Hello there.
The answer here is true. Cold objects melt faster in hot water than cold water.
2Al(s) + 3Cl₂ → 2AlCl₃
Forming the equation:
2(28) + 3(223) = ΔH + 2(111)
ΔH = 503 kJ
Writing this outside of the reaction equation:
ΔH = -503 kJ
2 - PE of products-PE of reactants.
You are trying to calculate the energy change that occurred from the start of the reaction (the reactants going in) to the end of the reaction (the products coming out). Therefore if there is more energy at the end, you will get a positive result from subtracting the PE of the reactants, and vice versa.
