Question

Groundwater contains 1.5mM potassium nitrate (101.1 g/mol) and 0.01% magnesium sulfate (120.4 g/mol). How many grams of each substance is in 125 mL of groundwater?

A. 2.52 g of potassium nitrate, 0.015 g of magnesium sulfate
B. 1.51 g of potassium nitrate, 0.012 g of magnesium sulfate
C. 3.18 g of potassium nitrate, 0.002 g of magnesium sulfate
D. 2.10 g of potassium nitrate, 0.0015 g of magnesium sulfate

Answer 1

To calculate the grams of each substance in the given volume of groundwater, we need to use the molarity and the volume. The correct answer is B. 1.51 g of potassium nitrate, 0.012 g of magnesium sulfate.

Step-by-step explanation:

Molarity is a way to measure the concentration of a substance in a solution. To calculate the grams of each substance in the given volume of groundwater, we need to use the molarity and the volume.

For potassium nitrate:

Molarity of potassium nitrate = 1.5 mM = 1.5 mol/L.

Number of moles of potassium nitrate = 1.5 mol/L × 0.125 L = 0.1875 mol.

Mass of potassium nitrate = 0.1875 mol × 101.1 g/mol = 18.988 g.

For magnesium sulfate:

Percentage of magnesium sulfate = 0.01% = 0.01 g/100 g.

Mass of magnesium sulfate in 125 mL of groundwater = 0.01 g/100 g × 125 mL = 0.0125 g.

Therefore, the correct answer is B. 1.51 g of potassium nitrate, 0.012 g of magnesium sulfate.