Chemistry - Energetics
Exam Duration: 45 Mins Total Questions : 30
Which one of the following statements is wrong?
- (a)
The brach of chemistry which deals with energy changes involved in chemical reactions, is called chemical energetics.
- (b)
Renewable source of energy is also called non-convetional source of energy.
- (c)
Non-renewal source of energy is also called non-convetional source of energy.
- (d)
Coal, lignite, natural gas, crude petroleum oil, uranium etc. are renewable sources of energy.
Given the reaction at 975\(?\) and 1 atm \(Ca{ CO }_{ 3 }\rightleftharpoons Cao(s)+{ CO }_{ 2 }(g);\Delta H=176kJ\) then \(\Delta\)E is equal to
- (a)
162 kJ
- (b)
165.6 kJ
- (c)
180 kJ
- (d)
186.4 kJ
Enthalpy of an element in its standard state at 25\(?\) and 1 atm pressure is always
- (a)
zero
- (b)
positive
- (c)
negative
- (d)
maximum
The heat of combustion of ethane, ethylene and hydrogen are 370.44 kcal, and 68.4 kcal respectively. The heat evolved in the formation of ethane \({ C }_{ 2 }{ H }_{ 4 }+{ H }_{ 2 }\rightarrow { C }_{ 2 }{ H }_{ 6 }\) would be
- (a)
- 31.30 kcal
- (b)
+ 31.30 kcal
- (c)
- 62.60 kcal
- (d)
+ 62.60 kcal
Given that \(\Delta\)H of the formation of CO2 (g) is - 393.13 kJ mole-1 and \(\Delta\)H of the formation of CO(g) is - 110.39 kJ mole-1. The \(\Delta\)H for the raction : \(CO(g)+1/2{ O }_{ 2 }\rightarrow { CO }_{ 2 }(g)\) would be
- (a)
- 282.74 kJ
- (b)
- 393.13 kJ
- (c)
- 503.63 kJ
- (d)
+ 282.74 kJ
The standard heat of formation of water and heats of combustion of acetylene and ethylene are - 68.3 kcal, - 310.6 kcal and - 337.2 kcal respectively. The heat of reaction for the hydrogenation of acetylene at constant volume and (25oC) would be
- (a)
- 44.40 kcal
- (b)
+ 41.10 kcal
- (c)
- 41.7 kcal
- (d)
+ 41.7 kcal
The bond dissociation energies of gases H2, Cl2 and HCl are 104, 58 and 103 kcal per mole respectively. The enthalpy of formation of HCl gas would be
- (a)
+ 44 kcal
- (b)
- 44 kcal
- (c)
+ 22 kcal
- (d)
- 22 kcal
Given the following data : C + O2 \(\rightarrow\) CO, \(\Delta\)H = - 94 kcal CO + 1/2 O2 \(\rightarrow\) CO2; \(\Delta\)H = - 67.7 kcal The heat of formation CO calculated from the data would be
- (a)
+ 40.4 kcal
- (b)
+ 26.3 kcal
- (c)
- 26.3 kcal
- (d)
52.6 kcal
Which one of the following statements is false?
- (a)
Work is a state function
- (b)
Temperature is a state function
- (c)
Change in the state is completely defined when the initial and final states are specified.
- (d)
Work appears at the boundary of the system
In thermodynamics a process is called reversible when
- (a)
surroundings and system change into each other
- (b)
there is no boundary between system and surroundings
- (c)
the surroundings are always in equilibrium with the system
- (d)
the system changes into the surroundings spontaneously
The heat of neutralisation of HCl and NaOH under certain condition is - 55.9 kJ and that of HCN by KOH is - 12.1 kJ. The heat of ionisation of HCN is
- (a)
- 68 kJ mol-1
- (b)
- 43.8 kJ mol-1
- (c)
68.8 kJ mol-1
- (d)
43.8 kJ mol-1
The Hess's law is an application of
- (a)
first law of thermodynamics
- (b)
second law of thermodynamics
- (c)
entropy change
- (d)
free change
Spontaneity of a chemical reaction is decided by the negative change in
- (a)
internal energy
- (b)
entropy
- (c)
enthalpy
- (d)
free energy
Who had proposed the following equation: \(\Delta\)G = \(\Delta\)H - T\(\Delta\)S
- (a)
Boltzmann
- (b)
Faraday
- (c)
Gibbs Helmholtz
- (d)
Thomson
For the process : dry ice \(\rightarrow\) CO2(g)
- (a)
\(\Delta\)H is -ve while \(\Delta\)\(\rho \) +ve.
- (b)
both \(\Delta\)H and \(\Delta\)\(\rho \) are +ve.
- (c)
both \(\Delta\)H and \(\Delta\)\(\rho \) are -ve.
