The bottle of hydrogen peroxide from the store says it is a 3% solution by mass. What is its molal concentration?

3% by mass means 3 g H2O2 and 97 g H2O.

3 g H2O2 = ?? mols. mols =g/molar mass
Then molality = mols/kg solvent. Post your work if you need additional assistance.

To find the molal concentration of the hydrogen peroxide solution, we need to know the molar mass of hydrogen peroxide (H2O2) and the mass of the solute (hydrogen peroxide) in the solution.

Step 1: Find the molar mass of hydrogen peroxide (H2O2):
The molar mass of hydrogen (H) is 1 g/mol, and the molar mass of oxygen (O) is 16 g/mol. Since there are two atoms of hydrogen and two atoms of oxygen in hydrogen peroxide, we can calculate the molar mass as follows:
Molar Mass of H2O2 = (2 * Molar Mass of H) + (2 * Molar Mass of O)
= (2 * 1 g/mol) + (2 * 16 g/mol)
= 2 g/mol + 32 g/mol
= 34 g/mol

Step 2: Calculate the amount of solute (hydrogen peroxide) in the solution:
A 3% solution by mass means that there are 3 grams of solute (hydrogen peroxide) in 100 grams of solution. So, if we have 100 grams of solution, we have 3 grams of hydrogen peroxide.

Step 3: Calculate the molal concentration:
Molal Concentration (in mol/kg) = Moles of Solute / Mass of Solvent (in kg)

Since water is typically used as a solvent for hydrogen peroxide solutions, we need to convert the mass of water to kilograms. The density of water is 1 g/mL, so 100 grams of water is equivalent to 100 mL or 0.1 L, which is equal to 0.1 kg.

Moles of Solute = Mass of Solute (in grams) / Molar Mass of Solute
= 3 g / 34 g/mol
= 0.088 moles

Molal Concentration = 0.088 moles / 0.1 kg
= 0.88 mol/kg

Therefore, the molal concentration of the 3% hydrogen peroxide solution is 0.88 mol/kg.