Question

A 37.5 mL solution contains 0.181 g of potassium chromate, K₂CrO₄. What is the molarity?

0.025 M
0.125 M
0.005 M
0.250 M

Answer 1

To calculate the molarity of the potassium chromate solution, convert the given mass to moles, the volume from mL to L, and divide moles by liter. The result is approximately 0.025 M, which is the correct answer option.

Step-by-step explanation:

To find the molarity of the potassium chromate solution, we need to calculate the number of moles of potassium chromate and divide it by the volume of the solution in liters. First, we find the molar mass of potassium chromate (K₂CrO₄) which is approximately 194.19 g/mol.

Next, we convert the mass of potassium chromate into moles:

0.181 g K₂CrO₄ × (1 mol K₂CrO₄ / 194.19 g K₂CrO₄) = 0.000932 moles K₂CrO₄

Finally, we convert the volume of the solution from milliliters to liters and calculate the molarity:

37.5 mL × (1 L / 1000 mL) = 0.0375 L

Molarity (M) = moles of solute / liters of solution = 0.000932 moles K₂CrO₄ / 0.0375 L = 0.02485 M

The calculated molarity of the potassium chromate solution is approximately 0.025 M, which is the closest to the given option of 0.025 M.