# Homework Help: Delta H for 25.0 g NaOH in 100ml of 31.5% HCl

1. Jan 23, 2010

### Jan Hill

1. The problem statement, all variables and given/known data
How do I calculate delta H given the above info and knowing the specific heat capacity of
H2O and that the change in temperature when the 2 react is 6.2 degrees C

2. Relevant equations

3. The attempt at a solution

Using Q = mcdeltatheta where
m=mass and
c=specific heat capacity of H2O (Using H2O's specific heat capacity because there is an aqueous environment here)
delta T - 6.2 degrees C
Finding Q then substituting in for deltaH = m x delta T x Q
Is this the right way to go about finding delta H for this problem?

2. Jan 24, 2010

### Staff: Mentor

Yes and no. Yes - that's the corect approach. No - assumption that you should use specific heat of water is in general wrong, as it works reasonably well for diluted solutions, 31.5% HCl is not diluted (10M), adding 25.0 g of NaOH won't dilute it much. But if you have no access to tables of specific heat as a function of solution concentration, this assumption is better than nothing.

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3. Jan 24, 2010

### Jan Hill

Thank you

4. Jan 24, 2010

### Jan Hill

Re: delta H for 100ml of 1.0 mol/L HCl with 100ml. of 1.0 mol/L NaOH

In this case, mixing 2 aqueous solutions, how would I calculate delta H without a value for mass?

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