Question

Let's assume that in the Iodide-catalyzed Decomposition of Hydrogen Peroxide experiment, you were supposed to use 21.0 % H₂O₂ (volume) solution instead. What is the molarity, in mol/L, of the H₂O₂, if the solution has a density of 1.124 g/mL? The molar mass of H₂O₂ is 34.0147 g/mol. Report the answer to two place after the decimal. Do not include units.

Answer 1

To find the molarity of a 21.0% volume solution of H2O2 with a density of 1.124 g/mL, convert volume percent to mass, calculate the mass of H2O2, convert mass to moles, and then adjust for solution volume to get 6.94 mol/L.

Step-by-step explanation:

To calculate the molarity of a 21.0 % (volume) H2O2 solution with a density of 1.124 g/mL, we initially convert this percentage into a mass/volume percentage, as 21.0 % (v/v) implies there are 21.0 mL of H2O2 in every 100 mL of solution. Now we need the mass of H2O2 in this volume, which we get by using the density.

First, calculate the mass of 21.0 mL of H2O2:
21.0 mL × 1.124 g/mL = 23.604 g H2O2.
Next, convert this mass into moles using the molar mass of H2O2:
23.604 g ÷ 34.0147 g/mol = 0.694 moles of H2O2.

Since the density is given for the entire solution, we can assume that 100 mL of solution has a mass of:
100 mL × 1.124 g/mL = 112.4 g.
The number of moles of H2O2 in 100 mL then needs to be converted to moles per liter (molarity).
Since 100 mL is 1/10 of a liter, it follows that:
0.694 moles × 10 = 6.94 mol/L.