Question

Calculate the energy, q, needed to vaporize 1 mole of water at the boiling point.

Calculate the energy, q, needed to melt 1 mole of ice.

Calculate the energy, q, needed to completely break apart 1 mole of water into hydrogen and oxygen atoms.

Answer 1

delta H vap od water = 40.65 KJ/mol

So heat required to vapourize 1 mol of water = 49.65 KJ

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Heat of fusion of ice = 334.774 J/g

molar mass of ice (H2O) = 18 g

Q= 334.774*18 =6030 J = 6.03 KJ

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H2O is formed from H2 and O2

H2 + 1/2 O2 ---> H2O

delta H = delta Hf (H2O) - delta Hf (H2) - 0.5 * delta Hf (O2)

                = 40.65 KJ/mol -0 - 0

                = 40.65 KJ/mol

for 1 mol,

Q= 40.65 KJ