Hello Today we'll be talking about Chapter 15 Question 94 which asks us to consider the net reaction generically shown at the top to a plus B to C three goes to two B plus A to C three. Now we need to calculate Delta H for this reaction using the two sub reactions shown A and B. So let's look att equation a first to a plus three have C two goes to A to C three, and the important thing to note is that we have to A and A to C three, and they match up well with the net equation there on the right side of the equation, the correct sides of the equation. So we don't need to do anything to equation a equation. Be to be plus three have C two goes to B to C three also has B to C three and to be, but now they're on the incorrect sites there on the flip sides of the equation from what we need.
So let's just rewrite this equation to be to have you be to see three and be on the correct side of the equation that we want. B to C three goes to to be plus three halves See, too, because we reverse the direction of this reaction. We just have to put a negative sign in front of the Delta H reaction. Negative to 85 Killer Jules now, And I'm gonna cross out the middle line now. So now we have to be to see three on the left side of the equation here and in the net reaction and be on the right side.
This means that we can combine sub equations A and B the reverse version of be here and hopefully some them to get the net reaction and also to get the Delta H reaction. And if we look, we have three have C two after the arrow on the bottom equation, and three have C two before the arrow on the top equation, which means we can cancel both of them out. And that leaves us with the net equation to a plus B to C three shown here goes to to be plus A to C three. We've generated the net reaction by just adding these two equations. And so because that worked, we can just add the delta H reactions as well.
And so we just have negative. 1874. Kill it, Jules. Plus negative 285 Killer Jewel's to give us the Delta H for the total reaction, which is equal to negative 2159. Killer Jules.
And so we can see that we can take Delta H is of known sub reactions and just combine them by reorganizing them, reversing the directions and changing the Delta h reaction slightly and then some them all together to get the Delta age for some net reaction. Thank you..