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

In in , is to a 28.4-g (1-oz)−23.0 °c to −1.0 °c?

Kelly has come up with an explanation for why her sister is sometimes in a good mood and other times in a bad mood. she speculates that it is based on the hours of sleep her sister got the previous night. this explanation for her sister's behaviors is an example of a(n)

What mass of ca(oh)2 is needed to make 1250ml of a .75m solution?