Question

1.Which one of the following four metals would be displaced from the solution of its salts by other three metals?

(a) Mg

(b) Ag

(c) Zn

(d) Cu


2. 2 mL each of concentrated HCl, HNO3, and a mixture of concentrated HCl and concentrated

HNO3 in the ratio of 3: 1 were taken in test tubes labeled as A, B, and C. A small piece of metal

was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be:

(a) Al

(b) Au

(c) Cu

(d) Pt

Answer 1

Answer:

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1.Which one of the following four metals would be displaced from the solution of its salts by other three metals?

(b) Ag (Silver metal) .

2. 2 mL each of concentrated HCl, HNO3, and a mixture of concentrated HCl and concentrated HNO3 in the ratio of 3: 1 were taken in test tubes labeled as A, B, and C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be:

(b) Au .

Explanation :

As per the given question, the Aqua regia is the given mixture to test the metals in test tubes A, B and C. A mixture of three parts of concentrated hydrochloric acid and one part of concentrated nitric acid(Aqua regia - 3:1 ratio) is capable of dissolving gold.

Gold is a metal that cannot be dissolved in dilute acids and dissolves only in aqua regia.

Hence, the metal in test tube C must be gold (Au).

The correct option is (B).