Class 10 - Chapter 7A Study of Compounds — Hydrogen Chloride Dalal Simplified ICSE Chemistry Solutions -

Equations Worksheet

Question 1

Hydrogen Chloride	Complete and balance the equations
a. Preparation of hydrogen chloride
1. By direct combination	H₂ + Cl₂ ⟶ ……………
2. Laboratory preparations [metal chloride]	$NaCl + H_{2} SO_{4} < 200° C$

$\dots\dots\dots\dots\dots + HCl$
	$NaCl + NaHSO_{4} > 200° C$

$\dots\dots\dots\dots\dots + HCl$
	$NaCl + H_{2} SO_{4} > 200° C$

\dots\dots\dots\dots\dots + HCl

Answer

Hydrogen Chloride	Complete and balance the equations
a. Preparation of hydrogen chloride
1. By direct combination	H₂ + Cl₂ ⟶ *2HCl*
2. Laboratory preparations [metal chloride]	$NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl$
	$NaCl + NaHSO_{4} > 200° C$

$Na_{2} SO_{4} + HCl$
	$2 NaCl + H_{2} SO_{4} > 200° C$

$Na_{2} SO_{4} + 2HCl$

Question 2

b. Properties of hydrogen chloride
3. Thermal dissociation	$2 HCl > 500° C$

$\dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots$
4. Reaction with ammonia	NH₃ + HCl ⟶ ……………
Hydrocloric acid [dilute]
5. Monobasic acid	$HCl H^{2} O$

$\dots\dots\dots\dots\dots + Cl^{-}$ ; [H⁺ + H₂O ⟶ ……………]
Reaction with
6. Active metal	Al + HCl ⟶ …………… + ……………
7. Base – copper [II] oxide – ammonium hydroxide	CuO + HCl ⟶ …………… + …………… NH₄OH + HCl ⟶ …………… + ……………
8. Sodium carbonate	Na₂CO₃ + HCl ⟶ …………… + H₂O + ……………
9. Sodium hydrogen carbonate	NaHCO₃ + HCl ⟶ …………… + H₂O + ……………
10. Sodium sulphite	Na₂SO₃ + HCl ⟶ …………… + H₂O + ……………
11. Sodium bisulphite	NaHSO₃ + HCl ⟶ …………… + H₂O + ……………
12. Iron [II] sulphide	FeS + HCl ⟶ …………… + ……………
13. Silver nitrate	AgNO₃ + HCl ⟶ …………… + ……………
14. Lead nitrate	Pb(NO₃)₂ + HCl ⟶ …………… + ……………
15. Sodium thiosulphate soln.	Na₂S₂O₃ + HCl ⟶ …………… + …………… + …………… + ……………
Oxidising agents
16. Lead dioxide [lead [IV] oxide]	PbO₂ + HCl ⟶ …………… + H₂O + ……………
17. Red lead [trilead tetroxide]	Pb₃O₄ + HCl ⟶ …………… + H₂O + ……………
18. Potassium permanganate	KMnO₄ + …………… ⟶ …………… + …………… + …………… + Cl₂
19. Potassium dichromate	$K_{2} Cr_{2} O_{7} + \dots\dots\dots\dots\dots Δ$

$\dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots + Cl_{2}$
20. Nitric acid [conc.]	HNO₃ + 3HCl ⟶ …………… + …………… + Cl₂ [Au + [Cl] ⟶ …………… ]

Answer

b. Properties of hydrogen chloride
3. Thermal dissociation	$2 HCl > 500° C$

$H_{2} + Cl_{2}$
4. Reaction with ammonia	NH₃ + HCl ⟶ *NH₄Cl*
Hydrocloric acid [dilute]
5. Monobasic acid	$HCl H^{2} O$

