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AM CHEMISTRY > UNIT#08 THERMOCHEMSITRY AND ENERGETICS OF CHEMICAL REACTIONS > Flashcards

UNIT#08 THERMOCHEMSITRY AND ENERGETICS OF CHEMICAL REACTIONS Flashcards

1
Q

Thermodynamics does NOT deal with:

A

➡Heat of Reaction❌
➡Rate of Reaction✅
➡Spontaneity of Reaction❌
➡Entropy of Reaction❌

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2
Q

If an endothermic reaction is allowed to take place very rapidly in air, the temperature of the surrounding air will:

A

Decrease

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3
Q

The exothermic process is;

A

Respiration

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4
Q

A process, which takes place on its own without any outside assistance, is termed as:

A

Spontaneous

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5
Q

The work done by expansion of gas against constant pressure is:

A

-PΔV
(Work done by the system is considered negative)

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6
Q

A state function which describes together the internal energy and product of pressure and volume is called:

A

Enthalpy

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7
Q

The enthalpy of formation of a compound is:

A

Either positive or negative

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8
Q

Enthalpy is an expression for the:

A

Heat Energy

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9
Q

Which one of the following has a standard enthalpy of formation that is zero?

A

Cu (s)
➡Standard Enthalpy of an element in its standard state is zero

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10
Q

Which of the following statement is correct:

A

➡ΔH is positive for exothermic reaction❌
➡ΔH is negative for endothermic reaction❌
➡The heat of neutralization of strong acid with a strong base is always the same✅
➡The enthalpy of fusion is negative❌

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11
Q

What is not correct about ΔHf :

A

➡Its value gives an idea about the relative stability of reactants and the products❌
➡It is always negative❌
➡Value depends upon the nature of bonds✅
➡ITs value may be negative or positive❌

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12
Q

Which of the following has a positive value of enthalpy:

A

Atomization

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13
Q

NaOH + HCl ➡ NaCl + H2O
Enthalpy change in the above reaction is called:

A

Enthalpy of neutralization

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14
Q

Enthalpy o neutralization per mole of H2SO4/Ba(OH)2 is:

A

-54.7 kJmol-1

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15
Q

Which of the following processes has always ΔH= -ve

A

Combustion

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16
Q

Heat absorbed or evolved during the chemical reaction at constant pressure is:

A

ΔH

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17
Q

The change in enthalpy of a system when one mole of the substance is completely burnt in air or oxygen is called:

A

Heat of combustion

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18
Q

Which of the following enthalpy change may be positive or negative value:

A

➡ΔHc
➡ΔHsolution

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19
Q

Neutralization of acid-base is:

A

➡Spontaneous
➡Exothermic

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20
Q

ΔH represent the enthalpy change at;

A

25°C and 1 atm pressure

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21
Q

The enthalpy changes ΔH of a process are given by the relation:

A

ΔE = ΔH + PΔV

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22
Q

A system absorbs 100kJ heat and performs 50kJ work on the surroundings. The change in internal energy of the system is:

A

50kJ

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23
Q

Which equation represents the atomization of iodine:

A

1/2 I2(s) ➡ I(l)

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24
Q

The ΔH of a reaction is recorded at:

A

298K

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25
Q

Which of the following enthalpies is always negative;

A

Enthalpy of neutralization

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26
Q

Which of the following enthalpies is always positive:

A

Enthalpy of sublimation

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27
Q

Enthalpy of reaction can be measured in;

A

Glass calorimeter

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28
Q

How much heat is evolved by 100g of water when its temperature decreases from 25°C to 5°C?

A

-84,00J
(q = msΔT)
➡Specific Heat o water is 4.2 J/gK

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29
Q

Enthalpy of combustion of food, fuel and other compounds can be measured accurately by

A

Bomb Calorimeter

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30
Q

Which enthalpy of reaction can not be determined by glass calorimeter

A

Enthalpy of combustion

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31
Q

Total Heat energy (q) can be calculated in a bomb calorimeter by using the following:

A

c x ΔT
(q = c x ΔT)

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32
Q

Which one of the following is applied to calculate lattice energy indirectly?

A

Born-Haber cycle

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33
Q

In order to determine ΔHlattice of ionic compound which is the correct relationship?

A

ΔHlattice = ΔHf - ΔHx

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34
Q

Which equation shows lattice energy o ionic compound?

