# Thermochemistry, heat calculation.

1. Jan 10, 2012

### AerospaceEng

1. The problem statement, all variables and given/known data

When 10.00 mL of a solution of strong acid is mixed with 100.00 mL of a solution of weak base in a coffee-cup calorimeter, the temperature rises from 22.8 oC to 26.8 oC. Determine q for the acid-base reaction, assuming that the liquids have densities of 1.00 g/mL and the same heat capacities as pure water.

2. Relevant equations

total volume V=110.0mL
change in temperature delta T = 4
mass m = 110.0g
heat capacity for water C=75.291J/(mol$\circ$C

q = nC$\Delta$T
q = mC$\Delta$T

3. The attempt at a solution

so I used the formula

q = mC$\Delta$T

because with the information given i couldn't find the number of moles and because only the molar heat capacity is given to use i had to find the mass based heat capacity and I found it to be C = 4181.3J/KgK

and then found q = 460J

which then the computer told me it was wrong.

It seemed odd that i had to go find the heat capacity rather than use the one provided. So I feel already there's my first mistake. But i know the formula is right so I can't see why it wouldn't work. However clearly my chemistry isn't that strong so perhaps I'm missing something. Any guidance would be appreciated! Thanks

2. Jan 18, 2012

### ehild

How did you get 460 J for q=mcΔT when m=0.11 kg, ΔT=4 and c=4181.3 J/kgK?

ehild