$H^{+} + Cl^{-}$ ; [H⁺ + H₂O ⟶ *H₃O⁺* ]
Reaction with
6. Active metal	2Al + 6HCl ⟶ *2AlCl₃* + *3H₂*
7. Base – copper [II] oxide – ammonium hydroxide	CuO + 2HCl ⟶ *CuCl₂* + *H₂O* NH₄OH + HCl ⟶ *NH₄Cl* + *H₂O*
8. Sodium carbonate	Na₂CO₃ + 2HCl ⟶*2NaCl* + H₂O + *CO₂*
9. Sodium hydrogen carbonate	NaHCO₃ + HCl ⟶ *NaCl* + H₂O + *CO₂*
10. Sodium sulphite	Na₂SO₃ + 2HCl ⟶ *2NaCl* + H₂O + *SO₂*
11. Sodium bisulphite	NaHSO₃ + HCl ⟶ *NaCl* + H₂O + *SO₂*
12. Iron [II] sulphide	FeS + 2HCl ⟶ *FeCl₂* + *H₂S*
13. Silver nitrate	AgNO₃ + HCl ⟶ *AgCl* + *HNO₃*
14. Lead nitrate	Pb(NO₃)₂ + 2HCl ⟶ *PbCl₂* + *2HNO₃*
15. Sodium thiosulphate soln.	Na₂S₂O₃ + 2HCl ⟶ *2NaCl* + *SO₂* + S + *H₂O*
Oxidising agents
16. Lead dioxide [lead [IV] oxide]	PbO₂ + 4HCl ⟶ *PbCl₂* + 2H₂O + *Cl₂*
17. Red lead [trilead teroxide]	Pb₃O₄ + 8HCl ⟶ *3PbCl₂* + 4H₂O + *Cl₂*
18. Pottasium permaganate	2KMnO₄ + *16HCl* ⟶ *2KCl* + *2MnCl₂* + *8H₂O* + 5Cl₂
19. Pottasium dichromate	$K_{2} Cr_{2} O_{7} + 14HCl Δ$

$2KCl + 2CrCl_{3} + 7H_{2} O + 3Cl_{2}$
20. Nitric acid [conc.]	HNO₃ + 3HCl ⟶ *NOCl* + *2H₂O* + 2[Cl] [Au + 3[Cl] ⟶ *AuCl₃* ]

Question 3

Tests for hydrochloric acid
21. Glass rod dipped in ammonia soln.	NH₃ + …………… ⟶ ……………
22. Addition of silver nitrate soln.	AgNO₃ + …………… ⟶ …………… ↓ + ……………
23. Solubility of silver chloride	AgCl + NH₄OH ⟶ …………… + ……………
24. Heated with manganese dioxide [manganese [IV] oxide]	…………… + HCl ⟶ MnCl₂ + …………… + …………… [g]

Answer

Tests for hydrochloric acid
21. Glass rod dipped in ammonia soln.	NH₃ + *HCl* ⟶ *NH₄Cl*
22. Addition of silver nitrate soln.	AgNO₃ + *HCl* ⟶ *AgCl* ↓ + *HNO₃*
23. Solubility of silver chloride	AgCl + 2NH₄OH ⟶ *[Ag(NH₃)₂Cl)]* + *2H₂O*
24. Heated with manganese dioxide [manganese [IV] oxide]	*MnO₂* + 4HCl ⟶ MnCl₂ + *2H₂O* + *Cl₂* [g]

Questions

Question 1(2007)

Write a balanced equation for Sodium chloride from sodium carbonate soln. and dilute hydrochloric acid.

Answer

Na₂CO₃ + 2HCl [dil.] ⟶ 2NaCl + H₂O + CO₂ [g.]

Question 2(2007)

Of the two gases, NH₃ and HCl, which is more dense. Name the method of collection of this gas.

Answer

Hydrogen chloride gas is denser than NH₃.
Reason — V.D. of NH₃ = 8.5 and that of HCl = 18.25

HCl gas is collected by upward displacement of air.

Question 3(2007)

Give one example of a reaction between the above two gases which produces a solid.

Answer

NH₃ [g] + HCl [g] ⟶ NH₄Cl (s-solid)

When a gas jar containing HCl gas in inverted over a jar full of ammonia gas, dense white fumes are formed. These fumes consist of particles of solid ammonium chloride suspended in air.

