Under certain conditions, water can be separated into oxygen and hydrogen gases according to the equation 2H2O → 2H2 + O2.
In a lab, 112g of hydrogen gas and 888g of oxygen gas were collected. Student A says that the amount of water to start cannot be determined, but Student B says that the water must have been 1000g. Who is correct?
To determine who is correct, we can analyze the equation for the reaction:
2H2O → 2H2 + O2
According to the equation, 2 moles of water produce 2 moles of hydrogen gas and 1 mole of oxygen gas.
To calculate the molar mass of water, we add the molar masses of hydrogen and oxygen:
(2 * 1.008) + (16.00) = 18.016 g/mol
Now we can calculate the number of moles of hydrogen gas collected:
112g / (2 * 2.016 g/mol) = 28 mol
And the number of moles of oxygen gas collected:
888g / 32.00 g/mol = 27.75 mol
Since the ratio of moles of hydrogen to oxygen is 2:1, and the number of moles of oxygen is slightly less than the number of moles of hydrogen, it implies that the oxygen gas hasn't been completely collected.
To determine the initial amount of water, we need to consider the limiting reactant, which is oxygen gas in this case.
From the equation, we can determine that 1 mole of oxygen gas is produced from 2 moles of water. So, 27.75 mol of oxygen gas is produced from (27.75 mol / 2 mol) = 13.875 mol of water.
Now, we can calculate the mass of water:
13.875 mol * 18.016 g/mol = 249.98 g
Therefore, Student B is correct. The initial amount of water must have been approximately 250 grams.