A student prepared a stock solution by dissolving 20.0 g of NaOH in enough water to make 150.mL of solution.She then took 15.0 mL of the stock solution and diluted it with enough water to make 65.0 mL of a final solution.What is the concentration of NaOH for the final solution?
A)0.769 M
B)0.548 M
C)1.40 M
D)1.82 M

Question

Quizplus · Accepted Answer

First, calculate the molarity of the stock solution: moles of NaOH = 20.0 g / 40.00 g/mol (molar mass of NaOH) = 0.500 mol. Molarity of stock solution = moles/volume = 0.500 mol / 0.150 L = 3.33 M. Then, use the dilution formula M1V1 = M2V2, where M1 = 3.33 M, V1 = 0.015 L, V2 = 0.065 L. Solving for M2 gives M2 = (3.33 M)(0.015 L) / 0.065 L = 0.769 M.

A Student Prepared a Stock Solution by Dissolving 20