Question

1.) To calculate the enthalpy of the reaction, H2 (g) + Cl2 (g) → 2HCl (g), you need to subtract which heats of formation?

a. HCl (g) and H2 (g)
b. HCl (g)
c. H2 (g) and Cl2 (g)
d. none of them

2.) When calculating the enthalpy of a reaction, if the reactant has a coefficient of 2, what must be done to the ΔHf value of the reactant?

a. Divide by 2
b. Multiply by 2
c. Add 2
d. Subtract 2

3.) If the reaction is reversed during a Hess’s law calculation, what must be done to the ΔH for that reaction?

a. It must be left alone
b. It must be multiplied by 1
c. The sign must change
d. the sign must not change

Answer 1

Any guesses?

Answer 2

@taramgrant0543664 not at all lol im taking a class with JUST tests and quizzes and no lessons or anything

Answer 3

Ok well delta Hf is found by products minus reactants

Answer 4

So for number 1 there you are looking for the reactants

Answer 5

@taramgrant0543664 so would it be B. HCl (g)?

Answer 6

HCl is the product of the reaction the reactants are the things that form the products

Answer 7

@taramgrant0543664 oh so wait it would actually be C?

Answer 8

Yes it would be

Answer 9

Any guesses for the second one?

Answer 10

@taramgrant0543664 for the second one im guessing it would be add 2 but am not sure

Answer 11

No it would not be add two. There are twice the amount of reactants so Hf should be twice the amount

Answer 12

@taramgrant0543664 ohhh so multiply 2!

Answer 13

Yes it would be

Answer 14

For the last one since you are reversing the reaction so essentially you are flipping it any idea what it could be?

Answer 15

Flipping is the key word there

Answer 16

@twelveroses i have to go now but do you have an idea on what it is?

Answer 17

@taramgrant0543664 no i dont im trying to figure out what the formula is for hess's law calculations :/

Answer 18

You don't need the formula for the question but all it is is delta Hf equals the sum of heats for the products minus the sum of heats for the reactants

Answer 19

For number three if you are going in the positive direction and you reverse the reaction you're going to be going in the negative direction now. I'm sorry I have to go now though!!

Answer 20

its okay thank you!!