I have worked this problem out, and I need help figuring out what I am doing wrong. Chem Help?

Question

A reaction like the one we will observe today was carried out in a very efficient calorimeter (assume its heat capacity to be zero). A sample consisting of acid and base with a total mass of 98.0 grams gave a temperature rise of 3.52 oC. The number of moles of acid and base was 0.241 (equal moles of each component). What is the heat of neutralization per mole of acid (or base)?

I DO NOT want the answer. I need to know how you figure it out. I have tried various ways. I think i go wrong with the moles. Do i need use the moles of water formed or the solution? If so, how? The specific heat for the solutions is 4.10.

Answer 1

I'm a little rusty in P. Chem, but I think it would go like this:

First, figure out the amount of heat generated. Now, the specific heat of the solution is 4.10. You really should give units, but I'm guessing this is J*g^-1*K^-1. In other words, it takes 4.1 joules of heat to raise the temperature of one gram of solution one Kelvin. Now in fact, you raised 98 grams of solution 3.52 K (a K and a oC are the same size). So you multiply the grams * the temperature rise * the specific heat = 98*3.52*4.10 = 1414.336 J, or 1.4 kJ after rounding.

Then, figure out the number of moles. That's easy in this case, it's given to you: 0.241 moles.

Finally, the molar heat of neutralization is equal to the total heat released (1.4 kJ) divided by the number of moles which produced it (0.241), making it equal to 5.8 kJ/mol.

I know you wanted the process, not the answer, but it's difficult for me to give one without the other.

Answer 2

It's the moles of equation as written, which is usually means one mole of everything.

I suspect that the moles (or the mass being heated) is given wrongly, because the "standard" answer is 57 or 58kJ/mol.

Check the exact wording of the question, and see if you are a factor of 10 out somewhere.