Question 4(2007)

Write equations for the reaction of dil. HCl with each of the following :

(i) iron

(ii) sodium hydrogen carbonate

(iii) iron [II] sulphide

(iv) sodium sulphite

Answer

(i) Fe + 2HCl ⟶ FeCl₂ + H₂

(ii) NaHCO₃ + HCl ⟶ NaCl + H₂O + CO₂

(iii) FeS + 2HCl ⟶ FeCl₂ + H₂S

(iv) Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ [g]

Question 1(2008)

What property of hydrogen chloride is demonstrated when it is collected by downward delivery [upward displacement]. Why is hydrogen chloride not collected over water.

Answer

Hydrogen chloride is 1.28 times heavier than air, hence it is collected by downward delivery [upward displacement]. Hydrogen chloride is not collected over water since it is highly soluble in water.

Question 2(2008)

Write equations for the reactions :

(i) dil. HCl and sodium thiosulphate.

(ii) dil. HCl and lead nitrate soln.

Answer

(i) Na₂S₂O₃ + 2HCl ⟶ 2NaCl + SO₂ + S + H₂O

(ii) Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ ↓ + 2HNO₃

Question 1(2009)

Name the gas evolved – The gas produced by the action of concentrated sulphuric acid on sodium chloride.

Answer

Hydrogen chloride (HCl)

$NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl [g]$

Question 2(2009)

Match each substance A to E listed below with the appropriate description given below :

[A] Sulphur
[B] Silver chloride
[C] Hydrogen chloride
[D] Copper [II] Sulphate
[E] Graphite.

(i) A covalent compound which behaves like an ionic compound in aqueous solution.
(ii) A compound which is insoluble in cold water but soluble in excess of ammonia solution.

Answer

(i) [C] Hydrogen chloride
(ii) [B] Silver chloride

Question 3(2009)

Write a balanced equation for each of the following :

(i) Red lead is warmed with concentrated hydrochloric acid.

(ii) Magnesium metal is treated with dilute hydrochloric acid.

Answer

(i) $Pb_{3} O_{4} + 8 HCl Δ$

$3 PbCl_{2} + 4 H_{2} O + Cl_{2}$

(ii) Mg + 2HCl ⟶ MgCl₂ + H₂

Question 4(2009)

Correct the statement:

HCl acid is prepared in the lab. by passing hydrogen chloride directly through water.

Answer

HCl acid is prepared in the lab. by passing hydrogen chloride gas in water using a special funnel arrangement.

Question 1(2010)

Select the correct answer from A, B, C and D.

(i) Aqua regia is a mixture of :

A : Dilute hydrochloric and conc. nitric acid
B : Conc. hydrochloric and dilute nitric acid
C : One part of conc. hydrochloric acid and 3 parts of conc. nitric acid.
D : 3 parts of conc. hydrochloric acid and 1 part of conc. nitric acid

Answer

D : 3 parts of conc. hydrochloric acid and 1 part of conc. nitric acid

Question 2(2010)

State your observation when :
A glass rod dipped in NH₄OH soln. is brought near an open bottle containing conc. HCl

Answer

Dense white fumes of ammonium chloride are formed when a glass rod dipped in NH₄OH soln. is brought near an open bottle containing conc. HCl

$[aq.] NH^{3} + [vapour] HCl ⟶ [dense white fumes] NH^{4} Cl$

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.

Answer

(i) Salt — Sodium Chloride [NaCl], Acid — Sulphuric acid [H₂SO₄]

(ii) $NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl$

(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.

$[aq.] NH^{3} + [vapour] HCl ⟶ [dense white fumes] NH^{4} Cl$

(iv) This method indicates that HCl gas is heavier than air.

Question 4(2010)

How would you distinguish between dilute HCl and dilute HNO₃, by addition of only one solution.

Answer

When silver nitrate soln. is added to dil. HCl, curdy white ppt. of silver chloride is formed. Whereas, there is no reaction when silver nitrate soln. is added to dil. HNO₃.

AgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃

AgNO₃ + HNO₃ ⟶ no reaction

Question 5(2010)

Name two gases which can be used in the study of the fountain experiment. State the common property demonstrated by the fountain experiment ?

Answer

Dry hydrogen chloride gas (HCl) and Ammonia (NH₃) gas can be used in the study of the fountain experiment.

