KClO3 decomposes to produce oxygen gas. If at the end of the reaction, 2.0 L of oxygen gas was collected in a flask by displacing water at 28 °C and 810 mmHg. Calculate the mass of KClO3 decomposed. The vapor pressure of water at 28 °C is 28.3 mmHg. (Hint: The gases collected are a mixture of oxygen and water vapor. What is the partial pressure of oxygen?) 2 KClO3 (s) ? 2 KCl (s) + 3 O2 (g)