CBSE Questions for Class 11 Medical Chemistry Thermodynamics Quiz 3 - MCQExams.com

For the change, $$C_{diamond}\longrightarrow +C_{graphite}; \:\Delta H=-1.89 \:kJ$$, if 6 g of diamond and 6 g of graphite are separately burnt to yield $$CO_2$$ the heat liberated in first case is:
  • less than in the second case by 1.89 kJ
  • less than in the second case by 11.34 kJ
  • less than in the second case by 14.34 kJ
  • more than in the second case by 0.945 kJ
The relationship between the free energy change $$(\Delta G)$$ and entropy change $$(\Delta S)$$ at constant temperature $$(T)$$ is 
  • $$\,\Delta G = \Delta H + T\Delta S$$
  • $$\,\Delta H = \Delta G + T\Delta S$$
  • $$\,T\Delta S = \Delta G + \Delta H$$
  • $$\,\Delta G = -\Delta H - T\Delta S$$
Hess law is applicable for determination of enthalpy of
  • Reaction
  • Formation
  • Transition
  • All of above
A change in the free energy of a system at constant temperature and pressure will be:

$$\Delta_{ sys }G = \Delta_{ sys }H - T\Delta_{ sys }S$$

At constant temperature and pressure
$$\Delta_{ sys }G < 0 (spontaneous)$$
$$\Delta_{ sys }G = 0 (equilibrium)$$
$$\Delta_{ sys }G > 0 (non-spontaneous)$$

The free energy for a reaction having $$\Delta H = 31400  cal$$, $$\Delta S = 32  cal  K^{ -1 }  mol^{ -1 }$$ at $$1000^{ \circ }C$$ is?
  • $$-9336 cal$$
  • $$-7006 cal$$
  • $$-2936 cal$$
  • $$+9006 cal$$
The heat of hydrogenation of ethene is $$x_1$$ and that of benzene is $$x_2$$
Hence resonance energy of benzene is
  • $$x_1 - x_2$$
  • $$x_1 + x_2$$
  • $$3x_1 - x_2$$
  • $$x_1 - 3x_2$$
$$C(diamond) + 2H_2(g)\longrightarrow CH_4(g);\,\,\Delta H_1$$ 

