Q: Question 10Give a balanced equation for thermal dissociation of(i) a gas(ii) a solid [both containing the chloride ion].

(i) 2HCl⇌>500°CH2+Cl22\text{HCl} \xrightleftharpoons{\gt 500 \degree\text{C}} \text{H}_\text{2} + \text{Cl}_\text{2}2HCl>500°CH2+Cl2(ii) NH4Cl→ΔNH3+HCl\text{NH}_4\text{Cl} \xrightarrow{\Delta} \text{NH}_3 + \text{HCl}NH4ClΔNH3+HCl

Question 1

Question 10Give a balanced equation for thermal dissociation of(i) a gas(ii) a solid [both containing the chloride ion].

Accepted Answer

(i) 2HCl⇌>500°CH2+Cl22	ext{HCl} \xrightleftharpoons{\gt 500 \degree	ext{C}} 	ext{H}_	ext{2} + 	ext{Cl}_	ext{2}2HCl>500°C​H2​+Cl2​(ii) NH4Cl→ΔNH3+HCl	ext{NH}_4	ext{Cl} \xrightarrow{\Delta} 	ext{NH}_3 + 	ext{HCl}NH4​ClΔ​NH3​+HCl

Question 2

Question 16Name the ions obtained when HCl dissociates in aqueous solution.

Accepted Answer

The ions obtained are hydronium ions (H3O+) and chloride ions (Cl-)HCl + H2O ⟶ H3O+ + Cl-

Question 3

Question 17Name the ion responsible for acidic nature of HCl acid.

Accepted Answer

The presence of hydrogen ions [H+] in HCl imparts acidic properties to an aqueous solution of hydrochloric acid.

Question 4

Question 19Give four different word equations relating to acidic properties of an aq. soln. of HCl gas.

Accepted Answer

Magnesium + Hydrochloric acid ⟶ Magnesium chloride + HydrogenCopper oxide + Hydrochloric acid ⟶ Copper chloride + WaterSodium carbonate + Hydrochloric acid ⟶ Sodium chloride + Water + Carbon dioxide gasMagnesium sulphite + Hydrochloric acid ⟶ Magnesium chloride + Water + sulphur dioxide gas

Question 5

Question 20Give balanced equations to obtain(i) H2(ii) CO2(iii) SO2(iv) H2Sfrom dil. HCl.

Accepted Answer

(i) Mg + 2HCl ⟶ MgCl2 + H2(ii) NaHCO3 + HCl ⟶ NaCl + H2O + CO2 [g](iii) Na2SO3 + 2HCl ⟶ 2NaCl + H2O + SO2 [g](iv) FeS + 2HCl ⟶ FeCl2 + H2S

Question 6

Question 25State why aqua regia dissolves gold, which is insoluble in all other acids.

Accepted Answer

Aqua regia : 1 part of conc. HNO3 and 3 parts of conc. HClNitric acid present in aqua regia oxidizes HCl to chlorine.HNO3 + 3HCl ⟶ NOCl + 2H2O + 2[Cl] [nascent chlorine]This nascent chlorine reacts with noble metals like gold forming the corresponding soluble chloride.Au + 3[Cl] ⟶ AuCl3 [Gold (III) Chloride]Hence, aqua regia dissolves noble metals like gold and platinum which are insoluble in all other acids.

Question 7

Question 26Give three tests for hydrochloric acid. Convert silver nitrate to a soluble salt of silver using hydrochloric acid and an alkali.

Accepted Answer

(i) When glass rod dipped in ammonia solution (NH4OH) is brought near vapours of hydrochloric acid, dense white fumes of ammonium chloride are formed.NH3[aq.]+HCl[vapour]⟶NH4Cl[dense white fumes]\underset{	ext{[aq.]}}{	ext{NH}_3} + \underset{	ext{[vapour]}}{	ext{HCl}} \longrightarrow \underset{	ext{[dense white fumes]}}{	ext{NH}_4	ext{Cl}}[aq.]NH3​​+[vapour]HCl​⟶[dense white fumes]NH4​Cl​(ii) On addition of silver nitrate soln. to dil. HCl (acidified with dil. HNO3), curdy white precipitate of silver chloride is obtained.AgNO3 + HCl ⟶ AgCl ↓ + HNO3(iii) On heating a mixture of manganese dioxide and conc. HCl, Greenish yellow gas (chlorine) is evolved.MnO2 + 4HCl ⟶ MnCl2 ↓ + 2H2O + Cl2

Question 8

Question 27State two industrial products manufactured from hydrochloric acid, which are also manufactured from nitric and sulphuric acid. Give two general uses of hydrochloric acid.

