# Homework Help: Acid & Base reaction?

1. Feb 6, 2010

### Glen Maverick

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

NaOH(aq) + HCl(aq) ------> NaCl(aq) + H2O(l)

50mL of 1.0M HCl and 50ml 1.0M NaOH was mixed. Total heat is 2826J. If the density of 0.5M NaCl produced in this reaction is 1.02g/mL:
a) What is the mass of the solution?
b) Moles of water formed
c) Moles of NaCl formed
d) Molar heat of reaction

2. Relevant equations

3. The attempt at a solution

a) 1.02g/ml x 100ml = 102 g
b) 50ml x 0.001 x 1M =0.05 moles of Water
d) 2826/0.05 = 56.52kJ

Iam very confused about c). Why is there "0.5M"in the question? Do I have to use that molarity during calculation?

2. Feb 7, 2010

### Staff: Mentor

I am not sure what is so confusing? If you start with amounts of reagents given, you calculate number of moles of NaCl produced, and you check what is the final volume, you will find 0.5 M is just the final concentration of NaCl. I suppose teacher will prefer you to calculate amount of product from the stoichiometry, not from the final concentration, but both ways give correct result.

Last edited by a moderator: Aug 13, 2013
3. Feb 7, 2010

### Glen Maverick

I get it. :) What I am also confused about is whether the mass of the solution os 102g or 100g. TA said we ar multiplying the dnesity of NaCl to 100ml(50ml+50ml) for finding heat gained by solution. according to the lab manual, the calculation is saying 102 g. However, I think 100g is the mass of the solution.

Last edited: Feb 7, 2010
4. Feb 7, 2010

### Staff: Mentor

What volume? What density? What mass then?

Last edited by a moderator: Aug 13, 2013