NaOH has a MW of 40. A 0.12M solution is made by adding how much NaOH to 100mL of water?

.12M solution has .12M in 1L of water.

You have .1L of water, so you need .012M of NaOH.

.012M * 40g/M = .48g of NaOH

To find out how much NaOH needs to be added to 100mL of water to create a 0.12M solution, we need to use the equation:

Molarity (M) = moles of solute / volume of solution (in liters)

First, let's convert the given volume of water from mL to liters:
100mL = 100/1000 = 0.1L

Next, use the equation to solve for moles of solute:
0.12M = moles / 0.1L

Rearranging the equation to solve for moles:
moles = Molarity x Volume
moles = 0.12M x 0.1L
moles = 0.012

Now that we know we need 0.012 moles of NaOH, we can use the molecular weight (MW) of NaOH to convert moles to grams.

MW of NaOH = 40 g/mol

Grams = moles x MW
Grams = 0.012mol x 40g/mol
Grams = 0.48g

Therefore, you would need to add 0.48 grams of NaOH to 100mL of water to create a 0.12M solution.