00:01
Hi there.
00:03
In this question, we are given this balanced chemical equation, and we want to know how many grams of hydrogen gas are going to be produced if we react six grams of magnesium with excess hydrochloric acid.
00:19
Okay, so this is what we have.
00:21
We're trying to convert from grams magnesium to grams of hydrogen.
00:25
So this is a mass -to -mass, stochometry problem.
00:29
And in any stochometry problem, at some point we need to use.
00:33
Mole ratio because that's how we get from one substance to the other.
00:38
And the mole ratio comes from the coefficients in the balanced equation.
00:42
Well, since there is nothing written in front of magnesium or the hydrogen, we know that it's a one -to -one mole ratio between these two.
00:51
Well, to use that mole ratio, we have to convert to moles.
00:55
And to convert from grams to moles of magnesium, we need to use magnesium's molar mass from the periodic table.
01:03
All right, so we can convert from grams to moles that way.
01:08
Then we can convert from moles of magnesium to moles of hydrogen by using that mole ratio we just talked about, that one -to -one mole ratio from the balanced equation.
01:24
Finally, we can convert from moles of hydrogen to grams of hydrogen by using hydrogen's molar mass.
01:30
Notice it's h2, so we need to take two, two times the mass of hydrogen from the periodic table.
01:37
Okay, this is our plan.
01:38
Let's go ahead and set this up and solve it.
01:42
We have 6 .0 grams of magnesium...