When nitric acid is added to egg shell, it dissolves egg shell. Egg shell is composed of calcium carbonate which dissolves in nitric acid. The reaction between nitric acid and calcium carbonate yields calcium nitrate and carbon dioxide gas. 

CaCO₃ + HNO₃ → Ca(NO₃)₂ + CO₂ + H₂O

The student can use other indicator; like phenolphthalein or methyl orange to check the acidity or alkalinity of a particular solution. The student can also use turmeric powder to check the solutions. It is mentioned that litmus paper is not available. So, we can assume that the laboratory may have other indicators.

When baking powder is heated, carbon dioxide is produced. This can be shown by following equation.

2NaHCO₃ +  Heat → Na₂CO₃ + CO₂ + H₂O 

Evolution of carbon dioxide can be confirmed by passing the gas into lime water. if lime water turns milky, it indicates evolution of carbon dioxide gas. This reaction does not happen when washing soda is heated.

Salt A is sodium hydrogen carbonate (baking soda). When it is heated, it turns into sodium carbonate; which is salt B. In this reaction, carbon dioxide gas is also produced; which is the gas C.

2NaHCO₃ +  Heat → Na₂CO₃ + CO₂ + H₂O 

Sodium hydrogen carbonate is used in bakery products. Sodium carbonate is used for removing hardness of water.

Sodium chloride is subjected to chloralkali process to manufacture sodium hydroxide. Chlorine and hydrogen gas are formed during this process.

2NaCl + 2H₂O → 2NaOH +Cl₂ +H₂

Chlorine reacts with lime water to give bleaching powder.

Ca(OH)₂ + Cl₂ → CaOCl₂ +H₂O 

X is chlorine. Y is bleaching powder.

ANS

Acids which get completely ionized in aqueous solution are called strong acids, e.g. hydrochloric acid, nitric acid and sulphuric acid. Acids which do not get completely ionized in aqueous solution are called weak acids, e.g. acetic acid, citric acid, and formic acid.

Following reaction takes place when zinc is treated with a dilute solution of a strong acid.

Zn +H₂SO₄→ ZnSO₄ + H₂ 

In this reaction, hydrogen gas is produced; which is utilized in the hydrogenation of oil. When a burning matchstick is brought near hydrogen gas, the matchstick burns with a pop sound. This confirms the evolution of hydrogen gas.