A

When one mole of an ionic compound is formed from its gaseous ions

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35
Q

With the increase in charge to size ratio of ions, the lattice energy:

A

Increases
(ΔHlattice ∝ Charge/Size of an atom)

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36
Q

Hess’s law is analogous to;

A

1st Law of Thermodynamics

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37
Q

Which of the following enthalpies of formation cannot be measured directly?

A

➡ΔH lattice for the ionic compound
➡ΔH for CO
➡ΔH for B2O3

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38
Q

The standard enthalpy changes of formation of carbon dioxide and water are -394kJmol-1 and -286kJmol-1 respectively, if the standard enthalpy change of combustion of propyne, C3H4 is -1932kJmol-1. What is the standard enthalpy change of formation?

A

-184 kJmol-1

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39
Q

The heat of combustion o ethane (C2H6) is -337.0 kcal at 25°C. The heat reaction when 3g of ethane is burnt completely is:

A

-33.7 kcal

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40
Q

Hess’s law is known as:

A

Law of heat summation

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41
Q

Relation between qp and qv:

A

qp > qv

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42
Q

The formation of SO3 from SO2 is ___ reaction.

A

Endothermic

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43
Q

For strong acid and strong base neutralization energy:

A

Constant

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44
Q

Unit of energy:

A

➡Joule
➡Kilojoule
➡Calorie

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45
Q

The unavailability of methods to find out the heat of reactions accurately makes thermochemistry

A

A limited field of study

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46
Q

Which one of the following is not an example of a state function?

A

Heat (q)

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47
Q

Temperature and volume in an experiment are part of :

A

State of a system

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48
Q

In endothermic reaction heat is absorbed from:

A

Surrounding

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49
Q

ΔH for the exothermic reaction is:

A

Negative

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50
Q

Which of the following condition is constant in the bomb calorimeter;

A

Volume

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51
Q

Heat exchanged between the system and surrounding at constant volume is shown by the relation

A

ΔH = qv + w

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52
Q

At constant volume, the heat supplied is equal to:

A

Internal energy change

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53
Q

Work done on the system is:

A

Positive

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54
Q

Which one is not a state function:

A

Work

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55
Q

Heat supplied at constant pressure equals:

A

Enthalpy

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56
Q

Enthalpy is the sum of the internal energy and:

A

Work done

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57
Q

Heat o a solution for the substance whose solubility decreases with an increase in temperature is:

A

Negative

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58
Q

Enthalpy change of solution of Na2Co2 is a ____ reaction

A

Exothermic reaction

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59
Q

An enthalpy cycle used to calculate the lattice energy is;

A

Born Haber cycle

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60
Q

Energy for the endothermic reaction is given a ___ value:

A

Positive

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61
Q

Which is correct for 1st law of thermodynamics?

A

ΔE = q +W

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62
Q

The energy of products is greater in:

A

Endo

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63
Q

Amount of heat absorbed by 2kg of water when temperature changes by 10°C are:

A

8400
(q = msΔT)

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64
Q

When a bond is formed, energy is;

A

Released

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65
Q

Which one is the state function?

A

PTVUHSG

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66
Q

What is the value of one calorie in Joule?

A

4.18J

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67
Q

The formation of carbon dioxide hinders calculating the heat of formation of;

A

CO

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68
Q

Decomposition of water into hydrogen and oxygen is a:

A

Endothermic Reaction

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69
Q

The heat of the formation of CO

A

-110 kJ/mol

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70
Q

When 40J heat is provided and 20J work is done, if the initial energy is 10J then the final internal energy is;

A

30J

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71
Q

In glass calorimeter, which is constant

A

Pressure

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72
Q

A spontaneous process is;

A

➡Unidirectional and Irreversible
➡Unidirectional and Real
➡Irreversible and Real

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73
Q

ΔH will be given a negative sign in:

A

Exothermic Reaction

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74
Q

Reactants have high energy than products;

A

Exothermic Reaction

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75
Q

The reaction of water with quick lime results in a rise in the temperature of the system. Using the concentration change, indicate the nature of reaction.

A

Exothermic Reaction

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76
Q

Which of the following enthalpy change is always exothermic?

