Question

Potassium nitrate has a molar mass of 101.1 g per mole. In a constant pressure calorimeter, 41.8 g of potassium nitrate is dissolved in 379 g of water at 23.00°C. What is the molarity of the solution? a. 1.00 M b. 0.50 M c. 0.25 M d. 2.00 M

Answer 1

To find the molarity of a potassium nitrate solution, divide the moles of potassium nitrate (41.8 g / 101.1 g/mole) by the volume of water in liters (379 g ≈ 0.379 L), resulting in a molarity close to 1.00 M, which is the nearest given option.

Step-by-step explanation:

The molarity of a solution is defined as the number of moles of solute per liter of solution. To determine the molarity of potassium nitrate in the solution, first calculate the number of moles of potassium nitrate (KNO3).

Given that the molar mass of KNO3 is 101.1 g/mole, 41.8 g of KNO3 would contain 41.8 g / 101.1 g/mole = 0.413 moles.

Since these moles are dissolved in water to make a final volume of 379 g of water (which approximately equals to 379 mL or 0.379 L, since the density of water is about 1 g/mL), the molarity can be calculated as follows: molarity = moles/volume = 0.413 moles / 0.379 L = 1.09 M.

This value is closest to option b, which is 1.00 M, but since this isn't an exact match, the best option among the given choices is 1.00 M based on approximation.