Question 1

Question 1(a)Fill in the blanks from the choices given in brackets:(i) The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion is called .............. (electron affinity, ionisation potential, electronegativity)(ii) The compound that does not have a lone pair of electrons is .............. (water, ammonia, carbon tetra chloride)(iii) When a metallic oxide is dissolved in water, the solution formed has a high concentration of .............. ions. (H+, H3O+, OH-)(iv) Potassium sulphite on reacting with hydrochloric acid releases .............. gas. (Cl2, SO2, H2S)(v) The compound formed when ethene reacts with Hydrogen is .............. (CH4, C2H6, C3H8)

Accepted Answer

(i) The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion is called Ionization Potential(ii) The compound that does not have a lone pair of electrons is carbon tetrachloride.(iii) When a metallic oxide is dissolved in water, the solution formed has a high concentration of OH- ions.(iv) Potassium sulphite on reacting with hydrochloric acid releases SO2 gas.(v) The compound formed when ethene reacts with Hydrogen is C2H6.

Question 2

Question 1(d)Write a balanced chemical equation for each of the following:(i) Action of cold and dilute Nitric acid on Copper.(ii) Reaction of Ammonia with heated copper oxide.(iii) Preparation of methane from iodomethane.(iv) Action of concentrated sulphuric acid on Sulphur.(v) Laboratory preparation of ammonia from ammonium chloride.

Accepted Answer

(i) 3Cu + 8HNO3 [dil.] ⟶ 3Cu(NO3)2 + 4H2O + 2NO [g](ii) 2NH3 + 3CuO ⟶ 3Cu + 3H2O + N2 [g](iii)CH3Imethyl iodide+2[H]nascent hydrogen→alcoholZn/Cu coupleCH4methane+HI\underset{	ext{methyl iodide}}{	ext{CH}_3	ext{I}} + \underset{	ext{nascent hydrogen}}{2	ext{[H]}} \xrightarrow[	ext{alcohol}]{	ext{Zn/Cu couple}} \underset{	ext{methane}}{	ext{CH}_4} +	ext{HI}methyl iodideCH3​I​+nascent hydrogen2[H]​Zn/Cu couplealcohol​methaneCH4​​+HI(iv) S + 2H2SO4 (conc.) ⟶ 3SO2 + 2H2O(v) 2NH4Cl + Ca(OH)2 ⟶ CaCl2 + 2H2O + 2NH3

Question 3

Question 1(e)State one relevant observation for each of the following reactions:(i) Addition of ethyl alcohol to acetic acid in the presence of concentrated Sulphuric acid.(ii) Action of dilute Hydrochloric acid on iron (II) sulphide.(iii) Action of Sodium hydroxide solution on ferrous sulphate solution.(iv) Burning of ammonia in air.(v) Action of concentrated Sulphuric acid on hydrated copper sulphate.

Accepted Answer

(i) On warming, the mixture gives fruity smell. Acetic acid on heating with an alcohol and a dehydrating agent [conc. H2SO4] forms an ester — ethyl acetate.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(ii) H2S gas is evolved. It has a foul smell like rotten eggs.FeS + 2HCl [g] ⟶ FeCl2 + H2S(iii) A dirty green precipitate is formed which is insoluble in excess of sodium hydroxide solution.FeSO4 + 2NaOH ⟶ Fe(OH)2↓ (dirty green ppt.) + Na2SO4(iv) Ammonia burns in the atmosphere of excess oxygen with a green or greenish yellow flame, forming nitrogen and water vapour.4NH3 + 3O2 ⟶ 2N2 + 6H2O(v) The blue coloured hydrous copper sulphate changes to white anhydrous copper sulphate as the water of crystallization is removed.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

Question 4

Question 1(f)(i) Draw the structural formula for each of the following:2, 3 – dimethyl butaneDiethyl etherPropanoic acid(ii) From the list of terms given, choose the most appropriate term to match the given description.(calcination, roasting, pulverisation, smelting)Crushing of the ore into a fine powder.Heating of the ore in the absence of air to a high temperature.

