Based on the enthalpy changes given for the reactions, which reactions are endothermic?

2H2O → 2H2 + O2, ΔH = 484 kJ
C + O2 → CO2, ΔH = -394 kJ
H2 + Br2 → 2HBr, ΔH = -73 kJ
2NH3 → N2 + 3H2, ΔH = 92 kJ

At a certain temperature the rate of this reaction is first order in hi with a rate constant of : 0.0632s2hig=h2g+i2g suppose a vessel contains hi at a concentration of 1.28m . calculate how long it takes for the concentration of hi to decrease to 17.0% of its initial value. you may assume no other reaction is important. round your answer to 2 significant digits.