Accepted Answer

Industrial products manufactured from HCl acid are :DyesPaintGeneral uses of hydrochloric acid are :Hydrochloric acid dissolves the calcium phosphate present in bones. Hence, it is used in the extraction of glue from bones.Hydrochloric acid dissolves the metallic oxide coating [impurities] on the surface of the metal, thereby cleans the surface. Hence, it is used in pickling of metals before galvanizing.

Question 9

Question 1Hydrogen ChlorideComplete and balance the equationsa. Preparation of hydrogen chloride 1. By direct combinationH2 + Cl2 ⟶ ...............2. Laboratory preparations [metal chloride]NaCl+H2SO4→<200°C...............+HCl ext{NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\lt 200 \degree ext{C}} ............... + ext{HCl}NaCl+H2SO4<200°C...............+HCl NaCl+NaHSO4→>200°C...............+HCl ext{NaCl} + ext{NaHSO}_4 \xrightarrow{\gt 200 \degree ext{C}} ............... + ext{HCl}NaCl+NaHSO4>200°C...............+HCl NaCl+H2SO4→>200°C...............+HCl ext{NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\gt 200 \degree ext{C}} ............... + ext{HCl}NaCl+H2SO4>200°C...............+HCl

Accepted Answer

Hydrogen ChlorideComplete and balance the equationsa. Preparation of hydrogen chloride 1. By direct combinationH2 + Cl2 ⟶ 2HCl2. Laboratory preparations [metal chloride]NaCl+H2SO4→<200°CNaHSO4+HCl ext{NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\lt 200 \degree ext{C}} \bold{NaHSO}_\bold{4} + ext{HCl}NaCl+H2SO4<200°CNaHSO4+HCl NaCl+NaHSO4→>200°CNa2SO4+HCl ext{NaCl} + ext{NaHSO}_4 \xrightarrow{\gt 200 \degree ext{C}} \bold{Na}_\bold{2}\bold{SO}_\bold{4} + ext{HCl}NaCl+NaHSO4>200°CNa2SO4+HCl 2NaCl+H2SO4→>200°CNa2SO4+2HCl2 ext{NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\gt 200 \degree ext{C}} \bold{Na}_\bold{2}\bold{SO}_\bold{4} + ext{2HCl}2NaCl+H2SO4>200°CNa2SO4+2HCl

Question 10

Question 2b. Properties of hydrogen chloride   3. Thermal dissociation2HCl ⇌>500°C ...............+...............2	ext{HCl } \xrightleftharpoons{\gt 500 \degree	ext{C }} ............... + ...............2HCl >500°C ​...............+...............4. Reaction with ammoniaNH3 + HCl ⟶ ...............Hydrocloric acid [dilute]   5. Monobasic acidHCl⇌H2O...............+Cl−	ext{HCl} \xrightleftharpoons{	ext{H}_2	ext{O}} ............... + 	ext{Cl}^{-}HClH2​O​...............+Cl− ;[H+ + H2O ⟶ ...............]Reaction with6. Active metalAl + HCl ⟶ ............... + ...............7. Base - copper [II] oxide- ammonium hydroxideCuO + HCl ⟶ ............... + ...............NH4OH + HCl ⟶ ............... + ...............8. Sodium carbonateNa2CO3 + HCl ⟶ ............... + H2O + ...............9. Sodium hydrogen carbonateNaHCO3 + HCl ⟶ ............... + H2O + ...............10. Sodium sulphiteNa2SO3 + HCl ⟶ ............... + H2O + ...............11. Sodium bisulphiteNaHSO3 + HCl ⟶ ............... + H2O + ...............12. Iron [II] sulphideFeS + HCl ⟶ ............... + ...............13. Silver nitrateAgNO3 + HCl ⟶ ............... + ...............14. Lead nitratePb(NO3)2 + HCl ⟶ ............... + ...............15. Sodium thiosulphate soln.Na2S2O3 + HCl ⟶ ............... + ............... + ............... + ...............Oxidising agents16. Lead dioxide [lead [IV] oxide]PbO2 + HCl ⟶ ............... + H2O + ...............17. Red lead [trilead tetroxide]Pb3O4 + HCl ⟶ ............... + H2O + ...............18. Potassium permanganateKMnO4 + ............... ⟶ ............... + ............... + ............... + Cl219. Potassium dichromateK2Cr2O7+...............→Δ...............+...............+...............+Cl2	ext{K}_2	ext{Cr}_2	ext{O}_7 + ............... \xrightarrow{\Delta} ............... + ............... + ............... + 	ext{Cl}_2K2​Cr2​O7​+...............Δ​...............+...............+...............+Cl2​20. Nitric acid [conc.]HNO3 + 3HCl ⟶ ............... + ............... + Cl2[Au + [Cl] ⟶ ............... ]