$$C(g) + 4H(g)\longrightarrow CH_4(g);\,\,\Delta H_2$$

Select the correct relation.
  • $$\Delta H_1 = \Delta H_2$$
  • $$\Delta H_1 > \Delta H_2$$
  • $$\Delta H_1 < \Delta H_2$$
  • $$\Delta H_1 = \Delta H_2 + \Delta_{ vap }H(C) + \displaystyle \Delta_{ diss }H(H_2)$$
Which one of the following correctly represents the physical significance of Gibb's energy change?
  • $$\displaystyle -\Delta G={ W }_{ \text{compression} }$$
  • $$\displaystyle \Delta G={ W }_{ \text{expansion} }$$
  • $$\displaystyle \Delta G={ -W }_{ \text{expansion} }={ W }_{ \text{non-expansion} }$$
  • $$\displaystyle -\Delta G={ W }_{ \text{expansion} }$$
The Born Haber cycle below represents the energy changes occurring at 298K when KH is formed from its elements
v : $${ \Delta H }_{ atomisation }$$ K = 90 kJ/mol
w : $${ \Delta H }_{ ionisation }$$ K = 418 kJ/mol
x : $${ \Delta H }_{ dissociation }$$ H = 436 kJ/mol
y : $${ \Delta H }_{ electron affinity }$$ H = 78 kJ/mol
z : $${ \Delta H }_{ lattice }$$ KH = 710 kJ/mol
In terms of the letters v to z the expression for
$${ \Delta H }_{ i }$$ of K is $${ \Delta H }_{ i }$$ = $$w/2$$.
If true enter 1, else enter 0.
  • 0
  • 1
  • 2
  • 3
$$H_2(g) + Br_2(g)\longrightarrow 2HBr(g);  \Delta H^{ \ominus } = -72.40  kJ$$
$$\Delta G^{ \ominus } = -106.49  kJ, T = 298  K$$
The value $$\Delta S$$ is . 
  • $$114.3 J k^{ -1 }$$
  • $$-114.3 J k^{ -1 }$$
  • $$1363.6 J k^{ -1 }$$
  • Noe of these
Based on the first law of thermodynamics, which one of the following is correct ?
  • $$\text{For an isochoric process, E = -Q}$$
  • $$\text{For an adiabatic process, E = -Q}$$
  • $$\text{For an isothermal process, E = -Q}$$
  • $$\text{For an cyclic process, W = -Q}$$
A bomb calorimeter is used to measure the value of heat of reaction at a constant
  • Volume
  • Pressure
  • Temperature
  • None of these
All spontaneous process proceed in one direction only.
  • True
  • False
$$H_2(g) + \frac{ 1 }{ 2 }O_2(g)\longrightarrow 2H_2O(l);   \Delta H = -286  kJ$$
$$2H_2(g) + O_2(g)\longrightarrow 2H_2O(l)......... kJ(\pm?)$$
  • $$2H_2(g) + O_2(g)\longrightarrow 2H_2O(l) + 572 kJ$$.
  • $$2H_2(g) + O_2(g)\longrightarrow 2H_2O(l) - 572 kJ$$.
  • $$2H_2(g) + O_2(g)\longrightarrow 2H_2O(l) +0 kJ$$.
  • None of these
The Born Haber cycle below represents the energy changes occurring at 298K when KH is formed from its elements
v : $${ \Delta H }_{ atomisation }$$ K = 90 kJ/mol
w : $${ \Delta H }_{ ionisation }$$ K = 418 kJ/mol
x : $${ \Delta H }_{ dissociation }$$ H = 436 kJ/mol
y : $${ \Delta H }_{ electron affinity }$$ H = 78 kJ/mol
z : $${ \Delta H }_{ lattice }$$ KH = 710 kJ/mol
In terms of the letters v to z the expression for
$${ \Delta H }_{ electron affinity }$$ of H is $${ \Delta H }_{ electron affinity }$$  is __.
I
  • $$y$$
  • $$y/2$$
  • $$2y$$
  • $$y/3$$
The heat released when the requisite amount of ions in the gaseous state combine to give 1 mol of crystal lattice is known as:
  • lattice energy
  • hydration energy
  • formation energy
  • none of the above
The enthalpy change for reaction (i) is:
  • + 100.23 kJ/mol
  • + 127.5 kJ/mol
  • - 127.5 kJ/mol
  • - 100.23 kJ/mol
Gibbs- Helmholtz equation is
  • $$\Delta G = \Delta H - T\Delta S$$.
  • $$\Delta G = \Delta H +T\Delta S$$.
  • $$\Delta G = T\Delta H - \Delta S$$.
  • none of these
What can be concluded about the values of $$\Delta H$$ and $$\Delta S$$ from this graph ?

259039.jpg
  • $$\Delta H >0, \:\Delta S >0$$
  • $$\Delta H >0, \:\Delta S <0$$
  • $$\Delta H <0, \:\Delta S >0$$
  • $$\Delta H <0, \:\Delta S <0$$
State True or False.
Gibbs- Helmholtz equation is $$\Delta G = T\Delta H - \Delta S$$.
  • True
  • False
The Born Haber cycle below represents the energy changes occurring at 298K when $$KH$$ is formed from its elements
v : $${ \Delta H }_{ atomisation }$$ $$K = 90 kJ/mol$$
w : $${ \Delta H }_{ ionisation }$$ $$K = 418 kJ/mol$$
x : $${ \Delta H }_{ dissociation }$$ $$H = 436 kJ/mol$$
y : $${ \Delta H }_{ electron affinity }$$ $$H = 78 kJ/mol$$
z : $${ \Delta H }_{ lattice }$$ $$KH = 710 kJ/mol$$
Calculate the value of $$\Delta $$$$H$$ showing all your working.
  • 124 kJ/mol
  • -124 kJ/mol
  • 124 J/mol
  • None of these
$$2$$ moles of $$CO$$ and $$1$$ mole of $$O_{2}$$ are taken in a container of volume $$1$$ litre to form $$2$$ moles of $$CO_{2}$$ according to equation

$$2CO + O_{2}\rightarrow 2CO_{2}, \ \Delta H = -560KJ$$.

In this process, pressure changes from $$70\ atm$$ to $$40\ atm$$. Find out value of $$\Delta U$$ at $$500\ K$$.

