Enthalpy Change of a Reaction

IMPORTANT

Enthalpy Change of a Reaction: Overview

This topic covers concepts, such as, Enthalpy Change, Enthalpy of Reaction, Exothermic Reactions and Endothermic Reaction etc.

Important Questions on Enthalpy Change of a Reaction

EASY
IMPORTANT

The enthalpy of hydrogenation of cyclohexene is   119.5kJmo l 1 .  If resonance energy of benzene is   150.4kJmo l 1 , its enthalpy of hydrogenation of benzene would be

                               

EASY
IMPORTANT

For which one of the following equations is ΔHreaction° equal to ΔHf° for the product?

                               

MEDIUM
IMPORTANT

What is the enthalpy change for,

2H2O2(l)2H2O(l)+O2(g) if heat of formation of  H2O2(l)  and  H2O(l)  are -188 and -286 kJ/molrespectively (in standard conditions)?

EASY
IMPORTANT

Assume each reaction is carried out in an open container. For which reaction will ΔH=ΔE ?

                               

EASY
IMPORTANT

For the reaction:

C3H8(g)+5O2(g)3CO2(g)+4H2O(l)

at constant temperature, ΔHΔE is:

                               

EASY
IMPORTANT

For the reaction

N2+3H2 2NH3,  ΔH=?

MEDIUM
IMPORTANT

The number of endothermic process/es from the following is _______.

A. I2( g)2I(g)

B. HCl(g)H(g)+Cl(g)

C. H2O(l)H2O(g)

D. C(s)+O2( g)CO2( g)

E. Dissolution of ammonium chloride in water

MEDIUM
IMPORTANT

For complete combustion of ethene,
C2H4( g)+3O2( g)2CO2( g)+2H2O(l)
the amount of heat produced as measured in bomb calorimeter is 1406 kJ mol-1 at 300 K. The minimum value of TΔS needed to reach equilibrium is (-) kJ. (Nearest integer)
Given: R=8.3 J K-1 mol-1

EASY
IMPORTANT

Given below are two statements related to Ellingham diagram :

Statement I : Ellingham diagrams can be constructed for formation of oxides, sulphides and halides of metals.

Statement II : It consists of plots of ΔH° vs T for formation of oxides of elements.

In the light of the above statements, choose the most appropriate answer from the options given below :

MEDIUM
IMPORTANT

The enthalpy change for the adsorption process and micelle formation respectively are

MEDIUM
IMPORTANT

C(s)+O2(g)CO2(g),ΔH=+94.0Kcal.


CO(g)+12O2(g)CO2(g),ΔH=67.7Kcal.


From the above reactions find how much heat (Kcal mole1) would be produced in the following reaction:


CO(g)+12O2(g)CO (g)

MEDIUM
IMPORTANT

H for the reaction,

Ag+BgABg at 298 K and 1 atm is -10 kcal.

The U for the above conversion would be

EASY
IMPORTANT

The heat change at constant volume for the decomposition of silver oxide is found to be 80.25 kJ . The heat change at constant pressure will be______. 

MEDIUM
IMPORTANT

The value for U for the reversible isothermal evaporation of 90 g water at 100 °C will be : (Hvap of water=40.8kJ mol1, R=8.314 JK1mol-1)

MEDIUM
IMPORTANT

The heat of combustion of ethylene at 18°C and at constant volume is  -335.8 kcal when water is obtained in liquid state. What is the heat of combustion at constant pressure and at 18°C ?

EASY
IMPORTANT

Calculate ΔH (in joules) for C(graphite)C(diamond) from the following data,

C(graphite+O2(g)CO2(g); ΔH=-393.5 kJ

C(diamond+O2( g)CO2(g); ΔH=-395.4 kJ

HARD
IMPORTANT

Nitroglycerine MW=227.1 detonates according to the following equations,

2C3H5NO33l3 N2g+12O2g+6CO2g+5H2Og

The standard molar enthalpies of formation, ΔHf° for all the compounds are given below.

ΔHf°C3H5NO33=-364 kJ/mol
ΔHf°CO2g=-393.5 kJ/mol
ΔHf°H2Og=-241.8 kJ/mol
ΔHf°N2g=0 kJ/mol
ΔHf°O2g=0 kJ/mol

The enthalpy change when 10 g of nitroglycerine is detonated is

MEDIUM
IMPORTANT

Which of the following is endothermic reaction :-

EASY
IMPORTANT

The difference between heat of reaction at constant pressure H and at constant volume (ΔE) for the reaction: Cs+12O2gCOg at a temperature =T K is 

(Assume R=0.002 kcal K-1mol-1)

HARD
IMPORTANT

Define enthalpy of chemical reactions. What is meant by standard state of a substance and standard enthalpy of reactions?