Question

the reaction 2 h2o2(aq) -> 2 h2o(l) + o2(g) is first order in h2o2 and has a rate constant of 0.00785 s- at 24C. a reation vessel contains 190ml of 25% h2o2 by mass solution (density of the solution is 1.09 g/ml). the gaseous oxygen is collected over water at 24Cas it forms. What volume of o2 forms in 146 seconds at a barometric pressure of 747.9 mmHg?

Answer 1

Ans. # Step 1: Mass of H₂O₂ = Volume x Density = ( 25% x 190 mL) x (1.09 g/mL)

                                              = 51.775 g

Moles of H₂O₂ = Mass / MW = 51.775 g / 34.01468 g mol^-1 = 1.522 mol

# Step 2: Calculate moles of H₂O₂ consumed in 146 seconds

Now, moles of H₂O₂ consumed = [A]₀ – [A]_t = 1.522 mol – 0.4838 mol = 1.0382 mol

# Step 3: Following stoichiometry of balanced reaction, 2 mol H₂O₂ forms 1 mol O₂.

So, moles of O₂ formed = ½ x Moles of H₂O₂ consumed

                                       = ½ x 1.0382 mol = 0.5191 mol

Now, calculate the volume of O₂ gas using ideal equation -