Science Buddies: "Ask an Expert"

So I am trying to make a cold pack for a science experment, using the following molecules, how much of each reactive is needed (in litters) to make the temperture drop from 25 to 5 degrees celsius?

2HCl(aq)+Na2OOCOO(aq)→2NaCl(aq)+HOOCOOH(s)

The heat of formations are as follows (in KJ/mol, and c= 1mol/L for liquids)

HCl:-167
Na2OOCOO: -1307
NaCl:-407
HOOCOOH: -827

Thanks in advance, Rémi Choquette

Hi,

From the temperature difference (-20 deg. C) you can figure out how much energy (kJ) is needed.

Then follow this example to figure out how much energy you get:

http://chemwiki.ucdavis.edu/Physical_Ch ... _Formation

Good luck