EASY
Diploma
IMPORTANT
Earn 100

Predict whether the following reactions will have a positive or negative entropy change, S.

NH4NO3(s)  N2O(g) + 2H2O(g)

Give answer as either positive or negative.

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Important Questions on Energetics and Thermochemistry (AHL)

EASY
Diploma
IMPORTANT

Predict whether the following reactions will have a positive or negative entropy change, S.

N2(g) + 3H2(g)  2NH3 (g)

Give answer as either positive or negative.

EASY
Diploma
IMPORTANT

Predict whether the following reactions will have a positive or negative entropy change, S.

N2O4(g)  2NO2 (g)

Give answer as either positive or negative.

EASY
Diploma
IMPORTANT

Predict whether the following reactions will have a positive or negative entropy change, S.

CaCO3 (s)  CaO(s) + CO2(g)

Give answer as either positive or negative.

EASY
Diploma
IMPORTANT

Predict whether the following reactions will have a positive or negative entropy change, S.

2C2H6 (g) +7O2 (g)  4CO2 (g) + 6H2O(l)

Give answer as either positive or negative.

EASY
Diploma
IMPORTANT

The equation for the reaction between carbon dioxide and hydrogen is shown below.

CO2 (g) + 4H2 (g)  CH4(g) + 2H2O(g)

The table shows the standard entropy values of the substances in the reaction above.

Substance CO2(g) H2(g) CH4(g) H2O(g)
S/JK-1 mol-1 214 131 186 189

Calculate the standard entropy change for the reaction. Explain how the sign can be predicted from the equation for the reaction.

EASY
Diploma
IMPORTANT

Calculate the Gibbs free energy change for the following reaction in kJ mol-1. Values for Gf are listed in the table.SO3(g) + H2O(l) H2SO4 (l)

Substance SO3(g) H2O(l) H2SO4(l)
Gf/kJ mol-1 -371.1 -228.6 -690.0

(Write the value correctly upto one decimal place)
 

 

 

EASY
Diploma
IMPORTANT

Calculate the Gibbs free energy change for the following reaction in kJ mol-1. Values for Gf are listed in the table.2NH4Cl(s) + CaO(s)  CaCl2 (s) + H2O(l) + 2NH3 (g)

Substance NH4Cl(s) CaO(s) CaCl2(s) H2O(l) NH3(g)
Gf/kJ mol-1 -202.9 -604.0 -748.1 -228.6 -16.5

(Write the value correctly up to one decimal place)

EASY
Diploma
IMPORTANT

Calculate the Gibbs free energy change for the following reaction in kJ mol-1. Values for Gf are listed in the table.C2H4(g) + H2O(l) C2H5OH(l)

Substance C2H4(g) H2O(l) C2H5OH(l)
Gf/kJ mol-1 +68.43 -228.6 -175

(Write the value correctly upto two decimal places)