Question

40.0 mL of a 0.100 molar aqueous solution of silver nitrate (AgNO3) is mixed with 40.0 mL of a 0.100 molar aqueous hydrochloric acid solution (HCl) at 23.4 degrees Celsius in a coffee cup calorimeter. If the final temperature reached by the reaction is 26.4 degrees Celsius, calculate the enthalpy change for the reaction.

AgNO3 + HCl -> AgCl + HNO3

i know enthalpy change is q = m * c * Δt but it doesn't tell me the specific heat capacity. and if i'm supposed to find the surroundings enthalpy change first and it's water, then it didn't tell me how much water was there or anything?

Answer 1

Last time I solved a problem like this, the heat capacity of water was used since the reactants were are considerably diluted.

Answer 2

oh ok. 1 mL = 1g right?

Answer 3

q = 80g * 4.18 J/(°C x g) * 3°C
q = 1003.2 J

Answer 4

I think you should use the actual masses of the solutions.
You should really consult your textbook because I learned using the British system, which may be different.

Answer 5

i don't have a textbook because i'm doing this class online. and i only know that one formula for enthalpy change and it says m has to be in grams

Answer 6

Use the actual masses.

Answer 7

what do you mean? could you show me?

Answer 8

0.1M AgNO3 is 0.1*Molar Mass or AgNO3. Add that to the mass of the water it is diluted in.

Answer 9

That is 0.1*169.87g/mol = 16.987g. That's the mass of the AgNO3.
Then it is diluted with 40mL. So, 16.987+mass(40mL).