Can somebody please answer this question

Question

In lab you are required to make 250 mL of a 0.4 M NaOH solution. How many grams of NaOH should you measure out to make the solution? Round your answer to the nearest whole number.

Answer 1

Whenever you see a problem with molarity (M), assume that you will need the equation

Molarity = moles

Litters

(M = mol / L)

The question gives us the molarity of NaOH and the milliliters of solution, so what we can do is plug in those values to find the moles of NaOH, then convert them into grams, like so:

0.4 M NaOH= x mols NaOH

0.25 L NaOH

note: the formula will only work if you plug in L, so you may need to convert the given units to L

mols NaOH = 0.4 M NaOH x 0.25 L NaOH = 0.1 mols NaOH

now that we can use stoichiometry to convert the moles of NaOH to grams

0.1 mol NaOH x 1 g NaOH / 39.997 mols NaOH

edit: make sure to that your units properly cancel. If not, you may have multiplied where you need to divide or vice versa.

= 0.0025001875 g NaOH or 2.5x10³ g NaOH

Hope this helps.