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

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





N2(g)+2H2(g)----%26gt; N2H4 (1)





Use the following:





H2(g) + 1/2O2(g) ----%26gt; H2O (g) -------- H= -242 kJ/mol





N2(g) + 2H2O ------- %26gt; N2H4(1) + O2 -------- H= +534 kJ/mol








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





CH4(g) + 2O2 -----%26gt; CO2(g) + 2H2O (l)





Use the following:





C(s) + 2H2(g) -----%26gt; CH4(g) -----------H= -74.8 kJ/mol





C(s) + O2(g) --------%26gt; CO2(g) -----------H= -393.5 kJ/mol





H2(g) + 1/2O2(g) ---------%26gt; 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)--------%26gt; MnO2(s)





Use the following:





MnO2(s) + Mn(s) --------%26gt; 2MnO(s)------------H= -240kJ/mol





2MnO2(s) ----------%26gt; 2MnO(s) + O2(g) ---------- H= +264 kJ/mol

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