Accepted Answer

1. 2, 3 – dimethyl butane :2. Diethyl ether :3. Propanoic acid :(ii) The matching terms are:Crushing of the ore into a fine powder — PulverisationHeating of the ore in the absence of air to a high temperature — Calcination

Question 5

Question 2(b)State the type of Bonding in the following molecules:(i) Water(ii) Calcium oxide

Accepted Answer

(i) Covalent bondingReason — The valency of hydrogen element is 1 and that of oxygen is 2. Hydrogen needs one electrons to attain stable duplet structure of nearest noble gas - He [2] and oxygen needs two electrons to attain stable octet structure of nearest noble gas - Ne [2,8]Each of the two hydrogen atoms shares an electron pair with the oxygen atom such that hydrogen acquires a duplet configuration and oxygen an octet configuration resulting in the formation of two single covalent bonds [H-O-H] in the molecule of water.(ii) Electrovalent bondingReason — The valency of calcium (2,8,8,2) element and that of oxygen (2,6) is 2. Calcium donates two electrons and oxygen takes up those two electrons and electrovalent bond is formed.

Question 6

Question 2(c)Answer the following questions:(i) How will you distinguish between Ammonium hydroxide and Sodium hydroxide using copper sulphate solution?(ii) How will you distinguish between dilute hydrochloric acid and dilute sulphuric acid using lead nitrate solution?

Accepted Answer

(i) With Sodium hydroxide, copper sulphate (CuSO4) solution forms a pale blue precipitate which is insoluble in excess of sodium hydroxide and with ammonium hydroxide it forms a pale blue precipitate which dissolves in excess of ammonium hydroxide and forms a deep/inky blue solution.(ii) Sulphuric acid forms a white precipitate with lead nitrate solution. This precipitate does not dissolve on warming the reaction mixture.H2SO4 (dil.) + Pb(NO3)2 ⟶ 2HNO3 + PbSO4 ↓ [white ppt. formed which does not dissolve on warming the mixture].Hydrochloric acid forms a white precipitate with lead nitrate solution. This precipitate dissolves on warming the reaction mixture so as to form clear solution.2HCl (dil.) + Pb(NO3)2 ⟶ 2HNO3 + PbCl2 ↓ [white ppt. formed which dissolves on warming the mixture].Hence, dilute hydrochloric acid and dilute sulphuric acid can be distinguished using lead nitrate solution.

Question 7

Question 2(d)Identify the salts P and Q from the observations given below:(i) On performing the flame test salt P produces a lilac coloured flame and its solution gives a white precipitate with silver nitrate solution, which is soluble in Ammonium hydroxide solution.(ii) When dilute HCl is added to a salt Q, a brisk effervescence is produced and the gas turns lime water milky. When NH4OH solution is added to the above mixture (after adding dilute HCl), it produces a white precipitate which is soluble in excess NH4OH solution.

Accepted Answer

(i) P is potassium chloride.Reason — K+ ions produces lilac coloured flame and Cl- ions react with silver nitrate to form silver chloride ppt. (soluble in excess of ammonium hydroxide).(ii) Q is zinc carbonate.Reason — CO32- ions produces carbon dioxide with HCl. Zinc chloride forms white ppt. with ammonium hydroxide ( soluble in excess of ammonium hydroxide).

Question 8

Question 3(a)Draw an electron dot diagram to show the formation of each of the following compounds:(i) Methane(ii) Magnesium Chloride[H = 1, C = 6, Mg = 12, Cl = 17]

Accepted Answer

(i) Electron dot diagram showing the formation of Methane is given below:(ii) Electron dot diagram showing the formation of Magnesium chloride is given below:

Question 9

Question 3(b)State the observations at the anode and at the cathode during the electrolysis of :(i) fused lead bromide using graphite electrodes.(ii) copper sulphate solution using copper electrodes.

Accepted Answer

(i) The observations at the anode & at the cathode are:At cathode — silvery grey deposit of lead metal.At anode — reddish brown fumes of bromine vapours.(ii) The observations at the anode & at the cathode are:At cathode — Brownish pink copper metal is deposited at cathode during electrolysis of copper sulphate.At anode — Copper ions are formed. Copper anode diminishes in mass.Blue colour of CuSO4 remains unchanged.

Question 10

Question 3(c)Select the ion in each case, that would get selectively discharged from the aqueous mixture of the ions listed below:(i) SO42-, NO3- and OH- ;(ii) Pb2+, Ag+ and Cu2+.

Accepted Answer

(i) OH- ion will get discharged in preference to SO42- or NO3- ions.(ii) Ag+ ions will get discharged in preference to Pb2+ or Cu2+ ions.

