Posted by **Sally** on Thursday, January 24, 2013 at 11:17am.

The neutralization of H3PO4 with KOH is exothermic.

H3PO4(aq) + 3KOH(aq) -> 3H2O(l) +K3PO4(aq) +173.2KJ

70.0 mL of 0.207 M H3PO4 is mixed with 70.0 mL of 0.620 M KOH initially at 21.87 °C. Predict the final temperature of the solution if its density is 1.13 g/mL and its specific heat is 3.78 J/(g·°C) Assume that the total volume is the sum of the individual volumes.

- Chemistry -
**DrBob222**, Thursday, January 24, 2013 at 3:09pm
You have 70.0mL x 0.207 M = 14.49 millimols which will use 43.47 mmols KOH.

You have 70.0mL x 0.620M = 43.4 mmols KOH. So the reaction will produce 43.4 mmols (0.0434 mols product) or

173,200 J/mol x 0.0434 = ? J.

?J = mass soln x specific heat soln x (Tfinal-Tinitial)

mass soln = (70mL+70mL)*1.13 g/mL

Solve for Tfinal.

- Chemistry -
**Sally**, Thursday, January 24, 2013 at 8:21pm
I got 7516.88J for ?J

and mass of soln = 158.2g

So my equation is

7516.88 J = 158.2g x 3.78 J/(g·°C)x(Tfinal -21.87)

12.57 = Tfinal - 21.87

Tfinal = 34.44°C

Which was wrong.

The hint they gave me was

Start by finding the amount of heat produced when 70.0 mL of 0.207 M H3PO4 react with 70.0 mL of 0.620 M KOH. Use the total volume and the density to find the mass. Then use the mass, m, heat, q, and specific heat, c, to find the change in temperature, ΔT.

Any idea as to what went wrong?

## Answer This Question

## Related Questions

- chemistry - A solution of 0.314M KOH is used to neutralize 10.0mL H3PO4 solution...
- chemistry - A solution of 0.314M KOH is used to neutralize 10.0mL H3PO4 solution...
- chemistry - A solution of 0.314M KOH is used to neutralize 10.0mL H3PO4 solution...
- Chemistry - A 11.0-mL sample of an unknown H3PO4 solution requires 116mL of 0....
- Chemistry - A solution of 0.316 M KOH is used to neutralize 16.0 mL H3PO4 ...
- chemistry - a 10.0mL sample of an unknown H3PO4 solution requirs 112mL of 0.100 ...
- chemistry - hello this is ellie again. I need help on this one problem A ...
- chemistry - A 10.0 mL sample of 3.00 M KOH(aq) is transferred to a 250.0 ml ...
- Chemistry - How many moles of potassium hydroxide are required to neutralize 1....
- chemistry - A 27.00 mL sample of an unknown H3PO4 solution is titrated with a 0....

More Related Questions