00:02
There in this question we are given this balanced chemical equation.
00:06
I have omitted the states of matter because they are not going to be used in this problem.
00:12
So quite frankly, they're just in the way.
00:14
So i've omitted those.
00:15
What we know is we're trying to produce 1 .80 grams of water and we want to know how many grams of hydrogen we would need to do that.
00:27
Therefore, we're trying to convert from the mass of one substance in the equation to the mass of another substance in the equation, making this a mass -to -mass stoichiometry problem.
00:41
Stoichiometry is just the series of steps that allows us to convert from information about one thing in a problem to information about something else.
00:49
So let's look here.
00:50
It's going to take us three steps to convert from our starting point to our answer.
00:55
In our first step, we're going to convert from grams of h2o to moles of h2o.
01:00
And we do that by using the molar mass of h2o.
01:07
That's the mass of one mole of the substance in grams and we get that from the periodic table by adding together the mass of two hydrogen and one oxygen.
01:17
All right, after that we're going to convert from moles of h2o to moles of h2o.
01:23
And we'll do that by using the mole ratio from the balanced equation.
01:29
The mole ratio comes to us from the coefficients in the equation.
01:33
So they show us that for every two moles of h2o that we want to produce, we need to start with two moles of hydrogen.
01:40
So this would be a two to two mole ratio.
01:43
And then in our final step, we need to convert from moles of h2 to grams of h2 by using h2's molar mass.
01:53
All right, so let's go ahead and set this up and solve for our answer...