Question 11

Question 5(a)(i) Propane burns in air according to the following equation :C3H8 + 5O2 ⟶ 3CO2 + 4H2O.What volume of propane is consumed on using 1000 cm3 of air, considering only 20% of air contains oxygen.(ii) The mass of 11.2 litres of a certain gas at s.t.p. is 24 g. Find the gram molecular mass of the gas.

Accepted Answer

(i) Given, 20% of air contains oxygen∴ 20% of 1000 cm3 = 20100\dfrac{20}{100}10020​ x 1000 = 200 cm3[By Lussac's law]C3H8+5O2⟶3CO2+4H2O1 vol.:5 vol.⟶3 vol.:4 vol.\begin{matrix} 	ext{C}_3	ext{H}_8 & + & 5	ext{O}_2 &\longrightarrow & 3	ext{CO}_2 & + & 4	ext{H}_2	ext{O} \ 1 	ext{ vol.} & : & 5 	ext{ vol.} & \longrightarrow & 3	ext{ vol.} & : & 4	ext{ vol.} \end{matrix}C3​H8​1 vol.​+:​5O2​5 vol.​⟶⟶​3CO2​3 vol.​+:​4H2​O4 vol.​To calculate the volume of propane consumed :O2:C3H85 vol.:1 vol.200 cm.3:x\begin{matrix}	ext{O}_2 & : & 	ext{C}_3	ext{H}_8 \ 5 	ext{ vol.} & : & 1 	ext{ vol.} \ 200 	ext{ cm.}^3 & : & 	ext{x} \end{matrix}O2​5 vol.200 cm.3​:::​C3​H8​1 vol.x​∴x=15×200=40 cm.3	herefore x = \dfrac{1}{5} 	imes 200 = 40 	ext{ cm.}^3∴x=51​×200=40 cm.3Hence, volume of propane is consumed is 40 cm3(ii) 11.2 lit. weighs 24 g∴ 22.4 lit. will weigh = 2411.2\dfrac{24}{11.2}11.224​ x 22.4 = 48 gHence, gram molecular mass of the gas = 48 g.

Question 12

Question 5(b)A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure:(i) Find the number of moles of hydrogen present.(ii) What weight of CO2 can the cylinder hold under similar conditions of temperature and pressure? (H= 1, C = 12, O = 16)(iii) If the number of molecules of hydrogen in the cylinder is X, calculate the number of CO2 molecules in the cylinder under the same conditions of temperature and pressure.(iv) State the law that helped you to arrive at the above result.

Accepted Answer

(i) 2 g of hydrogen gas = 1 mole∴ 1000 g of hydrogen gas = 10002\dfrac{1000}{2}21000​ = 500 moles.(ii) Molar mass of CO2 = C + 2(O) = 12 + 2(16) = 44 g1 mole of carbon dioxide = 44 g∴ 500 moles of carbon dioxide = 44 x 500 = 22,000 g = 22 kg.Hence, Weight of carbon dioxide in cylinder = 22 kg(iii) According to Avogadro's law — Equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules.∴ molecules in the cylinder of carbon dioxide = X.(iv) Avogadro's law — Equal volume of all gases under similar conditions of temperature and pressure contain equal number of molecules.

Question 13

Question 5(c)Write a balanced chemical equation for the preparation of each of the following salts:(i) Copper carbonate(ii) Ammonium sulphate crystals

Accepted Answer

(i) CuSO4 + Na2CO3 ⟶ Na2SO4 + CuCO3(ii) 2NH4OH + H2SO4 ⟶ (NH4)2SO4 + 2H2O

Question 14

Question 6(a)Give a balanced chemical equation for each of the following:(i) Action of conc. Nitric acid on Sulphur.(ii) Catalytic oxidation of Ammonia.(iii) Laboratory preparation of Nitric acid.(iv) Reaction of Ammonia with Nitric acid.

