Question

2) Consider the combustion reaction of ethylene at 25 °C and 1 bar, but in the case that H20 is produced as a gas rather than a liquid: C2Halg)+3 O2(g)>2 CO2(g) + 2 H20(g) What is the standard enthalpy of the reaction? Information that may be useful for the calculation is given below (at the same temperature and pressure): C2H4(g)3 O2(g) -»2 CO2(g)+ 2 H2O(liq) AtusH(H20) 6.008 kJ mol-; AvaphH°(H2O) = 44.016 kJ mol-; AtH°(H20,g) = -241.82 kJ mol- (A)-1410.0 kJ mol- (B)-1310.9 kJ mol~ (C)-1322.0 kJ m ol ~ (D)-1893.6 kJ mol -1 (E)-1416.0 kJ mol ~ (F) -1918.0 kJ m ol~ AcHo-1410.0 kJ mol-1

Answer 1

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Known reaction:

C2H4)302g2CO2(g) 2H20

Enthalpy change for this reaction is given by:

AcH 1410.0 kJ/mol

The negative sign indicates that the energy is released.

When the formed water in liquid form is converted into gas, some amount of this released energy will be used by water for phase change.

Given that, Enthalpy of vaporization of water,

44 kJ /mol AvapH

2 mol of water is formed, hence energy used by water is given by:

AH 2.AyapH° 2 mol x 44 kJ/mol +88 kJ

Therefore, standard enthalpy change for this reaction is given by:

CHA 302( 2CO2()2H2Og)

AH AcH+AH =-1410+88 kJ/mol

AH° 1322 kJ/mol

So the correct option is (C) -1322 kJ mol^-1

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