The mole fraction of potassium nitrate in an aqueous solution is 0.0194. The solution's density is 1.0627 g/mL. Calculate the molarity of the solution.
A)0.0194 M
B)0.981 M
C)1.05 M
D)1.96 M
E)19.4 M

Question

Quizplus · Accepted Answer

Mole fraction of solute = moles of solute / total moles of solution
Given mole fraction of KNO3 = 0.0194
Let's assume we have 1 L of solution, then the moles of KNO3 present in it= 0.0194 * 1000 = 19.4 moles
To calculate molarity, we need to find the volume of solution in liters, which contains 19.4 moles of KNO3.
Now, let's calculate the mass of the solution containing 1L of solution (1000mL). Mass = volume * density = 1000 * 1.0627 = 1062.7 g
To find the volume of such solution containing 19.4 moles of KNO3, we need to use its molar mass (101.1 g/mol).
Mass of KNO3 = moles of KNO3 * molar mass of KNO3 = 19.4 * 101.1 = 1960.34 g
Now, we can find the volume of solution in liters which contains 19.4 moles of KNO3 by dividing its mass by density.
Volume (in liters) = Mass / Density = 1960.34 / 1.0627 = 1842.26 mL = 1.8422 L
Finally, molarity = moles / volume = 19.4 / 1.8422 = 10.536 M ≈ 1.05 M (rounded to 3 significant figures)

The Mole Fraction of Potassium Nitrate in an Aqueous Solution