[F.5]Chem enthalpy change

1.Consider the following reaction:
2N2H4(l)+N2O4(l)+3N2(g)+4H2O(g) △H = -1078kJ

How much heat is released by the reaction during the formation of 14.0g of
N2(g)? (relative atomic mass:N=14.0)

A . 1078kJ
B . 1797kJ
C . 3234kJ
D . 5390kJ

2.Consider the following reaction:
4Li(s)+O2(g)->2Li2O(s) △H = -1198kJ

What mass of Li should be reacted with excess O2(g)in order to release 551kJ of heat?(relative atomic mass:Li=6.9)

A.0.667g
B.3.75g
C.12.7g
D.60.0g

3.The first step in the industrial recovery of zinc from zinc sulphide ore is roasting.Zince sulphide is converted to zinc oxide according to the following equation:
2ZnS(s)+3O2(g)->2ZnO(s)+2SO2(g) △H = -879kJ
(relative atomic mass:S=32.1,Zn=65.4)

For each gram of zinc sulphide roasted,
A.9.02kJ of heat are taken in.
B.9.02kJ of heat are released.
C.4.51kJ of heat are released.
D.4.51kJ of heat are taken in.

4.Consider the following equation and the associated value for △H :

2H2(g)+2Cl(g)->4HCl(g) △H =-92.3kJ

Which of the following statements about this information are correct?

(1)If the equation is reversed,the △H value equals +92.3 kJ.
(2)The four HCl bonds are stronger the four bonds in H2 and Cl2.
(3)23.1kJ of heat will be released when 1mole of HCl(g) is produced.

A.(1)and(2)only
B.(1)and(3)only
C.(2)and(3)only
D.(1),(2)and(3)


Please show steps....and tell me why.Thank you