Question

Water is decomposed into hydrogen gas and oxygen gas. What mass of water must decompose to fill a 3.00 L flask to a total pressure of 2.00 atm at 298 K with a mixture hydrogen and oxygen? 2 H2O(l) → 2 H2 (g) + O2 (g)

Answer 1

Answer:

The mass of water is 2.95 grams

Explanation:

Step 1: Data given

volume of the flask = 3.00 L

pressure = 2.00 atm

Temperature = 298 K

Step 2: The balanced equation

2 H2O → 2 H2 + O2

For 2 moles of H2O, there are produce 2 moles of H2 and 1 mole of O2 produced ( total moles of gas = 3)

Step 3: Calculate moles of gas

PV = nRT  

n = PV / RT = (2.00 atm) * (3.00 L) / ((0.08206 L atm/K mol) * (298 K))

n =0.2454 mol gases

Step 4: Calculate mass of H2O

Mass of H2O = (0.2454 mol gases) * (2 mol H2O / 3 mol gases) * (18.02 g H2O/mol)

Mass of H2O = 2.948 g H2O

The mass of water is 2.95 grams