Carbon monoxide reacts with oxygen to form
carbon dioxide by the following reaction:
2CO(g) + O2(g) --> 2CO2(g)
�change in H for this reaction is −135.28 kcal.
If 811.7 kcal is released, how many moles of
CO must have reacted?
1. 16.3 mol
2. 40.5 mol
3. 12.0 mol
4. 5.41 mol
5. 6.00 mol
6. 1.35 mol
7. 270.5 mol
Didn't I do the Al2O3 for you? That should show you how to do it.
Basically, reword the question. 135 kcal are released when 2 mols CO are consumed. How may mols CO must be consumed to produce 811.7 kcal. That's
2 x (811.7/135.28) = ?
To find the number of moles of CO that reacted, we need to use the heat of reaction (∆H) and the amount of heat released (811.7 kcal).
From the balanced chemical equation:
2CO(g) + O2(g) -> 2CO2(g)
We can see that the stoichiometric ratio between CO and heat released is 2:1. This means that for every 2 moles of CO that react, 811.7 kcal of heat is released.
To calculate the number of moles of CO, use the ratio:
moles of CO = (811.7 kcal * 1 mol CO) / (∆H)
Substitute the given values:
moles of CO = (811.7 kcal * 1 mol CO) / (-135.28 kcal)
Calculating:
moles of CO = -811.7 kcal / 135.28 kcal/mol = -6.00 mol
Since moles cannot be negative, the correct answer is 6.00 mol of CO (Option 5).
To determine the number of moles of CO that must have reacted, we can use the concept of stoichiometry.
We can start by calculating the amount of heat (in kcal) released using the given value for the change in H and the balanced chemical equation:
ΔH = -135.28 kcal
Heat released = 811.7 kcal
Since the reaction is exothermic (heat is released), the value for the change in H is negative. Therefore, we can use the following equation to relate the amount of heat released to the number of moles of CO:
ΔH = (Heat released)/n, where n is the number of moles of CO
Rearranging the equation, we get:
n = (Heat released)/ΔH
Substituting the given values into the equation:
n = 811.7 kcal / (-135.28 kcal)
Calculating this expression yields n ≈ -6.00 mol.
However, the number of moles cannot be negative. Therefore, we take the absolute value of the result to obtain the number of moles:
n ≈ |-6.00| ≈ 6.00 mol
So, the correct answer is option 5: 6.00 mol.