Question

Question 37.
How would you distinguish between baking powder and washing soda by heating ?

Answer 1

On heating ${\text{NaHCO}}_3$ (baking soda), ${\text{CO}}_2$ (carbon dioxide) gas is given out that turns lime water milky.

$2{\text{NaHCO}}_3\stackrel{\text{Heat}}{\to }{\text{Na}}_2{\text{CO}}_3+{\text{H}}_2\text{O}+{\text{CO}}_2$

While on heating ${\text{Na}}_2{\text{CO}}_3.10{\text{H}}_2\text{O}$ (washing soda) water of crystallisation is given out and the salt becomes anhydrous. The presence of water of crystallisation given as product can be tested by treating it with anhydrous ${\text{CuSO}}_4$ (white) which becomes blue in colour in its contact.

${\text{Na}}_2{\text{CO}}_3.10{\text{H}}_2\text{O}\stackrel{\text{Heat}}{\to }{\text{Na}}_2{\text{CO}}_3+\text{1}0{\text{H}}_2\text{O}$