Problem: The reaction 2H2O2(aq)→2H2O(l)+O2(g) is first order in H2O2 and under certain conditions has a rate constant of 0.00752 s−1 at 20.0 °C. A reaction vessel initially contains 150.0 mL of 30.0% H2O2  by mass solution (the density of the solution is 1.11 g/mL). The gaseous oxygen is collected over water at 20.0°C as it forms.What volume of O2 will form in 41.3 seconds at a barometric pressure of 721.1 mmHg. (The vapor pressure of water at this temperature is 17.5 mmHg)

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Step 1. Initial moles of H2O2

g total gas= 150 mL 1.11 g1 mLg total gas = 166.5 gmoles H2O2 = 30% (166.5 g)1 mol34 gmoles H2O2 =1.47 mol


Step 2. Moles of left after 41.3 seconds 

1st order reaction:lnAt = -kt +lnA0ln[A]t = -0.00752 s-141.3 s+ln1.47 molln[A]t =0.0747 molAt = 1.078 mol

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Problem Details

The reaction 2H2O2(aq)→2H2O(l)+O2(g) is first order in H2O2 and under certain conditions has a rate constant of 0.00752 s−1 at 20.0 °C. A reaction vessel initially contains 150.0 mL of 30.0% H2O2  by mass solution (the density of the solution is 1.11 g/mL). The gaseous oxygen is collected over water at 20.0°C as it forms.

What volume of O2 will form in 41.3 seconds at a barometric pressure of 721.1 mmHg. (The vapor pressure of water at this temperature is 17.5 mmHg)

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