Question

How many liters of H2 are required to form 5 moles of H2O at STP?

Answer 1

steps...

1) convert mass H2O to moles H2O

2) use coefficients of balanced equation to convert to moles O2

3) convert moles O2 to L O2.

solution...

10.5 g H2O x (1 mole H2O / 18.0 g H2O) = 0.583 moles H2O

from the balanced equation, 1 mole O2 --> 2 moles H2O.. therefore...

0.583 moles H2O x (1 mole O2 / 2 moles H2O) = 0.292 moles O2

from here you can either use the specific form of the ideal gas law for STP...

0.292 moles O2 x (22.4 L O2 / mole O2) = 6.54 L O2

or you can use the more general form of the ideal gas law...

V = nRT/P = (0.292 moles) x (0.0821 Latm/moleK) x (273 K) / (1 atm)

V = 6.54 L O2

Hope this helps!