Proportions and Percent Proportions

a compound is always composed of the same element in the same proportion by mass

• element

• law of multiple proportions

• law of definite proportions

• percent by mass

The mass of an unknown element would be _ if the percentage of it in a 44.01 g compound was 27.29%.

• 1.613 g

• 12.01 g

• 62.01 g

• 72.71%

What does the law of definite proportions state in chemistry?

• It states that a compound is always composed of the same elements in the same proportion by mass.

• It states that elements can combine in different ratios to form different compounds.

• It states that the mass of reactants equals the mass of products in a chemical reaction.

• It states that the properties of elements are periodic functions of their atomic numbers.

Which law is used to calculate the percent composition of a compound?

• Law of conservation of mass

• Law of definite proportions

• Law of multiple proportions

• Avogadro's law

If a compound is composed of 40% sulfur and 60% oxygen by mass, what is the percent by mass of sulfur in the compound?

• 40%

• 50%

• 60%

• 70%

In a chemical reaction, the ratio of the mass of hydrogen to oxygen in water is always 1:8. What does this illustrate?

• Law of conservation of mass

• Law of definite proportions

• Law of multiple proportions

• Avogadro's law

What is the percent by mass of carbon in carbon dioxide (CO2)?

• 27.3%

• 44.4%

• 72.7%

• 100%

Which of the following is an example of a percent proportion in biology?

• The percentage of oxygen in the atmosphere

• The ratio of red blood cells to white blood cells

• The percentage of water in the human body

• The ratio of nitrogen to oxygen in the air

A solution is made by dissolving 10g of salt in 90g of water. What is the percent concentration of salt in the solution?

• 10%

• 11%

• 9%

• 12%

In a mixture of gases, the proportion of nitrogen is 78%. What is this an example of?

• Percent by volume

• Percent by mass

• Mole fraction

• Partial pressure