Final answer:
The concentration of aqueous hydrogen peroxide at the start of the experiment was calculated to be 0.080 mol/dm³ after determining the number of moles of oxygen produced, deducing the moles of hydrogen peroxide that decomposed, and dividing by the initial volume of the hydrogen peroxide solution.
Step-by-step explanation:
To calculate the concentration of aqueous hydrogen peroxide at the start of the experiment, we need to follow a series of steps involving stoichiometry. First, we calculate the number of moles of oxygen formed using the volume of oxygen gas collected at room temperature and pressure (r.t.p.) and the ideal gas law. Then, we use the balanced chemical equation to deduce the number of moles of hydrogen peroxide that decomposed. Finally, we use the initial volume of the hydrogen peroxide solution and the number of moles of hydrogen peroxide to calculate its concentration in moles per decimeter cubed (mol/dm³).
Assuming one mole of gas occupies 24.0 dm³ at r.t.p., we calculate the number of moles of O₂ formed:
- Number of moles of O₂ = Volume of O₂ (dm³) / 24.0 dm³/mol
= 0.048 dm³ / 24.0 dm³/mol = 0.002 mol O₂ - Using the stoichiometric coefficients from the balanced equation (2 H₂O₂ → 2 H₂O + O₂), we deduce that the number of moles of H₂O₂ that decomposed is equal to the number of moles of O₂ formed.
Number of moles of H₂O₂ decomposed = 0.002 mol O₂ - To find the concentration of hydrogen peroxide, we use the initial volume of H₂O₂ solution:
Concentration of H₂O₂ = Moles of H₂O₂ / Volume of H₂O₂ solution (in dm³)
= 0.002 mol / 0.025 dm³ = 0.080 mol/dm³
The concentration of aqueous hydrogen peroxide at the start of the experiment was 0.080 mol/dm³.