# Problem: Write a balanced equation and draw an enthalpy diagram for (select if exothermic or endothermic):combustion of one mole of methanevaporization of liquid alcoholfreezing of liquid waterformation of 1 mole of potassium chloride from its elements (heat is released)

###### FREE Expert Solution

Exothermic reactions

▪ lose energy, releases heat, temperature of the surroundings increases
▪ involves bond formation (for phase change: gas → liquid → solid)
▪ ΔH is negative

Endothermic reactions

▪ gain/requires energy, absorbs heat, temperature of the surroundings decreases
▪ involves breaking bonds (for phase change: solid → liquid → gas)
▪ ΔH is positive

• combustion of one mole of methane

Reaction:      CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)

▪ releases heat:   exothermic • vaporization of liquid alcohol

*generic form of alcohol: R‒OH

Reaction:      R‒OH(l) → R‒OH(g)

▪ phase change (liquid → gas):    endothermic • freezing of liquid water

Reaction:      H2O(l) → H2O(s) ###### Problem Details

Write a balanced equation and draw an enthalpy diagram for (select if exothermic or endothermic):

combustion of one mole of methane

vaporization of liquid alcohol

freezing of liquid water

formation of 1 mole of potassium chloride from its elements (heat is released)