00:01
The chemical reaction that occurs between magnesium to produce hydrogen gas is typically a reaction with an acid.
00:11
So we've got magnesium solid reacting with h plus to produce magnesium 2 plus and hydrogen gas.
00:24
So we'll need two h pluses.
00:28
So if we have 0 .038 grams of magnesium, we can calculate the moles of hydrogen gas by dividing by the molar mass of magnesium.
00:45
One mole magnesium is 24 .305 grams.
00:54
And then one mole magnesium releases one mole h2.
01:05
So we would make 1 .56 times 10 to the negative 3 moles h2.
01:14
The pressure of h2 will be equal to the total pressure, which is provided at 746 millimeters of mercury, minus the vapor pressure of water at 244.
01:29
Celsius.
01:31
This you'll have to look up.
01:33
They didn't provide it in the problem.
01:35
At 24 degrees celsius the vapor pressure is 22 .4 millimeters of mercury.
01:44
So we need to subtract the pressure of water, hydrogen gas being collected over water, from the total pressure in order to get the pressure that just is hydrogen gas.
01:57
And we get 723 .6 millimeters...