Question

Solid sodium chloride is treated with concentrated sulphuric acid in a dry test tube. The gas evolved was tested successively with
A) dry blue litmus paper
B) moistened blue litmus paper
What will you observe in each of the above cases? Give reason for each observation.

Answer 1

On passing through dry blue litmus no change occurs....

But on passing through wet blue litmus , blue litmus paper turns to red ..... This means the gas is acidic.....

Chemical Equation ---

2NaCl + H2SO4 -----> Na2SO4 + 2HCl

This activity shows that hydrogen ions in HCl are produced in the presence of water.... The separation of H+ ion from HCl molecules cannot occur in the absence of water....

Hope it helps

Answer 2

HCl gas is produced.

2NaCl + H2SO4 → Na2SO4 + 2HCl

1.The gas when passed through dry litmus paper will show no change in colour because it cannot show acidic properties as H+ is not present.

2. The gas when passed through moist litmus paper will show colour change to red.

3.It shows acidic properties because H+ ions are produced when HCl dissolves in water.