Enthalpy Change of a Reaction- Reaction Enthalpy

IMPORTANT

Enthalpy Change of a Reaction- Reaction Enthalpy: Overview

This topic covers concepts such as Enthalpy of Reaction, Standard Enthalpy of Reactions, Enthalpy of Formation, Standard Enthalpy of Formation, Enthalpy Change during Phase Transformations, Enthalpy of Fusion, Enthalpy of Vaporization, etc.

Important Questions on Enthalpy Change of a Reaction- Reaction Enthalpy

EASY
IMPORTANT

Enthalpy change for the reaction,

  4H( g ) 2 H 2 ( g )is869.6kJ.

The dissociation energy of   HH bond is:

                               

MEDIUM
IMPORTANT

From the data of following bond energies:

 HHbondenergy:431.37kJmol1C=Cbondenergy:606.10kJmol1CCbondenergy:336.49kJmol1CHbondenergy:410.50kJmol1

Calculate the enthalpy of the following reaction in kJmol1.

Question Image 

 

                               

EASY
IMPORTANT

Given that bond energies of HH  and  ClCl  are  430 kJmol1and240kJmol1respectively and ΔHf for HClis −90 kJmol1, bond enthalpy of HCl is:

                               

EASY
IMPORTANT

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

                               

MEDIUM
IMPORTANT

Bond dissociation enthalpy of   H 2 , C l and HCl  are  434, 242  and  431  kJ  mo l 1 respectively. The enthalpy of formation of HCl is:  

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:

                               

MEDIUM
IMPORTANT

Standard heat of formation of SF6(g)S(g) and F(g) are: -1100, 275 and 80 kJ mol-1, respectively. Then, the average value of S-F bond energy in SF6 is

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

EASY
IMPORTANT

Enthalpy of vaporisation can be defined as the enthalpy change that accompanies the vaporisation of ten moles of liquid at any temperature and pressure.

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

EASY
IMPORTANT

From the following data
CH3OHl+32O2gCO2g+2H2Ol; ΔrH°=-726 kJ mol-1
H2g+12O2gH2Ol; ΔrH°=-286 kJ mol-1
Cgraphite+O2gCO2g; ΔrH°=-393 kJ mol-1
The standard enthalpy of formation of CH3OHl in kJ mol-1 is

HARD
IMPORTANT

Write a thermochemical equation to depict standard enthalpy of sublimation ?

HARD
IMPORTANT

Standard enthalpy of _____ is the change in enthalpy when one mole of a solid substance sublimes at a constant temperature and under standard pressure.

HARD
IMPORTANT

A container holds 2 moles of gas A and 3 moles of gas B in it at a constant pressure of 2 bar. The gases are separated by a wall and the whole container is held in an ice bath at a constant temperature of 0°C. The wall is removed and the gases mix and react to form C by the reaction given below. After the reaction comes to equilibrium how many grams of the ice have melted ? Consider that all heat produced in reaction has been utilized in melting of ice.

A g + B g C g

Compound Δ f H kJ mol -1 S M JK -1 mol -1
A 0 165
B - 90 200
C - 150 250


All data above is at 298 K. ΔFUSHwater, 0=6 kJ mol-1.

Read the passage and answer the following questions as single choice correct . Given 273 × 8.314 × 2.303 = 5227 J m -1

Mass of ice melted in the reaction may be

EASY
IMPORTANT

Given that C+O2CO2 , H° = - x kJ

2CO + O2 2CO2 , H°= - y kJ

The enthalpy of formation of carbon monoxide will be

EASY
IMPORTANT

Which of the following reaction defines Hf°?

EASY
IMPORTANT

In the reaction : S+3/2 O2SO3+2x kcal and SO2+1/2O2SO3+y kcal,
heat of formation of SO2 is

EASY
IMPORTANT

Given the following equations and H° values at 25°C,

 2H3BO3(aq)B2O3(s)+3H2O(l), H°=+14.4 kJ mol-1.

H3BO3(aq)HBO2(aq)+H2O(l), H°=-0.02 kJ mol-1.

H2B4O7(s)2B2O3(s)+H2O(l), H°=17.3 kJ mol-1.

Calculate H° for the following reaction, H2B4O7(s)+H2O(l)4HBO2(aq).

EASY
IMPORTANT

Given the following equations and H° values at 25 °C,

Si(s)+O2(g)SiO2(s),H°=-911 kJ mol-1.

2C(graphite) + O2 (g)  2CO(g),H°=-221 kJ mol-1.

Si (s)+C(graphite)SiC (s), H°=- 65.3 kJ mol-1.

Calculate H° for the following reaction, SiO(s)+3C(graphite)SiC(s)+2CO(g).