lits. of hydrogen is left.

Question 18

Question 7(ii)Define(a)	Relative molecular mass.(b)	Alkanes.

Accepted Answer

(a) The number of times one atom of an element is heavier than 112\dfrac{1}{12}121​ th the mass of an atom of carbon [C12] is known as the Relative Atomic Mass [RAM] of the element.RAM = Mass of one atom of the element 112th the mass of an atom of carbon \dfrac{	ext{Mass of one atom of the element }}{\dfrac{1}{12} 	ext{th the mass of an atom of carbon }}121​th the mass of an atom of carbon Mass of one atom of the element ​(b) Saturated aliphatic hydrocarbons containing carbon-carbon single bond are known as alkanes. They are also known as paraffins and have the general formula as CnH2n+2

Question 19

Question 7(iii)Choose the role played by different solutions as A, B, C, which is responsible for the observation given in 1 to 3.A. Solution X is a sodium hydroxide solution.B. Solution Y is a weak acid.C. Solution Z is dilute sulphuric acid.(1) Liberate sulphur dioxide from sodium sulphite?(2)	Give a white precipitate with zinc sulphate solution?(3)	Contain solute molecules and ions?

Accepted Answer

(1) C. Solution Z is dilute sulphuric acidNa2SO3 + H2SO4 ⟶ Na2SO4 + H2O + SO2 ↑(2)	A. Solution X is sodium hydroxide solution.ZnSO4 + 2NaOH ⟶ Zn(OH)2 ↓ + Na2SO4(3)	B. Solution Y is a weak acid

Question 20

Question 7(iv)X[2, 8, 8, 1] and Y[2, 8, 18, 7] are two elements. Using this information complete the following:(a) ............... is the metallic element.(b) Formula of the molecule of Y is ...............(c) ............... is bad conductor of electricity.

Accepted Answer

(a) X is the metallic element.Reason — As X has one valence electron, hence it is a metal.(b) Formula of the molecule of Y is Y2.Reason — As Y requires one electron to complete its octet, so two atoms of Y will share one electron each in a covalent bond to form a molecule of Y.(c) Y is bad conductor of electricity.Reason — As Y is a non-metal, hence it is a bad conductor of electricity.

Solved Sample Paper 5

Section A

Section B