How much heat in kilojoules is evolved in converting 2.00 mol of steam at 150 ∘c to ice at -55.0 ∘c? the heat capacity of steam is 1.84 j/g∘c and that of ice is 2.09 j/g∘c.
remember that if heat is leaving the system, then q is a negative number and if heat is entering the system, then q is a positive number.

= 115.898 kJ

Explanation:

Heat evolved in converting 2.00 mol of steam at 150 ∘C to ice at -55.0 ∘C

Will be calculated in steps

Step 1; Heat evolved by steam from 150°C to 100°C

Heat = (2×18) g × 1.84 J/g°C × (150 -100)

       = 3312 Joules

Step 2; Heat required to convert steam to water without change in temperature;

Heat = moles × Molar Latent heat of vaporization.

        =  2 moles × 4.07 ✕ 104 J/mol

        = 8.14 × 10^4 Joules

Step 3: Heat evolved by water  from 100°C to 0°C.

Heat = mass × specific heat capacity × ΔT

        = (2 × 18) × 4.18 J/g°C × 100

        = 15,048 Joules

Step 4; Heat evolved in converting water at 0°C to ice at 0°

Heat = number of moles × molar latent heat of fusion

        = 2 moles × 6000 j/mole

        = 12 000 Joules

Step 5, heat evolved in converting ice at 0°C to -55°C

Heat = mass × specific heat capacity × ΔT

        = (2×18) × 2.09 j/g°C × 55

        = 4138.2 Joules

Total amount of heat evolved;

= 3312 J +  8.14 × 10^4 J + 15,048 J + 12 000 J +  4138.2 J

= 115,898.2 joules

= 115.898 kJ