Calculate ΔHrxn for the following reaction:
C(s)+H2O(g)→CO(g)+H2(g)
Use the following reactions and given ΔH values:
C(s)+O2(g)→CO2(g), ΔH= -393.5 kJ
2CO(g)+O2(g)→2CO2(g), ΔH= -566.0 kJ
2H2(g)+O2(g)→2H2O(g), ΔH= -483.6 kJ
Well, let's see what we can do here! To find the ΔHrxn for the given reaction, we can break it down into a series of known reactions with known ΔH values.
First, let's start by getting the desired reaction from the given reactions. We can double the first reaction to get:
2C(s) + 2H2O(g) → 2CO(g) + 2H2(g)
Now, let's take a look at the given reactions and try to match them up with the required reaction. We can reverse the first reaction to get:
CO2(g) → C(s) + O2(g)
ΔH = 393.5 kJ
Multiplying the second reaction by 2, we get:
4CO(g) + 2O2(g) → 4CO2(g)
ΔH = -1132.0 kJ
Multiplying the third reaction by 2, we get:
4H2(g) + 2O2(g) → 4H2O(g)
ΔH = -967.2 kJ
Now, let's rearrange these reactions and try to add them up to get the desired reaction:
4C(s) + 4H2O(g) → 4CO2(g) + 4H2(g)
ΔH = 4 * -393.5 kJ = -1574.0 kJ
Next, we'll cancel out the common compounds on both sides to get the final reaction:
C(s) + H2O(g) → CO(g) + H2(g)
ΔHrxn = -1574.0 kJ / 4 = -393.5 kJ
So, ΔHrxn for the given reaction is -393.5 kJ.
Hey, did you know that chemists like to make these reactions as complicated as possible just to keep us on our toes? Can't blame them, though. Keeps things interesting!
To calculate the enthalpy change (ΔHrxn) for the given reaction, we can use Hess's Law. Hess's Law states that the overall enthalpy change of a reaction is equal to the sum of the enthalpy changes of the individual steps in the reaction.
Step 1: Multiply the first reaction by 2 to match the coefficient of CO2 in the desired reaction:
2C(s) + 2O2(g) → 2CO2(g) ΔH = 2(-393.5 kJ) = -787.0 kJ
Step 2: Reverse the second reaction and multiply it by 2 to match the coefficient of CO in the desired reaction:
-2CO2(g) → -2CO(g) + O2(g) ΔH = -2(-566.0 kJ) = 1132.0 kJ
Step 3: Reverse the third reaction and multiply it by 2 to match the coefficient of H2O in the desired reaction:
-2H2O(g) → -4H2(g) - 2O2(g) ΔH = -2(-483.6 kJ) = 967.2 kJ
Step 4: Sum up the enthalpy changes from the above steps to calculate the overall enthalpy change of the reaction:
ΔHrxn = -787.0 kJ + 1132.0 kJ + 967.2 kJ
= 312.2 kJ
Therefore, the ΔHrxn for the reaction C(s) + H2O(g) → CO(g) + H2(g) is 312.2 kJ.
To calculate ΔHrxn for the given reaction, we need to use Hess's law, which states that if a reaction can be expressed as the sum of two or more other reactions, then the ΔH for the overall reaction is the sum of the ΔH values of the individual reactions.
Let's break down the given reaction into simpler reactions and use the given ΔH values to calculate ΔHrxn.
1. Multiply the first reaction by 2 to match the coefficient of CO in the desired reaction:
2C(s) + 2O2(g) → 2CO2(g) (multiply ΔH by 2)
ΔH1 = -2(393.5 kJ) = -787.0 kJ
2. Multiply the second reaction by 1/2 to match the coefficient of CO in the desired reaction:
CO(g) + 1/2O2(g) → CO2(g) (multiply ΔH by 1/2)
ΔH2 = 1/2(-566.0 kJ) = -283.0 kJ
3. Multiply the third reaction by 1/2 to match the coefficient of H2O in the desired reaction:
H2(g) + 1/2O2(g) → H2O(g) (multiply ΔH by 1/2)
ΔH3 = 1/2(-483.6 kJ) = -241.8 kJ
Now, we can add the individual reactions together to get the desired reaction:
2C(s) + 2O2(g) + 2H2(g) + 1/2O2(g) → 2CO(g) + 2H2O(g)
To cancel out the common species on both sides (2O2(g)), we subtract the second and third reaction from the first reaction:
ΔHrxn = ΔH1 - ΔH2 - ΔH3
= -787.0 kJ - (-283.0 kJ) - (-241.8 kJ)
= -787.0 kJ + 283.0 kJ - 241.8 kJ
= -745.8 kJ
Therefore, ΔHrxn for the given reaction C(s) + H2O(g) → CO(g) + H2(g) is -745.8 kJ.