Enthalpy Change and Types of Thermochemical Reactions

IMPORTANT

Enthalpy Change and Types of Thermochemical Reactions: Overview

This topic covers concepts, such as, Enthalpy of Reaction, Standard Enthalpy of Reactions, Exothermic Reactions & Endothermic Reaction etc.

Important Questions on Enthalpy Change and Types of Thermochemical Reactions

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Enthalpy change for the reaction,

  4H( g ) 2 H 2 ( g )is869.6kJ.

The dissociation energy of   HH bond is:

                               

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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.

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

                               

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

                               

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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:  

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

                               

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For the reaction:

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

at constant temperature, ΔHΔE is:

                               

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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

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If ΔHfoC2H6g=-85 kJ mol-1ΔHfoC3H8g=-104 kJ mol-1, ΔH°  for CsCg is 718 kJ mol-1 and heat of formation of H-atom is  218 kJ mol-1, then:

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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

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

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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

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You want to split carbon dioxide (CO2) into carbon and oxygen. If energy from coal were applied to drive the decomposition reaction, less CO2 would be released than consumed, because no process is perfectly efficient.

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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

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Write a thermochemical equation to depict standard enthalpy of sublimation ?

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

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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

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Given that C+O2CO2 , H° = - x kJ

2CO + O2 2CO2 , H°= - y kJ

The enthalpy of formation of carbon monoxide will be

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Which of the following reaction defines Hf°?

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