Q.Give the tests for carboxylic acid group.

Carboxylic acids are confirmed by two simple chemistry tests: they release carbon dioxide gas from sodium bicarbonate (a test not given by phenols, which are much weaker acids), and they form a fragrant ester on warming with an alcohol in the presence of an acid catalyst.

Test 1 — Sodium bicarbonate test: a small amount of the compound is treated with a solution of sodium bicarbonate ($NaHCO_3$). A carboxylic acid, being sufficiently acidic (unlike phenols, which are much weaker acids and do NOT liberate $CO_2$ from bicarbonate), reacts to give brisk effervescence of carbon dioxide gas, which turns lime water milky: $RCOOH + NaHCO_3 \rightarrow RCOONa + H_2O + CO_2\uparrow$ This test is especially useful to distinguish carboxylic acids from phenols, which give a negative result.

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