List of All Important Equations for HCl

Frequently Tested Topics:

  • Laboratory Preparation of Hydrogen Chloride Gas

  • Laboratory Preparation of Hydrochloric Acid

  • Equations and Observations Based on Acidic Property

*Note that other aspects of the chapter are equally important.

Important Past Questions:

  • Write balanced chemical equations for the following reactions:

i) zinc and dilute hydrochloric acid (2006)

ii) calcium carbonate and dil. hydrochloric acid (2006)

iii) sodium chloride from sodium carbonate soln. and dilute hydrochloric acid (2007)

iv) iron and dil. HCl (2007)

v) sodium hydrogen carbonate and dil. HCl (2007, 2016))

vi) iron [II] sulphide and dil. HCl (2007)

vii) sodium sulphite and dil. HCl (2007)

viii) lead nitrate soln. and dil HCl (2008)

ix) magnesium metal is treated with dil. HCl (2009)

x) calcium bicarbonate with dil. HCl

xi) action of dilute hydrochloric acid on sodium sulphide (2014)

xii) action of dilute hydrochloric acid on magnesium sulphite (2018)

  • State a relevant observation for:

i) hydrochloric acid is added to silver nitrate soln. (2006)

ii) a glass rod dipped in NH4OH soln. is brought near an open bottle containing conc. HCl (2010)

iii) copper sulphide is treated with dilute hydrochloric acid (2013)

iv) dilute HCl is added to sodium carbonate crystals (2014)

v) dilute HCl is added to lead nitrate soln. and the mixture is heated (2016, 2018)

vi) dilute HCl is added to copper carbonate (2016)

vii) action of dilute hydrochloric acid on iron [II] sulphide (2017)

  • Name the gas evolved during:

i) the action of conc. sulphuric acid on sodium chloride (2009)

ii) potassium sulphite is treated with dilute hydrochloric acid (2013)

iii) conc. hydrochloric acid is made to react with manganese dioxide (2013)

iv) when dilute hydrochloric acid reacts with sodium sulphite (2016)

v) when dilute hydrochloric acid reacts with iron [II] sulphide (2016)

vi) action of dilute hydrochloric acid on sodium sulphide (2018)

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

i) What property of hydrogen chloride is demonstrated when it is collected by downward delivery (upward displacement)? (2008, 2010)

ii) Why is hydrogen chloride not collected over water? (2008)

iii) Write the equation for its preparation, mentioning the condition required. (2015)

iv) Name the drying agent used in the above preparation and give a reason for the choice. (2015)

v) State a safety precaution taken during the preparation of hydrochloric acid. (2015)

vi) Name the acid used for the preparation of hydrogen chloride gas in the laboratory. State why this particular acid is preferred to other acids. (2018)

vii) Give reason: hydrogen chloride gas cannot be dried over quicklime. (2012, 2014)

viii) State the salt and the acid used in the laboratory preparation of hydrogen chloride. (2010)

ix) Give the equation for the preparation. (2010, 2011, 2018)

x) State a method to prove that the gas jar used for collection of HCl gas is filled with hydrogen chloride. (2010)

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

A: below 200°C       B: above 200°C   (2011)

  • Of the two gases NH3 and HCl, which is more dense? Name the method of collection of this gas. Give one example of a reaction between the above two gases which produces a solid.


  • Identify the substance underlined -

i) a solid formed by the reaction of two gases, one of which is acidic and other basic in nature. (2017)

ii) the acid which on mixing with silver nitrate soln. produces a white precipitate which is soluble in excess ammonium hydroxide. (2015)

  • For the preparation of hydrochloric acid in the laboratory:

i) Draw a diagram to show the arrangement used for the absorption of HCl gas in water. (2011)

ii) State why such an arrangement is necessary. Give two reasons for the same. (2011, 2018)

iii) State why direct absorption of hydrogen chloride gas in water is not feasible. (2018)

iv) Correct the statement - HCl acid is prepared in the lab by passing hydrogen chloride directly through water. (2009)

  • Select the correct answer:

i) Aqua regia is a mixture of :

A] dilute hydrochloric acid and conc. nitric acid

B] conc. hydrochloric acid and dilute nitric acid

C] one part of conc. hydrochloric acid and 3 parts of nitric acid

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


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

A] anhydrous calcium chloride B] phosphorous pentoxide C] quick lime D] conc. sulphuric acid


iii) The aim of the fountain experiment is to prove that:

A] HCl turns blue litmus red

B] HCl is denser than air

C] HCl is highly soluble in water

D] HCl fumes in moist air

(2010, 2014, 2016)

  • Fill in the blanks:

i) ______ (AgCl/PbCl2) , a white precipitate is soulble in excess NH4OH. (2016)

ii) Potassium sulphite on reacting with hydrochloric acid, releases ______ gas. (Cl2, SO2, H2S)  (2017)

iii) Dry hydrogen chloride gas can be collected by _____ displacement of air. (downward/upward)  (2018)

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


  • Rewrite the correct statement with the missing words:

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