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

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

Tags

NGSS.HS-PS1-7

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

Tags

NGSS.HS-PS1-7

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

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

What is the percent by mass of hydrogen in water (H2O)?

• 11.1%

• 22.2%

• 33.3%

• 44.4%

g is directly proportional to b Given g=20 when b=4. Find g when b=7

• 35

• 5

• 15

• 23

Answer explanation

Directly proportional means the one quantity equals some constant times the other quantity:

g = k·b

20 = k·4

5 = k

This goes in the formula with the new value for g to find the new value for b:

g = 5·7

g = 35

B is directly proportional to C. When B = 14, C = 7. Find the value of B when C = 5.

• 10

• 2.5

• 2

• 20

Answer explanation

Directly proportional means the one quantity equals some constant times the other quantity:

B = k·C

14 = k·7

2 = k

This goes in the formula with the new value for g to find the new value for b:

B = 2·5

B = 10

Suppose R is directly proportional to L. When R is 16, L is 24. When R is 30, L is ___.

• 38

• 20

• 40

• 45

Answer explanation

R times some number equals L

16 times some number is 24:

16·c = 24

c = 1.5

Do the same for the next set of numbers.

30·1.5 = L