Accepted Answer

b. Properties of hydrogen chloride   3. Thermal dissociation2HCl⇌>500°CH2+Cl22	ext{HCl} \xrightleftharpoons{\gt 500 \degree	ext{C}} \bold{H}_\bold{2} + \bold{Cl}_\bold{2}2HCl>500°C​H2​+Cl2​4. Reaction with ammoniaNH3 + HCl ⟶ NH4ClHydrocloric acid [dilute]5. Monobasic acidHCl⇌H2OH++Cl−	ext{HCl} \xrightleftharpoons {	ext{H}_2	ext{O}} \bold{H}^{+} + 	ext{Cl}^{-}HClH2​O​H++Cl− ;[H+ + H2O ⟶ H3O+ ]Reaction with6. Active metal2Al + 6HCl ⟶ 2AlCl3 + 3H27. Base - copper [II] oxide- ammonium hydroxideCuO + 2HCl ⟶ CuCl2 + H2ONH4OH + HCl ⟶ NH4Cl + H2O8. Sodium carbonateNa2CO3 + 2HCl ⟶2NaCl + H2O + CO29. Sodium hydrogen carbonateNaHCO3 + HCl ⟶ NaCl + H2O + CO210. Sodium sulphiteNa2SO3 + 2HCl ⟶ 2NaCl + H2O + SO211. Sodium bisulphiteNaHSO3 + HCl ⟶ NaCl + H2O + SO212. Iron [II] sulphideFeS + 2HCl ⟶ FeCl2 + H2S13. Silver nitrateAgNO3 + HCl ⟶ AgCl + HNO314. Lead nitratePb(NO3)2 + 2HCl ⟶ PbCl2 + 2HNO315. Sodium thiosulphate soln.Na2S2O3 + 2HCl ⟶ 2NaCl + SO2 + S + H2OOxidising agents16. Lead dioxide [lead [IV] oxide]PbO2 + 4HCl ⟶ PbCl2 + 2H2O + Cl217. Red lead [trilead teroxide]Pb3O4 + 8HCl ⟶ 3PbCl2 + 4H2O + Cl218. Pottasium permaganate2KMnO4 + 16HCl ⟶ 2KCl + 2MnCl2 + 8H2O + 5Cl219. Pottasium dichromateK2Cr2O7+14HCl→Δ2KCl+2CrCl3+7H2O+3Cl2	ext{K}_2	ext{Cr}_2	ext{O}_7 + \bold{14HCl} \xrightarrow{\Delta} \bold{2KCl} + \bold{2CrCl}_\bold{3} +\bold{7H}_\bold{2}\bold{O} + 	ext{3Cl}_2K2​Cr2​O7​+14HClΔ​2KCl+2CrCl3​+7H2​O+3Cl2​20. Nitric acid [conc.]HNO3 + 3HCl ⟶ NOCl + 2H2O + 2[Cl][Au + 3[Cl] ⟶ AuCl3 ]

Question 11

Question 6Study the flow chart and give balanced equations with conditions for the conversions A, B, C, D and E

Accepted Answer

The balanced chemical reactions are:A : NaCl+H2SO4→<200°CNaHSO4+HCl [g]	ext{NaCl} + 	ext{H}_2	ext{SO}_4 \xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_4 + 	ext{HCl [g]}NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑B : Zn+2HCl ( dil.)→ΔZnCl2+H2	ext{Zn} + 2	ext{HCl ( dil.)} \xrightarrow{\Delta} 	ext{ZnCl}_2 + 	ext{H}_2Zn+2HCl ( dil.)Δ​ZnCl2​+H2​ ↑C : AgNO3 + HCl ⟶ AgCl (white ppt.) + HNO3D : MnO2+4HClConc.→ΔMnCl2+2H2O+Cl2	ext{MnO}_2 + \underset{	ext{Conc.}}{	ext{4HCl}} \xrightarrow{\Delta} 	ext{MnCl}_2 + 2	ext{H}_2	ext{O} + 	ext{Cl}_2MnO2​+Conc.4HCl​Δ​MnCl2​+2H2​O+Cl2​ ↑E : NaHCO3 + HCl ⟶ NaCl + H2O + CO2 ↑

