# Heat of reaction

#### dg_5021

In the reaction shown below, 699 kcal of heat are liberated when 2.10 g of AgNO3 reacts with HCL:
AgNO3(aq) + HCL(aq) = AgCl(s) + HNO3(aq)
What is the heat of reaction in terms of kcal/mole of AgNO3?

How do u do this problem? Is there a formula for it?

#### chem_tr

Gold Member
I am surprised how you didn't see this, but it's no problem since you try to learn something and asked this question.

Okay, 2.10 grams of AgNO3 give 699 kcal of thermal energy (heat), right? Then solve a simple proportion, like "2.10 grams give 699 kcal, then one mole of AgNO3 gives that". Remember that you can use 107.8, 14.0, and 16.0 g/mol for silver, nitrogen, and oxygen respectively, to find how many grams of AgNO3 are there in one mole of compound.

If there is another point you haven't understood yet, don't hesitate to ask.

Take care.

#### dg_5021

what i did was divide (699kcal /2.10g AgNo3) x (169.91 g AgNo3/ 1mol AgNo3) = 56555.8 kcal/mole of AgNo3

is this correct?

#### chem_tr

Gold Member
It seems to be correct. Unit analysis gives the same result.

#### dg_5021

thanks for the help

#### gravenewworld

Do you mean what is the Heat of formation of AgNO3?
If this is the question then, turn 2.1 g of AgNO3 into moles. THen for the reaction, the the heat of the reaction is= sum(moles x H of formation of products)-sum(moles x H of formation of reactants). You should have a table of thermodynamic data in the back of you text with the heats of formation for everything except maybe AgNO3 which is what you are trying to find. You are given the heat of the reaction so just solve the equation for the heat of formation of AgNO3.

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