You are provided with two reagent bottles marked A and B. One of which contains $NH_4OH$ solution and the other contains NaOH solution. How will you identify them by a chemical test?

Home » You are provided with two reagent bottles marked A and B. One of which contains solution and the other contains NaOH solution. How will you identify them by a chemical test?

Analytical Chemistry: Uses of Ammonium Hydroxide and Sodium Hydroxide | Chemistry | Class 10 | ICSE | Selina

You are provided with two reagent bottles marked A and B. One of which contains $NH_4OH$ solution and the other contains NaOH solution. How will you identify them by a chemical test?

Solution:

Calcium salts, such as calcium chloride, can be used to distinguish between reagent bottles A and B Ca(NO₃)₂.

On adding NaOH to Ca(NO₃)₂, a white precipitate Ca (OH)₂ is formed which is sparingly soluble in excess of NaOH.

Ca(NO₃)₂+ 2NaOH → Ca(OH)₂+ 2NaNO₃

In contrast, when $NH_4OH$ is added to calcium salts, no precipitation of $Ca(OH)_2$ is observed, even when an excess of $NH_4OH$ is added. This is because the concentration of $OH^-$ ions formed by the ionization of $NH_4OH$ is so low that it is unable to precipitate the calcium hydroxide.

Thus, the reagent bottle which gives white precipitate is NaOH and the other one should contain NH₄OH.

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