Two samples of sodium chloride were decomposed into their constituent elements.

Question

Two samples of sodium chloride were decomposed into their constituent elements. One sample produced 2.79 g of sodium and 4.30 g of chlorine. Which of the following could be the results of the decomposition of the other sample, being consistent with the law of constant composition (also called the law of definite proportions or law of definite composition)?

5.11 g of sodium and 4.09 g of chlorine

5.11 g of sodium and 1.43 g of chlorine

5.11 g of sodium and 12.8 g of chlorine

5.11 g of sodium and 7.87 g of chlorine

Explanation / Answer

Explanation: According to the law of constant composition states for a given chemical compound always contains its component elements in fixed ratio (means by its weight) and does not depend on its source and method of preparation.

Molar mass of Sodium (Na) is 22.99 g/mol

Molar mass of Chloride (Cl) is 35.45 g/mol

Sodium chloride (NaCl)= contains 22.99 g/mol of sodium and 35.45 g/mol Chloride.

For first sample calculation in the given data 2.79 g of sodium and 4.30 g of chlorine

The results of the decomposition of the other sample, being consistent with the law of constant composition

In another sample, it contains 5.11 g of sodium (which is constant in all the options). What is the weight of Chloride (Cl)/ Chloride (Cl2)

Amount of chlorine produced by decomposition of another sample is

= [35.45 g/mol (Molar mass of Chloride) X 5.11 g (weight of Sodium produced)]/ 22.99 g/mol (Molar mass of sodium)

=7.87 g

Therefore, the right answer is option is “D. 5.11 g of sodium and 7.87 g of chlorine”

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