What is the final molarity of..... (see below)?

Question

A student prepares a solution by dissolving 3.81 g of NaOH in enough water to make 300. mL of solution.
The student then transfers 25.0 mL of this solution into a 100. mL volumetric flask. Water is then added
up to the 100. mL mark.
What is the final molarity of NaOH in the 100. mL flask ?


Enter a numeric answer only, don't include units in your answer.

Answer 1

1) Calculate the number of moles of NaOH in 300 mL
3.81 g /( 22.99+16+1.008) = 0.0955 mol

2) Calculate the number of moles of NaOH in the 25 mL transfered
0.0955 mol * 25/300 = 7.96 x 10^-3 mol

3) Calculate the molarity
7.96 x 10^-3 mol / 100 mL = 0.0796 mol/liter

Answer 2

change grams to moles by dividing by the molecular mass of NaOH

Molarity = moles/liters - calculate the molarity of the solution using 300 mL (changed to liters) as the volume.

Then use the dilution formula: C1 x V1 = C2 x V2 to figure out the dilution.

C1 = your concentration from the first part
V1 = 25 mL
V2 = unknown
C2 = 100 mL