What would be the balanced equation?

Question

In the electrolytic decompostition of water, what maximum volume of oxygen gas could be produced at 15 degrees celcius, and 100.5 kPa if 250 g of water are decomposed?

What would be the balanced equation?

Answer 1

For the maximum volume, use the ideal gas law:
PV = nRT

Where P = pressure in Pa
V = volume
n = # moles
R = gas constant 8.3143 m3·Pa·K-1·mol-1
T = temperature in Kelvin

100500V = (250)/18 * 8.3143 * (15+273.15)
V = .33 m^3

Answer 2

The balanced equation for the decomposition is:
2H2O(l) ==> 2H2(g) + O2(g)
You can get the # of moles of H2O from the given mass. Then based on the balanced equation the moles of O2 produced would be half of the total moles of H2O. Given the temp, pressure and no. of moles, you can easily compute for the volume of oxygen using the ideal gas equation PV=nRT; V=nRT/P, just make sure you convert the temp into K, pressure into atm, then use R=0.0821 L-atm/mol K. You'll get the volume in L.

Answer 3

2H2O ===> 2H2 + O2

Atomic weights: H=1 O=16 O2=32 H2O=18

250gH2O x 1molH2O/18gH2O x 1molO2/2molH2O 22.4LO2/1molO2 = 156L O2 at STP. Convert to 288K and 100.5kPa, and you're home!