X CHEMISTRY- ACID,BASE & SALT -Q&A: 2

Q1.            Why do HCl, HNO3, etc. show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Ans: HCl and HNO₃ etc. disintegrate in presence of water to form hydrogen ions (H⁺). since hydrogen ions can’t exist alone they combine with H₂O to form hydronium ions (H₃O⁺). The reaction can be given as follows:

HCl → H⁺ + Cl^–

H⁺ + H₂O → H₃O⁺

Because of this property HCl and HNO₃ show acidic character in aqueous solutions. On the other hand, alcohol and glucose can not disintegrate or dissociate in water to form hydrogen ions. Hence, they do not show acidic character. 

Additional Information: Also these(alcohol and glucose) are not capable of conducting electricity as these don’t produces ions which are essential for conduction of electricity. 

Q2.             Why does an aqueous solution of acid conduct electricity?

Ans: When dissolved in water, acids disintegrate to form ions e.g.,

HCl + H₂O → Cl^– + H₃O⁺   

These ions are responsible for electrical conductivity.

Q3.            Why does dry HCl gas not change the colour of the dry litmus paper?

Ans: We know that the colour of the litmus is changed by H⁺ ions of an acid. Dry HCl does not disintegrate to give H⁺ ions. It is only in the aqueous medium that an acid disintegrate to give ions. Since both HCL and litmus paper don’t contain water the colour of litmus paper does not change.