Question

How many liters of oxygen gas can be produced if 28.7 grams of water decomposes at 294 Kelvin and 0.986 atmospheres? Show all of the work used to solve this problem. 2H2O (l) yields 2H2 (g) + O2 (g)

Answer 1

1) Chemical reaction:

2H2O (l) ---> 2H2 (g) + O2(g)

2) molar ratios

2 mol H2O (l) : 2 mol H2(g) : 1 mol O2(g)

3) convert 28.7 grams of H2O into moles

number of moles = mass in grams / molar mass = 28.7 g / 18.0 g/mol = 1.594 mol

4) use proportions to calculate the number of moles of O2

1mol O2 / 2mol H2O * 1.594 mol H2O = 0.797 mol O2.

5) use pV = nRT to calculate V

V = nRT / p = 0.797 mol * 0.0821 atm*l /K*mol * 294K / 0.986 atm = 19.5 l

Answer: 19.5 liter