Question

The first task you are assigned in your summer laboratory job is to prepare a concentrated NaOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 mL solution that has a concentration of 10 M?

(a) 800 g
(b) 200 g
(c) 400 g
(d) 160 g

Answer 1

To prepare a 500 mL solution of 10 M NaOH, one must weigh out 200 grams of NaOH, using the molarity formula and the molar mass of NaOH.

Step-by-step explanation:

To determine how many grams of solid NaOH are needed to prepare a 500 mL solution with a concentration of 10 M, we need to use the formula of molarity (M), which is moles of solute per liters of solution (M = moles/L).

First, we find the number of moles of NaOH required for the solution:

10 M = moles of NaOH / 0.500 L (since 500 mL is 0.500 L)

Moles of NaOH needed = 10 M * 0.500 L = 5 moles

Using the molar mass of NaOH (40.00 g/mol), we then convert the moles of NaOH to grams:

Mass of NaOH = Moles * Molar mass

Mass of NaOH = 5 moles * 40.00 g/mol = 200 g

Therefore, you will need to weigh out 200 grams of solid NaOH.