A

Enthalpy of Combustion

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77
Q

The heat of formation of MgO is given below.
Mg + 1/2 O2 ➡MgO ΔH=-692 kJ/mol. This equation shows that:

A

The product is very stable

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78
Q

When one mole of gaseous hydrogen ions are dissolved in water to form an infinitely dilute solution, the amount of heat liberated is;

A

-1075 kJ/mol

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79
Q

In standard enthalpy of atomization heat of surrounding:

A

Decreases

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80
Q

The heat of formation (ΔH) for CO2 is;

A

-394 kJ/mol

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81
Q

2H2 + O2 ➡2H2O ΔH=205.5 kJ/mol
What will be the enthalpy change in the above reaction:

A

-205.5 kJ/mol

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82
Q

1/2 H2(g) ➡ H(g) ΔH=218 kJ/mol
In this reaction ΔH will be called:

A

Enthalpy of atomization

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83
Q

Determine the value of enthalpy of formation of NH4Cl:

A

-692 kJmol-1

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84
Q

Enthalpy is measured at:

A

298K and 1 atm

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85
Q

When two moles of H2 and one mole of O2 react to form H2O 484 KJ heat is evolved what is ΔHf for one mole of H2O

A

-242 KJmol-1

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86
Q

The lattice energy of an ionic crystal is the enthalpy of

A

Formation

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87
Q

The thermal energy at constant pressure is called:

A

Enthalpy

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88
Q

The born-Haber cycle is used to determine the lattice energies of;

A

Ionic Solids

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89
Q

One calorie is equal to;

A

4.18J

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90
Q

The net change in energy in a chemical reaction is the same whether it takes place directly or indirectly. It is called:

A

Hess’s Law

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91
Q

The enthalpy of formation of an ionic compound is -392kJ/mol. Total energy changes (ΔHx) involved in the formation of gaseous ions from normal physical state is 280kJ/mol. The enthalpy of lattice is:

A

-672 kJ/mol

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92
Q

Enthalpy of neutralization of strong acids and bases is same because:

A

H+ and OH- combine to form H2O

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93
Q

Unit of heat is SI system is:

A

J

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94
Q

If there is interconversion of sloid and liquid states then:

A

➡ΔV = 0
➡ΔH = ΔE

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95
Q

First law of thermodynamics relates:

A

➡Internal Energy
➡Heat
➡Work

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96
Q

An exothermic process is:

A

O (g) + 1e- ➡O-1

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97
Q

If an endothermic reaction is allowed to take place very rapidly in air the temperature of the surrounding air:

A

Decreases

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98
Q

Which of the following sets constitutes of all the state functions of system:

A

➡Enthalpy
➡Entropy
➡Internal Energy

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99
Q

___ is not a state function.

A

Heat

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100
Q

Which of the following enthalpy change (ΔH) is always endothermic

A

ΔH (atomization)

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101
Q

Incorrect statement about endothermic reaction is;

A

➡Evaporation is an endothermic process❌
➡Products are more stable than reactants✅
➡ΔH is positive❌
➡Reaction mixture becomes stable❌

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102
Q

Among the followign changes, which is exothermic?

A

➡Freezing
➡Condensation
➡Combustion

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103
Q

Which of the followign process will be spontaneous and endothermic:

A

➡Melting of ice
➡Evaporation of water
➡Dissolution of NH4Cl

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104
Q

When water is added to quicklime, the reaction is:

A

Explosive

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105
Q

Which is non-spontaneous reaction?

A

N2 + O2 ➡2NO

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106
Q

The sum of all the energies of atoms, molecules or ions within a system is called:

A

Internal Energy

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107
Q

Which statement is true when liquid is converted into vapors?

A

Heat is absorbed

108
Q

When ΔE of a system increases, then which of the following possibilities is correct?

A

➡Temperature of the system can increase
➡Phase change may take place
➡Chemical reaction can occur

109
Q

ΔH = ΔE for which of the following reaction

A

K + H2O ➡ KOH + H2

110
Q

According to first law of thermodynamics energy rom system to surrounding can be transferred in the form of:

A

Heat and Work

111
Q

Change in enthalpy of ΔH of a gaseous system can be calculated by following relationship:

A

ΔH = ΔE + PΔV

112
Q

The amount of heat evolved when one mole of CH3COOh reacts with one mole of NaOH is:

A

< 57.4 kJ

113
Q

Standard enthalpies of formation of O3, CO2, NH3 and HI are 142.2, -33.3, -46.2 and +25.9 kJ/mol respectively. The order o their increasing stabilities will be:

A

O3, HI, NH3, CO2

114
Q

The enthalpy change for the reaction C(s) + O2(g) ➡ CO2 is called:

