Question

A stock solution is prepared by adding 20mL of 0.2M Na3PO4 to enough water to make 80mL. What is the Na+ concentration of 20mL of the stock solution?

I am thinking .012:
a) .02 times .2 = .004
b).004 times 3 = .012 (for each Na in the molecule)

Seems too simple

Answer 1

Yes and no. Yes, it's fairly simple; no 0.012 isn't right.

How much is the Na3PO4 diluted? It started at 0.2M so it is now
0.2M x (20 mL/80 mL) = ?M Na3PO4.
Then Na^+ is 3x that.

Answer 2

Write three equations (including ΔH values) that represent the heats of formation for each C6H12O6(s),
CO2(g), and H2O(l). (Hint: look up heats of formation for each participant)