Question

Insoluble salts can be made using a precipitation reaction. The method can be used to find the formula of a salt. In an experiment, $6.0 {cm}^{3}$ of a solution of the nitrate of metal X was placed in a narrow test tube and $1.0 {cm}^{3}$ of aqueous sodium phosphate, ${Na}_{3} {PO}_{4}$ was added. The precipitate settled and its height was measured. The concentration of both solutions was $1.00 mol / {dm}^{3}$ .

The experiment was repeated using different volumes of the sodium phosphate solution. The results are shown on the graph.

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What is the formula of the phosphate of metal X? Give your reasoning.

The experiment was repeated using different volumes of the sodium phosphate solution. The results are shown on the graph.

What is the formula of the phosphate of metal X? Give your reasoning.

Accepted Answer

From the graph, amount of sodium phosphate required for the complete conversion of given nitrate to its phosphate is $4 {cm}^{3}$ . After adding $5, 6 {cm}^{3}$ there is no change in the amount of product formed.

$6 {cm}^{3}$ metal nitrate requires $4 {cm}^{3}$ phosphate.

Thus, $3 {cm}^{3}$ requires $2 {cm}^{3}$ phosphate.

Thus the equation becomes,

$3 M {({NO}_{3})}_{x} + 2 {Na}_{3} {PO}_{4} \to M_{3} {({PO}_{4})}_{2}$

Thus, the formula of metal X is $M_{3} {({PO}_{4})}_{2}$ .

Richard Harwood and Ian Lodge Solutions for Chapter: Acids, Bases and Salts, Exercise 8: Exercise 5.8

Richard Harwood Chemistry Solutions for Exercise - Richard Harwood and Ian Lodge Solutions for Chapter: Acids, Bases and Salts, Exercise 8: Exercise 5.8

Questions from Richard Harwood and Ian Lodge Solutions for Chapter: Acids, Bases and Salts, Exercise 8: Exercise 5.8 with Hints & Solutions

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