First, let's write the balanced chemical reaction:
2 H2O2 ---MnO2--> 2 H2O + O2
This reaction is a b. Decomposition Reaction of hydrogen peroxide.
Step 1. Let's transform 2.11 mg of H2O2 into moles using the following equation mole = mass / molar mass
Step 2. We are going to use the equation proportion to calculate the quantity in moles of each compound.
Step 3. We are going to transform moles into grams of each compound using the following equation: mass = mole x molar mass
Step 1.
We need to transform 2.11 mg to g. We just need to divide by 1000,
So: 2.11 x 10^-3 g of H2O
mole = 2.11 x 10^-3/34.02
mole = 6.20 x 10^-5 moles
Step 2.
2 moles of H2O2 ---- 2 moles of H2O
6.20 x 10^-5 moles ---- x moles of H2O
x = 6.20 x 10^-5 moles of H2O
2 moles of H2O2 ---- 1 moles of O2
6.20 x 10^-5 moles ---- x moles of O2
x = 3.10 x 10^-5 moles of O2
Step 3.
molar mass of O2 : 32 g/mol
molar mass of H2O: 18 g/mol
mass of H2O = 6.20 x 10^-5 x 18 = 1.12 x 10^-3 g
mass of O2 = 3.10 x 10^-5 x 32 = 9.92 x 10^-4 g