Turning w/v into molarity:

Question

jfraser · Answer

3% $H_2O_2$ is a mass/volume concentration, which can be turned into molarity fairly easily. 3% w/v means for every 100mL of solution, there are 3g of solute, in this case, $H_2O_2$. Conversion factors will do the rest
$$\frac{3g H_2O_2}{100mL}*\frac{1 mol H_2O_2}{34g H_2O_2}*\frac{1000mL}{1L}$$gets a molarity of 0.88M.

Now this can be used in equations of rate, equilibrium, or anything else that needs a concentration in mol/L

jfraser · Answer

@Frostbite

jfraser · Answer

well your problem was 30%, not 3%, so the starting concentration is 8.8M, not 0.88M, then diluted 50x, so the starting concentration of H2O2 in the formula is 0.176M

frostbite · Answer

Oh yeah, forgot it was 30% currently I'm everywhere else than in general chemistry.
Sounds about correct. Thanks.