A

➡Enthalpy of formation
➡Enthalpy of combustions
➡Enthalpy of reaction

115
Q

Which of the following processes has always ΔH = -ve

A

Combustion

116
Q

Which one of the followin g reactions represent both standard enthalpy of combustion as well as standard enthalpy of formation

A

C (s) + O2 ➡ CO2(g)

117
Q

The enthalpy of atomization of H2 is 218kJ/mole, the enthalpy of formation of H2 from gaseous atoms:

A

-218 kJ/mole

118
Q

Which reaction shows enthalpy of formation:

A

C + O2 ➡CO2

119
Q

The enthalpy of formation of an ionic compound is -392 kJ/mol. Total energy changes involved in the formation of gaseous ions form normal physical state is 280 kJ/mol. The enthalpy of lattice is:

A

-672 kJ/mol

120
Q

Which of the following change in enthalpy in Born-Haber cycle may be negative

A

H (E.A)

121
Q

Hess Law follows:

A

➡First law of thermodynamics
➡Law of conservation of energy

122
Q

The net heat change i a chemical reaction is same whether it is brought about in two or more different ways in one or several steps. It is known as:

A

Hess’s Law

123
Q

Standard heat of formation of Al2O3 cannot be determined directly because:

A

Protective layer of Al2O3 form

124
Q

One joule is equivalent to:

A

1/4.184 Cal

125
Q

The enthalpies of all elements in their standard states are;

A

Zero

126
Q

____ is not a state function.

A

Heat

127
Q

No work is done at constant:

A

V

128
Q

For an endothermic reaction, enthalpy of reactants:

A

Is smaller than that of the products

129
Q

Most of the reactions which give stable products are;

A

Exothermic

130
Q

Decomposition of H2O is;

A

Endothermic reaction

131
Q

What type of reaction constitutes a limiting case between spontaneous and non-spontaneous reactions:

A

Reversible Reaction

132
Q

In an endothermic reaction:

A

Er < Ep

133
Q

In an exothermic reaction the heat energy is ______ while in an endothermic reaction it is;

A

➡Released
➡Absorbed

134
Q

Whenever a reaction is endothermic, then it means that:

A

Heat is transferred from the surroundings to the system

135
Q

Enthalpy of neutralization of strong acids and strong bases have the same values because;

A

The net change involves the combination of H+ and OH- ions to form water

136
Q

The measurement of enthalpy change at standard conditions means that we should manage the measurement at:

A

25°C at 1 atm

137
Q

The enthalpy change for the reaction C2H2 + 5/2 O2 ➡2CO2 + H2O is known as enthalpy of:

A

Enthalpy of Combustion

138
Q

BaCl2 + H2SO4 ➡ BaSO4 + HCl, an exothermic reaction, the heat change represented by the above equation is called;

A

Heat of Reaction

139
Q

The enthalpy of atomization of H2 is 218 kJ/mol and the enthalpy of formation of H2 from gaseous atoms

A

-436 kJ/mol

140
Q

An enthalpy change which is always exothermic:

A

ΔHn
(Enthalpy of Neutralization)

141
Q

The enthalpy change for the reaction, C2H5OH + 3O2 ➡ 2CO2 + 3H2O is known as enthalpy of;

A

Combustion of C2H5Oh

142
Q

Which of the following gases have the highest heat of combustion

A

Acetylene

143
Q

Which one of the following pairs has a maximum enthalpy of neutralization;

A

HCl + NaOH

144
Q

ΔH of a system can be calculated by which of the following relationship

A

q = m x s x ΔT

145
Q

Bomb calorimeter is used to determine the;

A

ΔHc

146
Q

What is the unit of molar heat capacity?

A

J/mol¹K¹

147
Q

This is true about the lattice energy of an ionic compound

A

➡Cannpt be determined directly
➡Can be obtained by means of the Born Haber cycle

148
Q

The enthalpy of formation of an ionic compound is -392 kJ/mol. Total energy changes (ΔHx) involved in the formation of gaseous ions from a normal physical state is 280 kJ/mol. The enthalpy of the lattice is;

A

-672 kJ/mol

149
Q

Choose from the following the correct statement about the Born Haber cycle

A

The lattice energy of crystalline substances can be calculated easily

150
Q

Standard heat of formation of Al2O3 cannot be determined directly because:

A

A protective layer of Al2O3

151
Q

The heat of combustion of graphite at 25°C is -393.51 kJ/ mol and that of a diamond is -395.41 kJ/mol. What is the enthalpy for the conversion of graphite into diamond at the same temperature?