Question 12

Question 7In the laboratory preparation of hydrochloric acid, hydrogen chloride gas is dissolved in water.(a) Draw a diagram to show the arrangement used for the absorption of HCl gas in water.(b) State why such an arrangement is necessary. Give two reasons for the same.(c) Write balanced chemical equations for the laboratory preparation of HCl gas when the reaction is :    (A) below 200°C    (B) above 200°C

Accepted Answer

(a) Below diagrams show the special funnel arrangement used for the absorption of HCl gas in water:(b) The reasons are :Prevents or minimizes back-suction of water.Provides a large surface area for the absorption of the HCl gas.(c) The equations are:(A) NaCl+H2SO4→<200°CNaHSO4+HCl [g] ext{NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\lt 200 \degree ext{C}} ext{NaHSO}_4 + ext{HCl [g]}NaCl+H2SO4<200°CNaHSO4+HCl [g] ↑(B) 2NaCl+H2SO4→>200°CNa2SO4+2HCl [g] ext{2NaCl} + ext{H}_2 ext{SO}_4 \xrightarrow{\gt 200 \degree ext{C}} ext{Na}_2 ext{SO}_4 + ext{2HCl [g}]2NaCl+H2SO4>200°CNa2SO4+2HCl [g] ↑

Question 13

Question 9Refer to the diagram given below and write balanced equations with conditions, if any, for the following conversions P to S.

Accepted Answer

P — NaCl+H2SO4→<200°CNaHSO4+HCl [g]	ext{NaCl} + 	ext{H}_2	ext{SO}_4 \xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_4 + 	ext{HCl [g]}NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑Q — Fe + 2HCl (dil.) ⟶ FeCl2 + H2 [g]R — NH4OH + HCl (dil.)⟶ NH4Cl + H2OS — PbO2+4HCl→ΔPbCl2+2H2O+Cl2	ext{PbO}_2 + 4	ext{HCl} \xrightarrow{\Delta} 	ext{PbCl}_2 + 2	ext{H}_2	ext{O} + 	ext{Cl}_2PbO2​+4HClΔ​PbCl2​+2H2​O+Cl2​ ↑

Question 14

Question 12The following questions pertain to the laboratory preparation of hydrogen chloride gas:(a) Write the equation for it's preparation mentioning the conditions required.(b) Name the drying agent used in the above preparation and give a reason for the choice.(c) State a safety precaution taken during the preparation of hydrochloric acid.

Accepted Answer

(a) The equation for the laboratory preparation of hydrogen chloride gas :NaCl+H2SO4→<200°CNaHSO4+HCl [g]	ext{NaCl} + 	ext{H}_2	ext{SO}_4 \xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_4 + 	ext{HCl [g]}NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑(b) Concentrated sulphuric acid is used as the drying agent used in the above preparation.Reason — Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent. Other drying agents like phosphorous pentoxide (P2O5) and quick lime (CaO) cannot be used since they react with hydrogen chloride gas.(c) Temperature is maintained at nearly 200°C as at higher temperatures above 200°C the glass apparatus may crack, fuel is wasted, sodium sulphate formed, forms a hard crust which sticks to the glass and is difficult to remove.

Question 15

Question 5Assertion (A): HCl is produced by the reaction of hydrogen and chlorine in diffused sunlight.Reason (R): This reaction is explosive in sunlight.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.Explanation— HCl is produced, when moist hydrogen gas combines with chlorine in presence of diffused sunlight. Hence, assertion (A) is true.H2+Cl2→sunlightdiffused2HCl{	ext{H}_2} + {	ext{Cl}_2} \xrightarrow[	ext{sunlight}]{	ext{diffused}} {2	ext{HCl}}H2​+Cl2​diffusedsunlight​2HClThe formation HCl is a explosive reaction in direct sunlight but it is negligible in dark. So, it is carried out in diffused sunlight. Hence, reason (R) is true.Therefore, Reason (R) thus provides a valid explanation for why this reaction is occurring in diffused sunlight. Hence, Reason (R) is the correct explanation of assertion

Question 16

Question 8Assertion (A): HCl gas fumes in moist air.Reason (R): HCl gas is highly soluble.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.Explanation— Hydrogen chloride (HCl) gas fumes in moist air because it is highly soluble in water. In the presence of moisture, HCl gas dissolves in water vapour in the air to form tiny droplets of hydrochloric acid, which appear as white fumes. So, both the assertion and the reason are true, and the reason correctly explains the assertion.

