Two chemistry questions help. 10 points?

[Elizabeth T]

1.Explain the three MAIN diferences between a risk assessment and a risk perception.


2. a. H2(g) + 1/2 O2(g) --> H2O(l) ?H° f = -285.8 kJ
b. N2O5(g) + H2O(l) --> 2 HNO3(l) ?H°r = -76.6 kJ
c. 1/2 N2(g) + 3/2 O2(g) + 1/2 H2(g) --> HNO3(l)
?H°f=-174.1kJ

Calculate the ?H°, for the following reaction: 2 N2(g) + 5 O2(g) --> 2 N2O5(g).
show how you MANIPULATE your information equations to achieve your answer
(Show the formula's you used to please)