Given overall reaction: P4 + 10Cl2 ---> 4PCl5 Delta H for the reaction = ?
PCl5 -----> PCl3 + Cl2 Delta H = +157 kJ
P4 + 6Cl2 ----> 4PCl3 Delta H = -1207 kJ
Calculate the Delta H for the overall reaction.
P4+10Cl2>>4PCl3 + 4 Cl2 H=-1207kJ
4PCl3+4Cl2>>4PCl5 H=-157*4 kJ
total? add the two H
Well, it looks like we have a chemical circus going on here! Let's break it down and put on our chemistry clown noses.
First, we have the reaction PCl5 → PCl3 + Cl2 with a ΔH of +157 kJ. But wait! We need to balance the equation to make sure all our clowns are on the same page. So, we'll multiply PCl5 by 4 to match the number of PCl3 and Cl2.
4PCl5 → 4PCl3 + 4Cl2
Next, we have the reaction P4 + 6Cl2 → 4PCl3 with a ΔH of -1207 kJ. Again, let's balance the equation so all our circus performers are accounted for.
P4 + 6Cl2 → 4PCl3
Now, let's add the two reactions together, cancel out the common clowns, and see what we get.
4PCl5 + P4 + 6Cl2 → 4PCl3 + 4PCl3 + 4Cl2
Simplifying a bit,
4PCl5 + P4 + 6Cl2 → 8PCl3 + 4Cl2
Finally, let's sum up the ΔH values for each reaction:
ΔH(overall) = 4(ΔH(PCl5 → PCl3 + Cl2)) + ΔH(P4 + 6Cl2 → 4PCl3)
ΔH(overall) = 4(157 kJ) + (-1207 kJ)
ΔH(overall) = 628 kJ - 1207 kJ
ΔH(overall) = -579 kJ
So, the delta H for the overall reaction is -579 kJ. And that, my friend, is how the chemical circus performs its heat show!
To calculate the delta H for the overall reaction, we can use Hess's Law, which states that the enthalpy change of a reaction is independent of the pathway taken.
By manipulating the given reactions, we can derive the overall reaction:
P4 + 6Cl2 ----> 4PCl3 (1)
4PCl3 ----> 4PCl3 + 4Cl2 (2)
2PCl3 + 3Cl2 ----> 2PCl5 (3)
To obtain the desired reaction:
P4 + 10Cl2 ----> 4PCl5
We can add the given equations (1), (2), and (3) as follows:
P4 + 6Cl2 + 4PCl3 ----> 4PCl3 + 4Cl2 + 2PCl3 + 3Cl2 ----> 4PCl5
Simplifying the equation, we get:
P4 + 10Cl2 ----> 4PCl5
Now, we need to sum up the delta H values of the individual reactions to obtain the overall delta H:
Delta H (overall) = Delta H (1) + Delta H (2) + Delta H (3)
Delta H (overall) = -1207 kJ + 0 kJ + 157 kJ
Therefore, the delta H for the overall reaction is:
Delta H (overall) = -1207 kJ + 0 kJ + 157 kJ = -1050 kJ
To calculate the overall delta H for the given reaction, we can use the concept of Hess's law. According to Hess's law, the overall delta H for a reaction can be determined by the summation of the delta H values for the individual reactions that make up the overall reaction.
In this case, we have two individual reactions with their respective delta H values:
1. PCl5 → PCl3 + Cl2 (delta H = +157 kJ)
2. P4 + 6Cl2 → 4PCl3 (delta H = -1207 kJ)
To obtain the overall delta H, we need to manipulate the second reaction to match the reactants and products of the first reaction, so that we can cancel out PCl3 and Cl2 to get just PCl5.
To do this, we multiply the second reaction by 4, so that the coefficients of PCl3 in both reactions will be equal and we can cancel them out:
4(P4 + 6Cl2 → 4PCl3) --> 4P4 + 24Cl2 → 16PCl3
Now, let's sum up the two reactions:
(PCl5 → PCl3 + Cl2) + (4P4 + 24Cl2 → 16PCl3)
When we add these reactions together, the PCl3 and Cl2 terms cancel out:
P4 + 10Cl2 → PCl5 + 16PCl3
Now, we can see that the overall reaction is:
P4 + 10Cl2 → PCl5
To calculate the overall delta H, we sum up the delta H values of the individual reactions:
Delta H overall = Delta H1 + Delta H2
Delta H overall = +157 kJ + (-1207 kJ)
= -1050 kJ
Therefore, the overall delta H for the reaction P4 + 10Cl2 → 4PCl5 is -1050 kJ.