1. QUESTION:
Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained mol N2, and now contains only mol N2 as a result of the reaction, how much H2 was consumed?
A mol, B mol, C mol
Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained mol N2, and now contains only mol N2 as a result of the reaction, how much H2 was consumed?
A mol, B mol, C mol
PAUSE
CLICK CONTINUED ON NEXT SLIDE

2. We can summarize this fact using the equation shown here.
QUESTION:
Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained mol N2, and now contains only mol N2 as a result of the reaction, how much H2 was consumed?
A mol, B mol, C mol n1 c1 = n2 c2
Amounts of reactants and products involved in a reaction are directly proportional. The mole-to-mole ratio is implied by the coefficients in the balanced equation.
The changes in the amounts of reactants and products involved in a reaction are directly proportional, and
the proportionality is implied by the coefficients in the balanced equation.
We can summarize this fact using the equation shown here.
If substances 1 and 2 are involved in a reaction
Then the ratio of the
change in moles of substance 1
HIGHLIGHT n1
to the change in moles of substance 2.
is equal to the ratio of
the coefficient of substance 1 in the balanced equation
HIGHLIGHT c1
to the coefficient of substance 2 in the balanced equation.
HIGHLIGHT c2
We can rearrange this equation to solve for moles of substance 1...
CLICK
CONTINUED ON NEXT SLIDE

3. QUESTION:
Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained mol N2, and now contains only mol N2 as a result of the reaction, how much H2 was consumed?
A mol, B mol, C mol n1 c1 = n2 c2 c1
And we get
n1 equals n2 times c1 over c2
BOX equation
Let’s see how we can apply this equation to the question we’re working on...
If you know the moles of a reactant consumed, or the moles of product produced.
Assign that to n2.
CALLOUT “Known”
Then, to figure out the corresponding change in moles of another substance,
HIGHLIGHT n1
Simply multiply n1 by a conversion factor based on the coefficients of substances 1 and 2.
HIGHLIGHT c1/c2
CALLOUT “ratio of coefficients” pointing to c1/c2
CLICK
CONTINUED ON NEXT SLIDE n1 n2 x = c2

4. QUESTION:
Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained mol N2, and now contains only mol N2 as a result of the reaction, how much H2 was consumed?
A mol, B mol, C mol
n2 = mol – mol = mol (N2) c1
CLICK
We’re given that the amount of nitrogen dropped from moles to moles.
Therefore, the change in the amount of nitrogen is moles minus equals
CLICK This is our n2.
We multiply it by a conversion factor
CLICK CLICK so that we can determine the amount of hydrogen consumed.
Since we’re interested in hydrogen, we put the coefficient of hydrogen in the numerator
CLICK The coefficient of hydrogen in the balanced equation is 3.
HIGHLIGHT 3 in balanced equation and 3 in numerator
... and put the coefficient of nitrogen in the denominator
CLICK The coefficient of N2 in the balanced equation is 1.
HIGHLIGHT 1 in balanced equation and 1 in denominator
The ratio of coefficients serves as a conversion factor.
SHOW CANCELLATION OF UNITS
An the answer we get here is moles of hydrogen.
Note that we keep three significant digits in our answer since the least precise term in our calculation, 0.300,
has only three significant digits. The numbers 3 and 1 in the conversion factor are exact.
Therefore, the correct answer is A.
CLICK PAUSE END RECORDING n1 n2 x = c2
3 mol H2
0.300 mol N2 = x
1 mol N2
= mol H2

5. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08