A

+1.9 kJ/mol

152
Q

By applying Hess’s Law, we can calculate:

A

ΔH

153
Q

Enthalpy of neutralization of strong acids and strong bases have the same values because:

A

The net change involves the combination of H+ and OH- ions to form water.

154
Q

For an endothermic reaction, enthalpy of reactants

A

Is smaller than that of the products

155
Q

Which of the following has a positive value of enthalpy

A

Atomization

156
Q

The net heat change in a chemical reaction is the same whether it is brought about in two or more different ways in one or several steps. It is known as;

A

Hess’s Law

157
Q

Hess’s Law is analogous to;

A

Law of Heat summation

158
Q

NaOH + HCl ➡NaCl + H2O. Enthalpy change in the above reaction is called;

A

ΔH = ΔE

159
Q

A calorie is equivalent to:

A

4.184 J

160
Q

The values of ΔH for the process I + e ➡ I-1 are;

A

< O

161
Q

The enthalpy of formation of a compound is;

A

Either Positive or Negative

162
Q

What is correct about the heat of combustion:

A

It is always negative

163
Q

What is not correct about ΔHf:

A

It is always negative

164
Q

If an endothermic reaction is allowed to take place very rapidly in air, the temperature of the surrounding air will;

A

Decrease

165
Q

Q
One Joule is equivalent to:

A

1/4.184 cal

166
Q

The heat of reaction depends upon:

A

➡Temperature of the Reaction
➡Physical states of the reactants and the products

167
Q

The exothermic process is;

A

Respiration

168
Q

During an exothermic or endothermic reaction, one of the following formulas is used to calculate the amount of heat evolved or absorbed:

A

q = m x s x ΔT

169
Q

Most of the reactions which give stable products are;

A

Exothermic

170
Q

The measurement of enthalpy change at standard conditions means that we should manage the measurement at:

A

25°C at 1 atm

171
Q

The total heat content of a system is called:

A

Enthalpy

172
Q

The enthalpies of all elements in their standard states are;

A

Zero

173
Q

A state function which describes together the internal energy and product of pressure and volume is called

A

Enthalpy

174
Q

The enthalpy change for the reaction C2H2 + 5/2 O2 ➡ 2CO2 + H2O is known as enthalpy of;

A

Combustion of C2H2

175
Q

The value of ΔV is very small. The term PΔV can be neglected for processes involving:

A

➡Liquid
➡Solid

176
Q

The lattice energy of NaCl is;

A

-787 kJ/mol

177
Q

Decomposition of H2O is :

A

Endothermic Reaction

178
Q

According to Hess’s Law, the enthalpy change for a reaction:

A

independent of the path

179
Q

Enthalpy of formation of one mole of ionic compound form gaseous ion under standard condition is called;

A

Lattice Energy

180
Q

Change in enthalpy (ΔH) of a system can be calculated as;

A

ΔH = ΔE + PΔV

181
Q

If the internal energy of the system is increased:

A

➡Change in the state of the system may occur
➡Temperature of the system may rise
➡Chemical reaction may take place

182
Q

Enthalpy of a reaction can be measured by:

A

Glass calorimeter

183
Q

In order to determine ΔH of ionic compound which is the correct relationship:

A

ΔH (Lattice) = ΔHf - ΔHx

184
Q

Enthalpy of neutralization per mole of H2SO4/ Ba(OH)2 is;

A

-57.4 kJ/mol

185
Q

Whenever a reaction is endothermic, then it means that ;

A

Heat is transferred from the surroundings to the system

186
Q

How much heat is absorbed by 100g of water when its temperature decreases from 25°C to 5°C
(Heat capacity is 4.2 k/gK)

A

-84,00 J

187
Q

One of the best applications of Hess’s law to calculate the lattice energy of ionic compound is;

A

Born-Haber Cycle

188
Q

ΔH of a system can be calculated by which of the following relationships:

A

q = m x s x ΔT

189
Q

Which of the following processes has always ΔH= -ve

A

Dissolution of an ionic compound

190
Q

ΔH = ΔE is true for which of the following reaction?