Accepted Answer

(i) S + 6HNO3 [conc.] ⟶ H2SO4 + 2H2O + 6NO2(ii) 4NH3+5O2→800°CPt.4NO+6H2O+Δ4	ext{NH}_3 + 5	ext{O}_2 \xrightarrow[800 \degree 	ext{C}]{	ext{Pt.}} 	ext{4NO} + 	ext{6H}_	ext{2}	ext{O} + \Delta4NH3​+5O2​Pt.800°C​4NO+6H2​O+Δ(iii) KNO3 + H2SO4 [conc.] →<200°C\xrightarrow{\lt 200 \degree	ext{C}}<200°C​ KHSO4 + HNO3(iv) NH3 + HNO3 ⟶ NH4NO3

Question 15

Question 6(b)Identify the term or substance based on the descriptions given below:(i) Ice like crystals formed on cooling an organic acid sufficiently.(ii) Hydrocarbon containing a triple bond used for welding purposes.(iii) The property by virtue of which the compound has the same molecular formula but different structural formulae.(iv) The compound formed where two alkyl groups are linked by -C-O||\overset{\underset{	ext{||}}{	ext{O}}}{	ext{-C-}}-C-||O​ group.

Accepted Answer

(i) Glacial acetic acid(ii) Ethyne or acetylene(iii) Isomerism(iv) Ketone or Alkanone

Question 16

Question 6(c)Give a balanced chemical equation for each of the following:(i) Preparation of ethane from Sodium propionate(ii) Action of alcoholic KOH on bromoethane.

Accepted Answer

(i) Preparation of ethane from Sodium propionate:C2H5COONasodium propionate+NaOHsodalime→ΔCaOC2H6ethane+Na2CO3\underset{	ext{sodium propionate}}{	ext{C}_2	ext{H}_5	ext{COONa}} + \underset{	ext{sodalime}}{	ext{NaOH}} \xrightarrow[\Delta]{	ext{CaO}} \underset{	ext{ethane}}{	ext{C}_2	ext{H}_6} + 	ext{Na}_2	ext{CO}_3sodium propionateC2​H5​COONa​+sodalimeNaOH​CaOΔ​ethaneC2​H6​​+Na2​CO3​(ii) Action of alcoholic KOH on bromoethane:C2H5-Br Bromoethane [ethyl bromide]+KOH [aq.] alcoholic KOH→boilC2H5OH ethyl alcohol+KBr\underset{	ext{ Bromoethane [ethyl bromide]}}{	ext{C}_2	ext{H}_5	ext{-Br}} + \underset{	ext{ alcoholic KOH}}{	ext{KOH [aq.]}} \xrightarrow{	ext{boil}} \underset{ 	ext{ ethyl alcohol}} {	ext{C}_2	ext{H}_5	ext{OH}} + 	ext{KBr} Bromoethane [ethyl bromide]C2​H5​-Br​+ alcoholic KOHKOH [aq.]​boil​ ethyl alcoholC2​H5​OH​+KBr

Question 17

Question 7(a)Name the following:(i) The process of coating of iron with zinc.(ii) An alloy of lead and tin that is used in electrical circuits.(iii) An ore of zinc containing its sulphide.(iv) A metal oxide that can be reduced by hydrogen.

Accepted Answer

(i) Galvanization(ii) Solder [fuse metal](iii) Zinc blende [ZnS](iv) Copper oxide [CuO]

Question 18

Question 7(b)Answer the following questions with respect to the electrolytic process in the extraction of aluminum:(i) Identify the components of the electrolyte other than pure alumina and the role played by each.(ii) Explain why powdered coke is sprinkled over the electrolytic mixture.

Accepted Answer

(i) Cryolite and fluorspar are components of the electrolyte. Addition of cryolite enhances the conductivity of the mixture since, pure alumina is almost a non-conductor of electricity. Addition of both cryolite & fluorspar lowers the fusion point of the mixture i.e., mixture fuses around 950°C instead of 2050°C.(ii) The layer of powdered coke is sprinkled over the electrolytic mixture as :it prevents burning of carbon electrodes in air at the emergence point from the bath.it minimizes or prevents heat loss by radiation.

Question 19

Question 7(c)Complete the following by selecting the correct option from the choices given:(i) The metal which does not react with water or dilute H2SO4 but reacts with concentrated H2SO4 is ............... (Al/Cu/Zn/Fe)(ii) The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction ............... (Fe/Mg/Pb/Al)(iii) The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is ............... (Al/Na/Mg/K)

Accepted Answer

(i) The metal which does not react with water or dilute H2SO4 but reacts with concentrated H2SO4 is Cu.(ii) The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction — Pb.(iii) The divalent metal whose oxide is reduced to metal by electrolysis of it's fused salt is — Mg.

Solved 2017 Question Paper ICSE Class 10 Chemistry

Section I 40 Marks

Section Ii 40 Marks