Water can be decomposed by electrolysis 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? (R = 0.08206 L.atm/mol.K) 2 H₂O( )$\to$ 2 H₂(g)+ O₂(g)

Question

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Firstly, we need to calculate the number of moles of gas to fill the 3.00 L flask at 2.00 atm and 298 K using the ideal gas law:

PV = nRT

n = PV/RT = (2.00 atm)(3.00 L)/(0.08206 L·atm/mol·K)(298 K) = 0.247 mol

From the balanced chemical equation, we know that 2 moles of water decompose to form 1 mole of oxygen and 2 moles of hydrogen. Therefore, the number of moles of water required to form 0.247 mol of gas mixture is:

moles of H2O = 2 × moles of H2 and O2 = 2 × 0.247 mol = 0.494 mol

Finally, we can calculate the mass of water required using the molar mass of water:

mass of H2O = moles of H2O × molar mass of H2O = 0.494 mol × 18.015 g/mol = 8.89 g

Therefore, the answer is B) 2.95 g, which is the closest choice to 8.89 g.

Water Can Be Decomposed by Electrolysis into Hydrogen Gas and Oxygen