Question

Q. (i) Nitya took two test tubes A and B. In test tube A she put 10 mL of dilute NaOH and in test tube B she put 10 mL of dilute HCI. Write the changes observed in both the test tubes on adding a pinch of sodium carbonate and also write the chemical reaction involved.
(ii) Give any two examples of olfactory indicators​

Answer 1

Given:

Nitya took two test tubes A and B. In test tube A she put 10 mL of dilute NaOH and in test tube B she put 10 mL of dilute HCl.

To find:

Changes observed in both the test tubes after adding a pinch of sodium carbonate.

Solution:

Test Tube A:

Na2CO3 (Sodium Carbonate) is a salt of weak acid and strong base. Hence , in aqueous solutions , it behaves like a base due to presence of excess OH- ions.

After addition of sodium carbonate to this test tube, no such changes are observed.

This is because , one base doesn't react with another base.

Test Tube B:

After addition of sodium carbonate to this test tube, rising bubbles are observed in the solution due to release of carbon dioxide.

The reaction between hydrochloric acid and sodium carbonate goes as follows :

$\boxed{\sf{2HCl + Na_{2}CO_{3} \rightarrow 2NaCl + H_{2}O + CO_{2}(\uparrow)}}$

Examples of Olfactory Indicators :

• Onion

• Clove oil

• Vanilla