- (d)
\(\Delta\)H is +ve while \(\Delta\)\(\rho \) is negative.
The entropy change involved in the isothermal reversible expansion of 5 moles of an ideal gas from a volume of 10 litres to 100 litres at 300 K would be
- (a)
26.88 cal degree-1
- (b)
27.88 cal degree-1
- (c)
22.88 cal degree-1
- (d)
36.88 cal degree-1
Evaporation of water is
- (a)
an exothermic change
- (b)
an endothermic change
- (c)
a process where no heat changes occur
- (d)
a process accompained by chemical reaction
Heat of neutralisation of strong acid against strong base is constant and is equal to
- (a)
- 13.7 kcal
- (b)
- 57 kJ
- (c)
- 5.7 \(\times\) 104 J
- (d)
ALL THE ABOVE
The difference between the heats of reaction at constant pressure and constant volume for the reaction \(2{ C }_{ 6 }{ H }_{ 6 }(l)+15{ O }_{ 2 }(g)\rightarrow 12{ CO }_{ 2 }(g)+6{ H }_{ 2 }O(l)\) at 25\(^oC\) in kJ is
- (a)
- 7.43
- (b)
+ 3.72
- (c)
- 3.72
- (d)
+ 7.43
Which of the following equations represents standard heat of formation of methene?
- (a)
C (diamond) + 2H2 (g) \(\rightarrow\) CH4(g)
- (b)
C (graphite) + 2H2 (g) \(\rightarrow\) CH4(g)
- (c)
C (diamond) + 4H (g) \(\rightarrow\) CH4(g)
- (d)
C (graphite) + 4H (g) \(\rightarrow\) CH4(g)
Variation of heat of reaction with temperature is known as
- (a)
Vant Hoff's isotherm
- (b)
Vant Hoff's isochore
- (c)
Kirchoff's equation
- (d)
none
In melting of ice
- (a)
enthalpy increses
- (b)
enthalpy decreses
- (c)
no change in enthalpy
- (d)
internal energy decreases
The formation of water from H2(g) and O2(g) is an exothermic reaction because
- (a)
H2(g) and O2(g) have a higher temperature than water
- (b)
H2(g) and O2(g) have higher chemical energy than water
- (c)
H2(g) and O2(g) have a lower chemical energy than water.
- (d)
NONE OF THESE
"When a system A is an thermal equilibrium with B and B is in thermal equilibrium with C, then A and C are in equilibrium with each other". This is a statement of
- (a)
zeroth law of thermodynamics
- (b)
first law of thermodynamics
- (c)
second law of thermodynamics
- (d)
third law of thermodynamics
Which one of the following statements is not correct?
- (a)
\(\Delta\)H is less than \(\Delta\)E for combustion of carbon to CO2
- (b)
In an exothermic reaction, the enthalpy of product is less than that of the reactants
- (c)
\( \Delta { H }_{ fus }=\Delta { H }_{ sub }-\Delta { H }_{ vap }\)
- (d)
A reaction for which \(\Delta\)H0 < 0 and \(\Delta\)S > 0 is possible at all temperatures.
For the transition C (diamond) \(\rightarrow\) C (graphite); \(\Delta\)H = - 1.5 kJ it follows that
- (a)
graphite is endothermic
- (b)
diamond is exothermic
- (c)
diamond is stable then graphite
- (d)
graphite is stabler than diamond
Which of the following expressions defines the physical significance of free energy change?
- (a)
\(\Delta\)G = W (expansion)
- (b)
-\(\Delta\)G = W (non-expansion)
- (c)
-\(\Delta\)G = - W (non-expansion)
- (d)
\(\Delta\)G = - W (expansion)
The sign of \(\Delta\)G for the process of melting of ice at 273 K and 1 atm pressure is
- (a)
+ ve
- (b)
- ve
- (c)
neither +ve nor -ve
- (d)
either +ve or -ve
For the process Dry ice \(\rightarrow\) CO2 (g)
- (a)
both \(\Delta\)H and \(\Delta\)S are -ve
- (b)
both \(\Delta\)H and \(\Delta\)S are +ve
- (c)
\(\Delta\)H is -ve while \(\Delta\)S is +ve
- (d)
\(\Delta\)H is +ve while \(\Delta\)S is -ve
A heat engine absoubs heat Q1 at temperature T1, and heat Q2 at temperature T2. Work done by the enge is (Q1 + Q2) J. This data
- (a)
violates 1st law of the thermodynamics
- (b)
violates 1st law of the thermodynamics if Q1 is -ve
- (c)
violates 1st law of the thermodynamics if Q2 is +ve
- (d)
does not violates 1st law of the thermodynamics.