a couple chem questions ..molar heat of a reaction and how much heat is released?

Question

okay, im having a lot of trouble figuring out the answer to these two questions. ive looked thru my book a number of times and can never find the exact help i need.

first question.
liquid hydrogen peroxide, an oxidizing agent in many rocket fuel mixtures, release oxygen gas on decomposition:
2H202(l) ----> 2h20(l)+o2(g) = -196.1kj

how much heat is released when 647 kg of h202 decomposes?

and the next question is
silver chloride agcl precipitates when solutions of silver nitrate, AgNO3, and sodium chlloride NaCl are mixed.

to determine the molar heat of reaction for this precipitation, 100.0ml of 0.400 M silver nitrate and 50.0mL of .800M sodium chloride were mixed in a constant-pressure calorimeter, which has a negligible heat capacity. the temp of the mixture rose from 21.15*C to 25.55*C. if the density of the solution is 1.0g/ml and its specific heat is 4.18j/g*c, what is the molar heat of reaction for this precipitation.

thanks. please show how to do them, soo ic an learn.

Answer 1

First question:

647,000gH2O2 x 1molH2O2/34gH2O2 x -196.1kJ/2molH2O2 = 1.86 x 10^6 kJ

Second question:

25.55C - 21.15 = 4.4degC difference Let thetotal solution be called S.

100.0mLAgNO3 x 0.400molAgNO3/1000mL = 0.040 mole AgNO3

50.0mLNaCl x 0.800molNaCl/1000mL = 0.040 mole NaCl

150mLS x 1gS/1mLS x 4.4degC x 4.18J/g-degC = 2759J

-2759J/0.040mol = -68970 J/mol = -69.0 kJ/mol to three sig figs.