chemistry test next week...?

Question

and i need help on a question

when a 20g of sample of solid Pb(NO3)2 dissolves in 60g of water in a calorimeter, the temperature drops from 25 C to 20 C. calculate ΔH for the solution process.

Pb(NO3)2 (s) ---> Pb^2+ + 2 NO3 - (aq)

sorry can never type an equation on the net.

Answer 1

First, you need the specific heat of water (Cp=4.186 Joules/gram)

4.186*(25-20)*60g=total heat absorbed=1 255.8 Joules

20g / (82+2*(14+3*16))=00970873786 moles of lead nitrate

delH = total heat absorbed / total moles
= 1,255.8/0.09709 = 12 934 Joules/mol

Since the temperature drops it is an endothermic reaction.