Sudha took lemon in two flask . She put salt in flask 1 and washing soda in flask 2 . She observed lots of bubbles in flask 2 but nothing in flask 1 .what could be the reason for this ?

Dear student,

Lemon juice is acidic in nature and washing soda is slightly basic.

Therefore, in the flask 2, reaction between thr acid and the base takes place to release the carbon dioxide.
$2HA+N{a}_{2}C{O}_3\underset{}{\to }2NaA+H_{2}O+C{O}_2$
Thus the bubbles are seen in the flask 2.

Regards