Question

A 9.59 g sample of calcium sulfide was decomposed into its constituent elements, producing 5.33 g of calcium and 4.26 g of sulfur. Which of the statements are consistent with the law of constant composition (definite proportions)? The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%. The ratio of calcium to sulfur will vary based on how the sample was prepared. The mass ratio of Ca to S in every sample of calcium sulfide is 1.25. Every sample of calcium sulfide will have 5.33 g of calcium. Every sample of calcium sulfide will have 55.6% mass of calcium

Answer 1

Consistent statements are:

The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%.

The mass ratio of Ca to S in every sample of calcium sulfide is 1.25.

Every sample of calcium sulfide will have 55.6% mass of calcium.

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The law of constant composition states that the proportion of masses of elements present in a compound is fixed no matter what its source is or whichever way the compound is prepared.

Consistent statement 1 explanation:

In calcium sulfide or CaS, the mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%.

Mass of calcium = 5.33 g

Mass of the sample = 9.59 g

Hence, % Ca = (5.33 g x 100)/9.59 g = 55.6 %

Mass of sulfur = 4.26 g

Mass of the sample = 9.59 g

Hence, % S = (4.26 g x 100)/9.59 g = 44.4 %

Thus, % Ca + % S = (55.6 + 44.4) % = 100 %

Consistent statement 2 explanation:

In calcium sulfide or CaS, the mass ratio of Ca to S in every sample of calcium sulfide is 1.25.

ratio of %Ca : % S = 55.6 : 44.4 = 1.25 : 1

Consistent statement 3 explanation:

In calcium sulfide or CaS, every sample of calcium sulfide will have 55.6% mass of calcium.

Mass of calcium = 5.33 g

Mass of the sample = 9.59 g

Hence, % Ca = (5.33 g x 100)/9.59 g = 55.6 %

Incorrect statement:

The ratio of calcium to sulfur will vary based on how the sample was prepared.

It is incorrect because, in 1 one molecule of CaS, there will always be 1 Ca and 1 S, no matter how the CaS is prepared.

Incorrect statement:

Every sample of calcium sulfide will have 5.33 g of calcium.

This is incorrect because not every sample will have 5.33 g of Ca as long as the ratio of masses of Ca and S is 1.25. Thus a sample of CaS can contain any arbitrary mass of Ca.

For example, a sample of CaS can contain 10 g of Ca. Under this condition, the CaS must contain 10/1.25 = 8 g of S.