If 70.0 mL of water is added to 30.0 mL of 0.400 M solution of NaOH, what is the new concentration of NaOH?

. 4 mol/liter = .0004 mol/mL

30 * .0004 = 0.012 mol NaOH

.012 mol NaOH in 100 mL is .12 mol/liter

To find the new concentration of NaOH after adding water, you need to use the formula for dilution:

C1V1 = C2V2

where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.

Given:
C1 (initial concentration of NaOH) = 0.400 M
V1 (initial volume of NaOH solution) = 30.0 mL
V2 (final volume after adding water) = 30.0 mL + 70.0 mL = 100.0 mL

Now, let's plug these values into the formula:

(0.400 M)(30.0 mL) = C2(100.0 mL)

To solve for C2 (the final concentration of NaOH), rearrange the equation:

C2 = (0.400 M)(30.0 mL) / 100.0 mL

C2 = 0.120 M

Therefore, the new concentration of NaOH after adding 70.0 mL of water is 0.120 M.