Question

assuming a density of 1.0 g/mL, calculate the molarity and mole fraction of 3.0% h2o2

Answer 1

Is there any indication of the KIND of percent; i.e., w/w, w/v, v/v

Answer 2

no

Answer 3

ok. Let's assume it is 3% w/v so that means 3g H2O2/100 mL solution.
Convert 3g H2O2 to mols. mols = grams/molar mass
Then M = mols/L = ?mols from above/0.100 = ?

mol fraction.
mols H2O2 in 3 g H2O2 from above = ?
100 mL solution with a density of 1.0 g/mL is 100 g.
g H2O = 100 g solution total - 3g H2O2 = 97 g H2O.
mol H2O = 97g/molar mass
total mols = mols H2O + mols H2O2

Then XH2O2 = mols H2O2/total mols.
XH2O = mols H2O/total mols
Post your work if you get stuck.