High solubility of HCl gas in water is the common property demonstrated by the fountain experiment.

Question 1(2011)

Choose the correct answer:

Hydrogen chloride gas being highly soluble in water is dried by :

Anhydrous calcium chloride
Phosphorous pentaoxide
Quick lime
Conc. sulphuric acid.

Answer

Concentrated sulphuric acid.

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.

Question 2(2011)

Write balanced equation of dil. HCl with Calcium bicarbonate.

Answer

Ca(HCO₃)₂ + 2HCl ⟶ CaCl₂ + 2H₂O + 2CO₂

Question 3(2011)

In the laboratory preparation of hydrochloric acid, hydrogen chloride gas is dissolved in water.

(i) Draw a diagram to show the arrangement used for the absorption of HCl gas in water.

(ii) State why such an arrangement is necessary? Give two reasons for the same.

(iii) Write balanced chemical equations for the laboratory preparation of HCl gas when the reactants are :

(A) below 200°C

(B) above 200°C

Answer

(i) Below diagrams show the special funnel arrangement used for the absorption of HCl gas in water:

Draw a diagram to show the arrangement used for the absorption of HCl gas in water. Study of Hydrogen Chloride, Simplified Chemistry Dalal Solutions ICSE Class 10.

(ii) The reasons are :

Prevents or minimizes back-suction of water.
Provides a large surface area for the absorption of the HCl gas.

(iii) The equations are:

(A) $NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl [g]$

(B) $2NaCl + H_{2} SO_{4} > 200° C$

$Na_{2} SO_{4} + 2HCl [g]$

Question 1(2012)

Rewrite the correct statement with the missing word/s : Aqua regia contains one part by volume of nitric acid and three parts by volume of hydrochloric acid.

Answer

Aqua regia contains one part by volume of conc. nitric acid and three parts by volume of conc. hydrochloric acid.

Question 2(2012)

Give reason for the following : Hydrogen chloride gas cannot be dried over quick lime.

Answer

Quicklime [CaO] is alkaline in nature and it reacts with HCl forming the respective chloride. Hence, it can’t be used as a drying agent.

Question 3(2012)

Give a balanced equation for the reaction : Conc. hydrochloric acid and potassium permanganate solution.

Answer

$2 KMnO_{4} + 16 HCl Δ$

$2 KCl + 2 MnCl_{2} + 8 H_{2} O + 5 Cl_{2}$

Question 4(2012)

Give balanced equations with conditions, if any, for the following conversions A to D.

A : Sodium Chloride ⟶ Hydrogen Chloride

B : Hydrogen Chloride ⟶ Iron (II) chloride

C : Hydrogen Chloride ⟶ Ammonium chloride

D : Hydrogen Chloride ⟶ Lead chloride.

Answer

A: $NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl [g]$

B: Fe + 2HCl (dil.) ⟶ FeCl₂ + H₂ [g]

C: NH₄OH + HCl (dil.)⟶ NH₄Cl + H₂O

D: $PbO_{2} + 4 HCl Δ$

$PbCl_{2} + 2 H_{2} O + Cl_{2}$

Question 1(2013)

Identify the gas evolved when :

(i) Potassium sulphite is treated with dilute hydrochloric acid.

(ii) Concentrated hydrochloric acid is made to react with manganese dioxide.

Answer

(i) Sulphur dioxide gas

(ii) Chlorine gas
$MnO_{2} + 4 HCl Δ$

$MnCl_{2} + 2 H_{2} O + Cl_{2}$

Question 2(2013)

State one appropriate observation for :

(i) Copper sulphide is treated with dilute hydrochloric acid.

(ii) A few drops of dil. HCl are added to AgNO₃ soln. followed by addition of NH₄OH soln.

Answer

(i) A colourless gas having smell of rotten eggs is given off. The gas evolved is H₂S

CuS + 2HCl ⟶ CuCl₂ + H₂S

(ii) Curdy white precipitate of silver chloride [AgCl] is obtained, which is soluble in excess of NH₄OH.

AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃

AgCl + 2NH₄OH ⟶ [Ag(NH₃)₂Cl)] + 2H₂O

Question 1(2014)

Fill in the blank from the choices in the bracket :

Quicklime is not used to dry HCl gas because …………… [CaO is alkaline, CaO is acidic, CaO is neutral]

Answer

Quicklime is not used to dry HCl gas because CaO is alkaline.

Question 2(2014)

Write the balanced equation for:
Action of dilute hydrochloric acid on sodium sulphide.

Answer

Action of dilute hydrochloric acid on sodium sulphide.

Na₂S + 2HCl ⟶ 2NaCl + H₂S [g.]

Question 3(2014)

State your observation:
Dilute HCl is added to sodium carbonate crystals.

Answer

Na₂CO₃ + 2HCl ⟶ 2NaCl + H₂O + CO₂ ↑

Effervescence of CO₂ seen which turns lime water milky

Question 4(2014)

Study the figure given below and answer the questions that follow :

Study the figure and answer the questions. Identify the gas Y. What property of gas Y does this experiment demonstrate? Name another gas which has the same property and can be demonstrated through this experiment. Study of Hydrogen Chloride, Simplified Chemistry Dalal Solutions ICSE Class 10.

(i) Identify the gas Y.

(ii) What property of gas Y does this experiment demonstrate?

(iii) Name another gas which has the same property and can be demonstrated through this experiment.

Answer

(i) Dry HCl (Hydrogen chloride) gas is the gas Y

(ii) High solubility of HCl in water

(iii) Ammonia (NH₃) gas also demonstrates high solubility in water.

Question 1(2015)

Select from the gases — ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne — The gas which produces dense white fumes with ammonia gas.

Answer

Hydrogen chloride

NH₃ [g] + HCl [g] ⟶ NH₄Cl (s-solid)

When a gas jar containing HCl gas in inverted over a jar full of ammonia gas, dense white fumes are formed. These fumes consists of particles of solid ammonium chloride suspended in air.

Question 2(2015)

Identify the acid which on mixing with AgNO₃ soln. gives a white precipitate, soluble in excess ammonium hydroxide.

Answer

Dilute hydrochloric acid

AgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃

Question 3(2015)

The following questions pertain to the laboratory preparation of hydrogen chloride gas:

(i) Write the equation for it’s preparation mentioning the condition required.

(ii) Name the drying agent used in the above preparation and give a reason for the choice.

(iii) State a safety precaution taken during the preparation of hydrochloric acid.

Answer

(i) The equation for the laboratory preparation of hydrogen chloride gas :

$NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl [g]$

(ii) 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.

(iii) The precautions taken are:

The reaction mixture is initially heated very slowly to control the evolution of HCl gas.
The lower end of the thistle funnel should dip below the acid in the flask otherwise the HCl gas obtained will escape out from the thistle funnel.

Question 1(2016)

Select the correct answer from A, B, C and D : The aim of the Fountain experiment is to prove that :

(A) HCl turns blue litmus red

(B) HCl is denser than air

(D) HCl fumes in moist air.

Answer

Question 2(2016)

Fill in the blank : ……………[AgCl / PbCl₂], a white precipitate is soluble in excess NH₄OH.

Answer

AgCl, a white precipitate is soluble in excess NH₄OH.

Question 3(2016)

Write balanced chemical equation for : Action of hydrochloric acid on sodium bicarbonate.

Answer

NaHCO₃ + HCl ⟶ NaCl + H₂O + CO₂ ↑

Question 4(2016)

State your observations when dilute hydrochloric acid is added to :

(i) Lead nitrate soln. and the mixture is heated.

(ii) Copper carbonate.

(iii) Sodium thiosulphate.

Answer

(i) White precipitate of PbCl₂ is formed which is soluble in hot water.

Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ ↓ + 2HNO₃

(ii) Effervescence of CO₂ seen which turns lime water milky

CuCO₃ + 2HCl ⟶ CuCl₂ + H₂O + CO₂

(iii) Yellow particles of S precipitate.

Na₂S₂O₃ + 2HCl ⟶ 2NaCl + SO₂ + S + H₂O

Question 5(2016)

Identify the gas evolved and give the chemical test when dilute hydrochloric acid reacts with :

(i) Sodium sulphite.

