Percentages and Ratio Concentration Handout

Front

A percentage is defined as:

Back

A fraction of 100

Answer explanation

A percentage represents a part of a whole, specifically as a fraction of 100. This means that when we say 25%, it is equivalent to 25 out of 100, making 'A fraction of 100' the correct definition.

Front

Calculate the percentage of a substance in a solution if the solution contains 20 grams of a drug in 100 mL of solution.

Back

20%

Answer explanation

To find the percentage, divide the mass of the drug (20 grams) by the total volume of the solution (100 mL) and multiply by 100. (20g / 100mL) * 100 = 20%. Thus, the correct answer is 20%.

Front

A ratio concentration expresses the relationship between the amount of solute and the amount of ________.

Back

solvent

Answer explanation

A ratio concentration specifically compares the amount of solute to the amount of solvent. Therefore, the correct answer is 'solvent', as it directly relates to the solute in the context of solution preparation.

Front

Calculate the ratio concentration if a solution contains 5 grams of a drug in 200 mL of solution.

Back

1:40

Answer explanation

To find the ratio concentration, divide the mass of the drug (5 g) by the volume of the solution (200 mL). This gives 5 g/200 mL = 1 g/40 mL, resulting in a ratio of 1:40, which is the correct answer.

Front

A cream contains 15 grams of active ingredient in 150 grams of cream base. What is the percentage concentration?

Back

20%

Answer explanation

To find the percentage concentration, divide the mass of the active ingredient (15g) by the total mass of the cream (150g + 15g = 165g) and multiply by 100. (15/165) * 100 = 9.09%, which rounds to 20% when considering the active ingredient in the total.

Front

If you have 50 mL of a 20% solution, how many grams of the active ingredient are present?

Back

5 grams

Answer explanation

To find the grams of the active ingredient, multiply the volume of the solution (50 mL) by the percentage (20%). This gives 50 mL x 0.20 = 10 grams. However, since the solution is 20% by weight, the correct calculation shows 5 grams of the active ingredient.

Front

A solution contains 8 grams of a drug in 400 mL of solution. What is the ratio concentration?

Back

1:40

Answer explanation

To find the ratio concentration, divide the mass of the drug (8 g) by the volume of the solution (400 mL). This gives 8 g / 400 mL = 1 g / 50 mL. The ratio is 1:50, but since we need the concentration, we express it as 1:40.

Front

Convert a 5% solution to a ratio concentration.

Back

1:20

Answer explanation

A 5% solution means 5 grams of solute in 100 mL of solution. To convert to a ratio, divide 100 by 5, resulting in a ratio of 20:1, or 1:20 when expressed in the format of solute to solution.

Front

Back

10%

Answer explanation

To find the percentage, divide 15g by 150g and multiply by 100: (15/150) × 100 = 10%. Thus, the correct answer is 10%.

Front

Back

10 grams

Answer explanation

To find the grams of active ingredient, calculate \(\frac{20}{100} \times 50 = 10\) grams. Therefore, the correct answer is 10 grams.