Question 17

Question 4How will the action of dilute hydrochloric acid enable you to distinguish between the following?(a) Sodium carbonate and sodium sulphite(b) Sodium thiosulphate and sodium sulphite.

Accepted Answer

(a) 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 ↑(b) When sodium thiosulphate is treated with dil. HCl it produces sulphur dioxide gas and yellow sulphur precipitates.Na2S2O3 + 2HCl ⟶ 2NaCl + S + H2O + SO2 ↑However, S is not produced when sodium sulphite is treated with dil.HCl.Na2SO3 + 2HCl ⟶ 2NaCl + H2O + SO2 ↑

Question 18

Question 11Give balanced equations with conditions, if any, for the following conversions(a) Sodium Chloride ⟶ Hydrogen Chloride(b) Hydrogen Chloride ⟶ Iron (II) chloride(c) Hydrogen Chloride ⟶ Ammonium chloride(d) Hydrogen Chloride ⟶ Lead chloride.

Accepted Answer

(a) NaCl+H2SO4→<200°CNaHSO4+HCl [g]	ext{NaCl} + 	ext{H}_2	ext{SO}_4 \xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_4 + 	ext{HCl [g]}NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑(b) Fe + 2HCl (dil.) ⟶ FeCl2 + H2 [g](c) NH4OH + HCl (dil.)⟶ NH4Cl + H2O(d) PbO2+4HCl→ΔPbCl2+2H2O+Cl2	ext{PbO}_2 + 4	ext{HCl} \xrightarrow{\Delta} 	ext{PbCl}_2 + 2	ext{H}_2	ext{O} + 	ext{Cl}_2PbO2​+4HClΔ​PbCl2​+2H2​O+Cl2​ ↑

Question 19

Question 3Identify the gas evolved when :(i) Potassium sulphite is treated with dilute hydrochloric acid.(ii) Concentrated hydrochloric acid is made to react with manganese dioxide.

Accepted Answer

(i) Sulphur dioxide gas(ii) Chlorine gasMnO2+4HCl→ΔMnCl2+2H2O+Cl2	ext{MnO}_2 + 4	ext{HCl} \xrightarrow{\Delta} 	ext{MnCl}_2 + 2	ext{H}_2	ext{O} + 	ext{Cl}_2MnO2​+4HClΔ​MnCl2​+2H2​O+Cl2​ ↑

Question 20

Question 3(2010)(i) State the salt and the acid, used in the laboratory preparation of hydrogen chloride.(ii) Give the equation for the preparation.(iii) State a method to prove that the gas jar used for collection of HCl gas is filled with hydrogen chloride.(iv) Observing the method of collection of the gas, state what you can tell about the density of hydrogen chloride.

Accepted Answer

(i) Salt — Sodium Chloride [NaCl], Acid — Sulphuric acid [H2SO4](ii) NaCl+H2SO4→<200°CNaHSO4+HCl	ext{NaCl} + 	ext{H}_2	ext{SO}_4 \xrightarrow{\lt 200 \degree	ext{C}} 	ext{NaHSO}_	ext{4} + 	ext{HCl}NaCl+H2​SO4​<200°C​NaHSO4​+HCl(iii) A glass rod dipped in NH4OH soln. is brought near the mouth of the gas jar 'Y'. If the gas jar is full with HCl gas then dense white fumes of ammonium chloride are formed.NH3[aq.]+HCl[vapour]⟶NH4Cl[dense white fumes]\underset{	ext{[aq.]}}{	ext{NH}_3} + \underset{	ext{[vapour]}}{	ext{HCl}} \longrightarrow \underset{	ext{[dense white fumes]}}{	ext{NH}_4	ext{Cl}}[aq.]NH3​​+[vapour]HCl​⟶[dense white fumes]NH4​Cl​(iv) This method indicates that HCl gas is heavier than air.

Study of Compounds — Hydrogen Chloride

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