Final answer:
To calculate the concentration of an aqueous hydrogen peroxide solution, divide 0.0025 moles of oxygen gas by the volume of the solution in dm3 (0.05 dm3), resulting in a concentration of 0.05 mol/dm3.
Step-by-step explanation:
The student's question involves calculating the concentration of an aqueous hydrogen peroxide solution in mol/dm3 using a given amount of oxygen gas moles. The formula for concentration is moles of solute divided by the volume of solution in dm3. As the student has used 0.0025 moles of oxygen gas (O2) and the volume of hydrogen peroxide (H2O2) solution is 50 cm3, which is equivalent to 0.05 dm3 (since 1 dm3 = 1000 cm3), the concentration would be calculated as follows:
Concentration = moles of solute / volume of solution in dm3 = 0.0025 mol / 0.05 dm3 = 0.05 mol/dm3.
Thus, the concentration of the aqueous hydrogen peroxide solution used is 0.05 mol/dm3.