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A 8.29g sample of calcium sulfide was decomposed into its constituent elements, producing 4.61g of calcium and 3.68g of sulfur. Which of the statements are consistent with the law of constant composition (definite proportions)?

a. Every sample of calcium sulfide will have 44.4% mass of calcium.
b. Every sample of calcium sulfide will have 2.86 g of calcium.
c. The mass ratio of Ca to S in every sample of calcium sulfide is 1.25.
d. The ratio of calcium to sulfur will vary based on how the sample was prepared.
e. The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%.

1 Answer

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Final answer:

The correct statements consistent with the law of constant composition are that each sample of calcium sulfide always has 44.4% calcium by mass, the mass ratio of calcium to sulfur is always 1.25, and the sum of the mass percentages of calcium and sulfur equals 100%.

Step-by-step explanation:

The law of constant composition (also known as the law of definite proportions) states that a chemical compound always contains exactly the same proportion of elements by mass. Therefore, consistent with this law:

  • (a) Every sample of calcium sulfide will have 44.4% mass of calcium is correct because the proportion of mass of calcium to the total mass of the compound is constant.
  • (c) The mass ratio of Ca to S in every sample of calcium sulfide is 1.25, which is calculated by dividing the mass of calcium (4.61g) by the mass of sulfur (3.68g), is also correct.
  • (e) The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100% is correct, as the sum of the mass percentages of the elements in a compound must always equal 100%.

The options b and d are incorrect. The amount of calcium in grams (2.86 g) will vary depending on the size of the sample (b), and the ratio of elements in a compound does not change based on how the sample was prepared (d).

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