Household hydrogen peroxide is an aqueous solution containing 3.0% hydrogen peroxide by mass. What is the molarity of this solution? (Assume a density of 1.01 g/mL.)

Verified step by step guidance

1. Step 1: Understand the problem. We are given that the solution is 3.0% hydrogen peroxide by mass. This means that in 100 g of the solution, there are 3.0 g of hydrogen peroxide (H2O2).
2. Step 2: Calculate the number of moles of H2O2 in the solution. The molar mass of H2O2 is approximately 34.01 g/mol. So, the number of moles of H2O2 in 100 g of the solution can be calculated using the formula: moles = mass (g) / molar mass (g/mol).
3. Step 3: Determine the volume of the solution. We are given that the density of the solution is 1.01 g/mL. Since we are considering 100 g of the solution, the volume of the solution can be calculated using the formula: volume (L) = mass (g) / density (g/mL). Remember to convert the volume from mL to L for molarity calculation.
4. Step 4: Calculate the molarity of the solution. Molarity (M) is defined as the number of moles of solute per liter of solution. So, the molarity of the solution can be calculated using the formula: M = moles / volume (L).
5. Step 5: Substitute the values obtained in steps 2 and 3 into the formula in step 4 to calculate the molarity of the hydrogen peroxide solution.

Key Concepts

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in units of moles per liter (mol/L). To calculate molarity, one must know the amount of solute in moles and the total volume of the solution in liters.

Density

Density is the mass of a substance per unit volume, typically expressed in grams per milliliter (g/mL) or kilograms per cubic meter (kg/m³). In this context, the density of the hydrogen peroxide solution is used to convert the mass of the solution into volume, which is essential for calculating molarity.

Percent by Mass

Percent by mass is a way to express the concentration of a solution, indicating the mass of solute present in a given mass of solution. In this case, a 3.0% hydrogen peroxide solution means that there are 3.0 grams of hydrogen peroxide in every 100 grams of the solution, which is crucial for determining the number of moles of solute.