Please help me!! It's due on tomorrow - chemistry?

1. What is the enthalpy change for the following reaction?

N2(g)+2H2(g)----> N2H4 (1)

Use the following:

H2(g) + 1/2O2(g) ----> H2O (g) -------- H= -242 kJ/mol

N2(g) + 2H2O ------- > N2H4(1) + O2 -------- H= +534 kJ/mol


2. What is the enthalpy change for the following reaction?

CH4(g) + 2O2 -----> CO2(g) + 2H2O (l)

Use the following:

C(s) + 2H2(g) -----> CH4(g) -----------H= -74.8 kJ/mol

C(s) + O2(g) --------> CO2(g) -----------H= -393.5 kJ/mol

H2(g) + 1/2O2(g) ---------> H2O(l) ------------H=-235.8 kJ/mol


3. Calculate the amount of heat needed to melt 35.0g of ice at 0°C. Express your answer in kilojoules.


4. What is the enthalpy change for the following reaction?

Mn(s)+O2(g)--------> MnO2(s)

Use the following:

MnO2(s) + Mn(s) --------> 2MnO(s)------------H= -240kJ/mol

2MnO2(s) ----------> 2MnO(s) + O2(g) ---------- H= +264 kJ/mol

Answer:
1. 2(-242) + (534) = 50kJ
2. -(-74.8) + (-393.5) + 2(-235.8) = -790.3kJ
3. 35.0g x 335.5 kJ/kg = 11.74 kJ
4. (-240) + -1/2(264) = -372 kJ

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