(ii) Iron [II] sulphide.

Answer

(i) SO₂ is evolved when dilute hydrochloric acid reacts with sodium sulphite.

Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ [g]

(ii) H₂S gas is evolved when dilute hydrochloric acid reacts with Iron [II] sulphide.

FeS + 2HCl ⟶ FeCl₂ + H₂S

Question 1(2017)

Fill in the blanks –

Potassium sulphite on reacting with hydrochloric acid, releases …………… gas. [Cl₂, SO₂, H₂S]

Answer

Potassium sulphite on reacting with hydrochloric acid, releases SO₂ gas.

Question 2(2017)

Identify the substance underlined – A solid formed by the reaction of two gases, one of which is acidic and the other basic in nature.

Answer

Ammonium chloride.

NH₃ [g] + HCl [g] ⟶ NH₄Cl (s-solid)

Question 3(2017)

State one relevant observation – Action of dilute hydrochloric acid on iron [II] sulphide.

Answer

H₂S gas is evolved. It has a foul smell like rotten eggs.

FeS + 2HCl [g] ⟶ FeCl₂ + H₂S

Question 4(2017)

Certain blanks spaces are left in the following table as A & B. Identify each of them.

Lab preparation of	Reactants used	Products formed	Drying agent	Method of collection
HCl gas	NaCl + H₂SO₄	A	Conc. H₂SO₄	B

Answer

A : The products are sodium hydrogen sulphate (NaHSO₄) and HCl gas.

B : HCl gas is collected by the upward displacement of air method.

Question 1(2019)

Choose the correct answer from the options A, B, C and D given :

The drying agent used to dry HCl gas is :

A : Conc. H₂SO₄
B : ZnO
C : Al₂O₃
D : CaO

Answer

Conc. H₂SO₄

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.

Question 2(2019)

Fill in the blanks with the choices given in the bracket:

When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the products formed is …………… [sodium hydrogen sulphate / sodium sulphate / chlorine]

Answer

When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the products formed is sodium hydrogen sulphate

Question 3(2019)

State one observation for the following:

A small piece of zinc is added to dilute hydrochloric acid.

Answer

Effervescence of H₂ gas can be seen.

Zn + 2HCl ⟶ ZnCl₂ + H₂

Question 1(2020)

State one relevant reason for:
Hydrogen chloride gas fumes in moist air.

Answer

Due to its high solubility, HCl gas fumes in moist air and forms a mist of droplets of HCl acid.

Question 2(2020)

Complete the following by selecting the correct option from the choices given.

(i) The indicator which does not change colour on passage of HCl gas is ………….. [methyl orange, moist blue litmus, phenolphthalein].

(ii) The acid which cannot act as an oxidizing agent is …………… [conc. H₂SO₄, conc. HNO₃, conc. HCl]

Answer

(i) The indicator which does not change colour on passage of HCl gas is phenolphthalein.

(ii) The acid which cannot act as an oxidizing agent is conc. HCl

Question 3(2020)

Hydrogen chloride gas is prepared in the laboratory using conc. H₂SO₄ and NaCl. Answer the questions that follow based on this reaction.

(i) Give the balanced chemical equation for the reaction with suitable condition[s] if any.

(ii) Why is concentrated sulphuric acid used instead of conc. nitric acid.

(iii) How is the gas collected.

(iv) Name the drying agent not used for drying the gas.

Answer

(i) Balanced chemical equation for the reaction are :

$NaCl + H_{2} SO_{4} < 200° C$

$NaHSO_{4} + HCl [g.]$

(ii) As conc. H₂SO₄ is non-volatile and has a high boiling point, therefore, it displaces the volatile hydrogen chloride from the salt sodium chloride. Hence, conc. H₂SO₄ is used as a reactant in the laboratory preparation of HCl from sodium chloride.
Conc. nitric acid cannot be used in place of conc. H₂SO₄ since it is volatile and may volatize out along with the hydrogen chloride.

(iii) The gas is collected by upward displacement of air method.

(iv) Quicklime (CaO) and phosphorous pentoxide [P₂O₅] are not used as drying agent, since they react with HCl forming their respective chlorides