Question

How many grams of NaOH are needed to make a 250.0 mL or a 4.2 M NaOH solution?

Group of answer choices

A. 1.05 grams NaOH

B. 42,000 grams NaOH

C. 42 grams NaOH

D. 1050 grams NaOH

Answer 1

C.) 42 grams NaOH

Step-by-step explanation:

To find the mass of NaOH, you need to (1) find the moles (using the molarity equation) and then (2) convert moles to grams (using the molar mass).

(Step 1)

250.0 mL / 1,000 = 0.2500 L

Molarity = moles / volume (L)

4.2 M = moles / 0.2500 L

1.05 = moles

(Step 2)

Molar Mass (NaOH): 22.990 g/mol + 15.998 g/mol + 1.008 g/mol

Molar Mass (NaOH): 39.996 g/mol

1.05 moles NaOH 39.996 g
----------------------------- x ------------------ = 42 grams NaOH
1 mole