# Calorimetry Problem

1. Dec 7, 2006

### jxs919

lemme start off with the problem:

15.3g of NaNO3 were disssolved in 100 g of water in a calorimeter. The temperature of the water dropped from 25 C to 21.56 C. Calculate delta H for the solution process

here's what i figure:

delta H = q

q = MCT

M = mass of water

C = specific heat of water

T = change in temp

so plug and chug should get me my answer ?

i dunno why but i think i need to incorporate the mass of my NaNO3 somewhere...

2. Dec 8, 2006

### Gokul43201

Staff Emeritus
1. This question belongs in the homework & coursework subforum.

2. $$\Delta H = \Delta (mCT) = m_fC_fT_f - m_i C_iT_i$$
where f:final, i:initial

3. Dec 8, 2006

### jxs919

uhm thanks for the formula but i'm still lost

is the massfinal.. water + substance ?

and the C final.. how do i calculate that ? i only know the specific heat of water by itself

4. Dec 8, 2006

### Gokul43201

Staff Emeritus
Correct.

I guess a reasonable approximation might be to use C(final) = C(initial) = C(water).

If you want to be more accurate, you can look up specific heats of solutions in a chemistry handbook like Lange or CRC (my guess is that you don't have to).

5. Dec 9, 2006

### GCT

The experimental solution to this problem would need to incorporate the specific heat capacity of the calorimeter. Yes, you need to incorporate the mass of NaNO3 and the water to find the enthalpy in terms of, let's say, kJ/"____" for the dissolution process.