Question

2) The heat of fusion of ice is 333 J/g. For the process H2O(s) + H2O(1) Determine: a) AH b) AGⓇ at 0°C d) AG at -20°C e) AGⓇ at +20°C c) AS

Answer 1

(2) Write the reacti on as foll ows H20(s) H20() 1mole of solidice changes into 1mole of liquid water The change of phase of a substance from solid to li qui d at constant temperature is known as fusion Temperature, T = 0°C= 0+273 K = 273K Heat of fusi on, AH = 333 J/g (a) Enthalpy of the reaction is equal to the heat of fusi on ДН 3D ДН J 18.0 g AH° = 333x mol J AH5994 1kJ X mol 1000 J AH 6.0kJ/mol Therefore, the required solution is 6.0 kJ/mol or 333 J/g (c) Entropy of the reaction is as follows ДН ASo = - т 333 Jgx 18.0g ASO 273 K mol J ASo 22.0 mol K ASo 22.0 J/molK Therefore, the required soluti on is-22.0 J/molK (b) Write the expressi on for AG as follows A- ДН° -ТAS" Substitute the correspodning valuesin the above equati on and cal culate AG. AG 6.0 kJ/mol-(273K)(-22.0 J/molK) AG = 6.0kJ/mol+6.0kJ/mol AGo 12.0kJ/mol Therefore, the required solution is 12.0kJ/mol

(d) Temperature, T = -20 °C 20+ 273 K = 253 K Assuming AHo and AS does not change Write the expressi on for AG as follows AG = AH -TAS Substitute the correspodning valuesin the above equati on and calculate AG 1kJ AGo 6.0kJ/mol - (253 K) (-22.0 J/m olK)x; 1000 J AG 6.0kJ/mol 5.6kJ/mol AG 11.6 kJmol Therefore, the required solution is |11.6 kJ/mol (e) Temperature, T = +20 °C= +20+ 273 K 293K Assuming AHo and AS does not change Write the expressi on for AG as follows: AG ДН" -ТS® Substitute the correspodning valuesin the above equati on and calculate AG 1kJ 6.0kJ/mol - (293 K) (-22.0 J/m olK)x- 1000 J AG AG 6.0kJ/mol 6.45kJ/mol AG 12.45 kJ/mol Therefore, the required solution is 12.45 kJ/mol