Question 1

Which statement best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same ratio by mass.

Question 2

Given the mass ratio of oxygen to carbon in $$CO_2 is$$ $$2.67:1$$, what is the mass of oxygen in $$8.00 \ g of$$ $$CO_2$$?

Accepted Answer

$$5.34 \ g$$

Question 3

If a compound contains $$2.00 \ g of $$sodium and $$3.00 \ g of $$chlorine, what is the mass ratio of sodium to chlorine?

Accepted Answer

$$0.67:1$$

Question 4

Two samples of a compound are analyzed. Sample A contains $$12.0 \ g of $$hydrogen and $$32.0 \ g of $$oxygen. Sample B contains $$11.0 \ g of $$hydrogen and $$29.3 \ g of $$oxygen. Do these samples represent the same compound according to the Law of Definite Proportions?

Accepted Answer

Yes, because the mass ratios are nearly identical.

Question 5

A $$7.14 \ g$$ sample of HCN is found to contain $$0.287 \ g of H $$and $$4.41 \ g of N. $$What is the mass of carbon in the sample?

Accepted Answer

$$2.43 \ g$$

Question 6

If a compound contains $$2.00 \ g of $$sodium and $$3.00 \ g of $$chlorine, how much sodium would be present in $$6.00 \ g of $$chlorine in the same compound?

Accepted Answer

$$4.00 \ g$$

Question 7

Which of the following best illustrates the Law of Definite Proportions?

Accepted Answer

Water from different sources always contains hydrogen and oxygen in a $$1:8$$ ratio by mass.

Question 8

A compound contains $$4.00 \ g of $$element X and $$6.00 \ g of $$element Y. If another sample of the same compound contains $$10.0 \ g of $$element Y, how much element X should it contain?

Accepted Answer

$$6.67 \ g$$

Question 9

If a $$15.0 \ g$$ sample of a compound contains $$5.0 \ g of $$element A and $$10.0 \ g of $$element B, what is the mass ratio of A to B?

Accepted Answer

$$1:2$$

Question 10

A compound is found to contain $$2.00 \ g of $$sodium and $$3.00 \ g of $$chlorine. If a sample contains $$4.00 \ g of $$sodium, how much chlorine should it contain to be the same compound?

Accepted Answer

$$6.00 \ g$$

Question 11

Which of the following is NOT a consequence of the Law of Definite Proportions?

Accepted Answer

Different samples of a compound have different mass ratios of elements.

Question 12

A $$10.0 \ g$$ sample of a compound contains $$2.5 \ g of $$hydrogen and $$7.5 \ g of $$oxygen. What is the mass ratio of hydrogen to oxygen?

Accepted Answer

$$1:3$$

Question 13

If a compound contains $$2.00 \ g of $$sodium and $$3.00 \ g of $$chlorine, what is the percentage by mass of sodium in the compound?

Accepted Answer

$$40\%$$

Question 14

A $$20.0 \ g$$ sample of a compound contains $$8.0 \ g of $$element X and $$12.0 \ g of $$element Y. What is the mass ratio of X to Y?

Accepted Answer

$$0.67:1$$

Question 15

If a $$7.14 \ g$$ sample of HCN contains $$0.287 \ g of H $$and $$4.41 \ g of N$$, what is the percentage by mass of carbon in the sample?

Accepted Answer

$$34.0\%$$

Question 16

A compound contains $$2.00 \ g of $$sodium and $$3.00 \ g of $$chlorine. If a sample contains $$9.00 \ g of $$chlorine, how much sodium should it contain to be the same compound?

Accepted Answer

$$6.00 \ g$$

Question 17

Which of the following compounds would NOT obey the Law of Definite Proportions?

Accepted Answer

A compound whose samples have different mass ratios of elements.

Question 18

A $$15.0 \ g$$ sample of a compound contains $$5.0 \ g of $$element A and $$10.0 \ g of $$element B. What is the percentage by mass of element B?

Accepted Answer

$$66.7\%$$

Question 19

If a $$7.14 \ g$$ sample of HCN contains $$0.287 \ g of H $$and $$4.41 \ g of N$$, what is the mass ratio of N to H?

Accepted Answer

$$15.4:1$$

Law of Definite Proportions and Mass Ratios

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