A

▶K + H2O ➡ KOH + H2❌
▶N2 + 3H2 ➡ 2NH3❌
▶AlCl3 + 3NaOH ➡ Al(OH)3 + 3NaCl✅
▶ 4Na + O2 ➡ 2Na2O❌

191
Q

BaCl + H2SO4 ➡ BaSO4 + HCl ΔH =-22.4 kJ/mol, the heat change represented by the above equation is called;

A

The heat of the reaction of BaSO4

192
Q

When water is added to quick lime, the reaction is:

A

Exothermic

193
Q

What type of reaction constitutes a limiting case between spontaneous and non-spontaneous reactions;

A

Reversible Reaction

194
Q

Thermodynamics does NOT deal with

A

Rate of Reaction

195
Q

____ is not a state function.

A

Heat

196
Q

The enthalpy of atomization of H2 is 218 kJ/mole and the enthalpy of formation of H2 from gaseous atoms:

A

-436 kJ/mol

197
Q

The enthalpy change for the reaction C + O2 ➡ CO2 is called:

A

➡Enthalpy of formation
➡Enthalpy of reaction
➡Enthalpy of combustion

198
Q

Which equation shows lattice energy for the ionic compound?

A

Na+ + Cl- ➡NaCl

199
Q

A process which is spontaneous and endothermic;

A

H2O(l) ➡ H2O(g)

200
Q

An enthalpy change which is always exothermic

A

ΔHn

201
Q

All of the following are exothermic processes except:

A

Evaporation

202
Q

Enthalpy of combustion of food, fuel and other compounds can be measured accurately by:

A

Bomb Calorimeter

203
Q

The enthalpy of formation of an ionic compound is -392 kJ/mol. Total energy changes (ΔH) involved in the formation of gaseous ions from the normal physical state is 280 kJ/mol. The enthalpy of the lattice is;

A

-672 kJ/mol

204
Q

Which of the following enthalpies of formation cannot be measured directly:

A

➡ΔH(lattice) of an ionic compound
➡ΔHf for CO
➡ΔHf for B2O3

205
Q

All are slow processes except:

A

The reaction of AgNO3 with NaCl

206
Q

Heat absorbed or evolved during the chemical reaction at constant pressure is;

A

ΔH

207
Q

A bomb calorimeter is used to determine the:

A

ΔHc

208
Q

Which enthalpy of reaction can not be determined by glass calorimeter

A

Enthalpy of combustion

209
Q

Which is not related to state function:

A

➡It deals with atomic level✅
➡It is a macroscopic property❌
➡It depends upon initial and final values❌
➡It is independent on apth❌

210
Q

In an endothermic reaction:

A

Er < Ep

211
Q

Standard heat of formation of Al2O3 cannot be determined directly because:

A

Protective Layer of Al2O3

212
Q

In an exothermic reaction, the heat energy is ___ while in an endothermic reaction it is___

A

➡Released
➡Absorbed

213
Q

Which one is the endothermic and spontaneous process

A

Melting of Ice

214
Q

One kilo calorie is equal to;

A

4184 J

215
Q

By convention, the standard heat of formation of all elements is assumed to be:

A

Zero

216
Q

The change in enthalpy of a system when one mole of the substance is completely burnt in excess of air or oxygen is called:

A

Heat of combustion

217
Q

Which of the following enthalpy change always have a negative value:

A

ΔHc

218
Q

The change in enthalpy when one mole of a substance is dissolved in a specified quantity of solvent at a given temperature is called;

A

Heat of Solvation

219
Q

Neutralization of acid-base is;

A

➡Spontaneous
➡Non-Spontaneous

220
Q

The born-Haber cycle is an application of;

A

Hess’s law

221
Q

ΔH represent the enthalpy change at;

A

25°C and 1 atm pressure

222
Q

The enthalpy change ΔH of a process is given by the relation:

A

ΔH = ΔE + PΔV

223
Q

A system absorbs 100 kJ heat and performs 50kJ work on the surroundings. the increase in internal energy of the system is:

A

50K

224
Q

Which equation represents the atomization of iodine ;

A

1/2 I2 (s) ➡I (g)

225
Q

The heat of combustion of ethane is -337.0 kcal at 25°C. The heat of the reaction when 3g of ethane is burnt completely is;

A

-33.7 kcal

226
Q

The heat of combustion of graphite at 25°C is 393.51 kJ/mol ad that of a diamond is 395.41 kJ/mol. What is the enthalpy for the conversion of graphite into diamond at the same temperature?

