Question

Which of the four test tubes containing the following chemicals shows the brisk

effervesence while dilute acetic acid was adde​

Answer 1

Explanation:

Brisk effervescence will be observed in test tubes 2 and 3.

This is because an acid reacts with metal carbonate and metal bicarbonate to evolve Carbon-dioxide gas with brisk effervescence.

The reactions involved are-

Test tube 2:-

CH3COOH (aq) + NaHCO3 (aq) ------->

CH3COONa (aq) H2O + CO2 (g)

Test tube 3 -

2CH3COOH (aq) + K2CO3 -------->

2CH3COOK (aq) + CO2 (g) + H2O

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Answer 2

Complete Question:

Which of the four test tubes containing the following chemicals shows the brisk  effervescence while dilute acetic acid was adde​d to it:

i) KOH ii) NaHCO​3 iii) K2CO3 iv) NaCl

Solution:

The following test tubes will show brisk  effervescence while

dilute acetic acid was adde​d to it:

(ii) NaHCO​3

(iii) K2CO3

- The brisk effervescence is due to the evolution of CO2.

- When an acid reacts with a metal carbonate, it evolves carbon dioxide gas.

- The reaction in (ii) test tube is:

NaHCO3 + CH3COOH → CH3COONa + CO2 + H2O

- The reaction in (iii) test tube is:

K2CO3 + 2 CH3COOH → 2 CH3COOK + CO2 + H2O

- The test tubes (i) and (iv) have base and metal chloride which do not give CO2 with acetic acid.

- So, the correct answer is test tubes (ii) and (iii).