Answer
9.79 M
Work Step by Step
$30\%$ $H_{2}O_{2}$ means that 100.g solution contains 30.0g $H_{2}O_{2}$.
Molar mass of $H_{2}O_{2}=34.0147\,g/mol$
Number of moles $n= \frac{mass\,in\,grams}{Molar\,mass}$
$=\frac{30.0\,g}{34.0147\,g/mol}=0.8819716\,mol$
Volume of the solution V=
$\frac{mass\,of\,the\, solution}{Density\,of\, the\, solution}=\frac{100\,g}{1.11\,g/mL}$
$=90.09\,mL=0.09009\,L$
Molarity=$\frac{n}{V}=\frac{0.8819716\,mol}{0.09009\,L}=9.79\,M$