A

+1.9 kJ/mol

227
Q

The standard enthalpy changes of the formation of carbon dioxide and water are -394kJ/mol and -286 kJ/mol respectively, if the standard enthalpy change of combustion of propyne, C3H4 is -1938 kJ/mol. What is its standard enthalpy change of formation?

A

-184 kJ/mol

228
Q

Total heat energy (q) can be calculated in a bomb calorimeter by using the following formula:

A

c x ΔT

229
Q

Enthalpy of neutralization of strong acids and strong bases have same values of because:

A

The net change involves the combination of H+ and OH- ions to form water

230
Q

For endothermic reaction, enthalpy of reactions:

A

Is smaller than that of the products

231
Q

Which of the following has positive value of enthalpy:

A

Atomization

232
Q

The net heat change in a chemical reaction is the same whether it is brought about in two or more different ways in one or several steps. It is known as:

A

Hess’s Law

233
Q

Hess’s law is analogus to:

A

Law of heat summation

234
Q

NaOH + HCl ➡NaCl + H2O.
Enthalpy change in the above reaction is called

A

Enthalpy of neutralization

235
Q

If a reaction involves only solids and liquids, which of the following is true?

A

ΔH = ΔE

236
Q

Calorie is equivalent to:

A

4.184 J

237
Q

The values of ΔH or the process I(g) + e- ➡I-1 is :

A

<0

238
Q

The enthalpy of formation of a compound is:

A

Either positive or negative

239
Q

What is correct about heat of combustion:

A

It is always negative

240
Q

What is not correct about ΔH:

A

➡ It is always negative✅
➡ Its value is gives an idea about the realtive stability of reactants and products❌
➡ Value depends upon nature of bonds❌
➡ Its value can be greater or less than zero❌

241
Q

If an endothermic reaction is allowed to take place very rapidly in air, the temperature of the surrounding air will:

A

Decrease

242
Q

One Joule is equivalent to:

A

1/4.184 cal

243
Q

The heat of reaction depends upon

A

➡Temperature of the reactants
➡Physical States of the reactants and the products

244
Q

The exothermic process is:

A

Respiration

245
Q

During an exothermic process or endothermic reaction one of the following formulas is used to calculate the amount of heat evolved or absorbed:

A

q = m x s x ΔT

246
Q

Most of the reactions which give stable products are

A

Exothermic

247
Q

The measurement of enthalpy change at standard conditions means that we should manage the measurement at;

A

25°C at 1 atm

248
Q

Total heat content of a system is called:

A

Enthalpy

249
Q

The enthalpies of all elements in their standard states are:

A

Zero

250
Q

A state function which describees together the internal energy and product of pressure and volume is called;

A

Enthalpy

251
Q

The enthalpy change for the reaction C2H2 + 5/2 O2 ➡2CO2 +H2O. is known as the enthalpy of:

A

COmbustion of C2H2

252
Q

The value of ΔV being very small. The term PΔV can be neglected for process involving:

A

➡Liquid
➡Solid

253
Q

The lattice energy of NaCl is:

A

-787 kJ/mole

254
Q

Decomposition of H2O is :

A

Endothermic reaction

255
Q

According to Hess’s law ,the enthalpy change for a reaction:

A

Independent of the path

256
Q

Enthalpyof formaton of one mole of ionic compound form gaseous ion under standard condition is called:

A

Bond Energy

257
Q

Choose from the followings the correct statements about Born Haber cycle:

A

The energy changes in a cyclic process is not zero

258
Q

Change in enthalpy (ΔH) of a system can be calculated by:

A

ΔH = ΔE + PΔV

259
Q

If internal energy of the system is increased:

A

➡Change in state of the system may occur
➡Temperature of the system may rise
➡Chemical reaction may take place

260
Q

Enthalpy of a reaction can be measured by:

A

Glass Calorimeter

261
Q

To determine ΔH of ionic compound which is the correct relationship

A

ΔH (lattice) = Hf - Hx

262
Q

Enthalpy of neutralization per mole of H2SO4/ Ba(OH)2 is:

A

-57.4 kJ/mole

263
Q

Whenever a reaction is endothermic , then it means that:

A

Heat is transferred from the surroundings to the system

264
Q

How much heat is abosrbed by 100g of water when ts temperature decreases from 25°C to 5°C?
(Heat capacity of H2O=4.2 J/gK)

A

-84,00J

265
Q

One of the best applications of Hess’s law to calculate the lattice energy of ionic compound is:

A

Born Haber Cycle

AM CHEMISTRY (19 decks)

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