[Given: gases deviates apprecially from ideal nature. $$1\ atm-litre = 0.1\ KJ$$].
  • $$-530\ KJ$$
  • $$-500\ KJ$$
  • $$-557\ KJ$$
  • $$-560\ KJ$$
The Born Haber cycle below represents the energy changes occurring at 298K when $$KH$$ is formed from its elements
v : $${ \Delta H }_{ atomisation }$$ $$K = 90 kJ/mol$$
w : $${ \Delta H }_{ ionisation }$$ $$K = 418 kJ/mol$$
x : $${ \Delta H }_{ dissociation }$$ $$H = 436 kJ/mol$$
y : $${ \Delta H }_{ electron affinity }$$ $$H = 78 kJ/mol$$
z : $${ \Delta H }_{ lattice }$$ $$KH = 710 kJ/mol$$
On complete reaction with water, $$0.1 g$$ of $$KH$$ gave a solution requiring 25 $${ cm }^{ 3 }$$ of 0.1M $$HCl$$ for neutralisation.Calculate the relative atomic mass of potassium from this information.
  • $$39$$
  • $$40$$
  • $$41$$
  • None of these
Write a balanced equation for the reaction of $$KH$$ with water.
  • $$KH + H_2O \rightarrow KOH + H_2O_2$$ 
  • $$KH + H_2O \rightarrow KOH + H_2$$ 
  • $$KH + H_2O \rightarrow K(OH)_2 + H_2$$ 
  • $$KH + H_2O \rightarrow KOH + H_2O$$ 
The amount of heat required to raise the temperature of a substance through 1$$^o$$C is called
  • thermal energy
  • calories
  • heat capacity
  • specific heat capacity
Hess's law is used to calculate
  • Enthalpy of reaction
  • Entropy of reaction
  • Work done in reaction
  • All of these
Which of the following type of energies are involved in Born Haber`s cycle ?
  • a. $$\Delta_{ sub }H$$
  • b. ionisation energy
  • c. bond dissociation energy
  • d. lattice energy
Specific heat capacity of lead is $$120\space J\space kg^{-1}\space K^{-1}$$. When $$7200J$$ of heat is supplied to $$5kg$$ of lead, the rise in temperature is
  • $$8^{\small\circ}C$$
  • $$10^{\small\circ}C$$
  • $$12^{\small\circ}C$$
  • $$14^{\small\circ}C$$
Gibbs- Helmholtz equation is:
  • $$\Delta G = T\Delta H + \Delta S$$
  • $$\Delta G = - T\Delta H - \Delta S$$
  • $$\Delta G = T\Delta H - \Delta S$$
  • $$\Delta G = -T\Delta H + \Delta S$$
A hypothetical reaction $$A \rightarrow 2B$$, proceeds through following sequence of steps:
(i) $$A \rightarrow C; \Delta H = q$$
(ii) $$C \rightarrow D; \Delta H = v$$
(iii) $$\dfrac{1}{2}D \rightarrow B; \Delta H = x$$
Then the heat of reaction is:
  • $$q - v + 2x$$
  • $$q + v - 2x$$
  • $$q + v + 2x$$
  • $$q + 2v - 2x$$
For the reaction, $$X_2Y_4(l) \longrightarrow 2XY_2(g)$$ at 300 K, the values of $$\Delta U$$ and $$\Delta S$$ are 2 kcal and 20 cal $$K^{-1}$$ respectively. The value of $$\Delta G$$ for the reaction is 
  • - 3400 cal
  • 3400 cal
  • - 2800 cal
  • 2000 cal
What wiII be the heat of formation of methane, if the heat of combustion of carbon is $$'-x' kJ$$, heat of formation of water is $$'-y' kJ$$ and heat of combustion of methane is $$'z' kJ$$?
  • $$(-x - y + z) kJ$$
  • $$(-z -x + 2y) kJ$$
  • $$(-x - 2y - z) kJ$$
  • $$(-x -2y + z) kJ$$
For the reaction of one mole of zinc dust with one mole of sulphuric acid in a bomb calorimeter, $$\triangle U$$ and $$w$$ corresponds to:
  • $$\triangle U < 0, w = 0$$
  • $$\triangle U < 0, w < 0$$
  • $$\triangle U > 0, w = 0$$
  • $$\triangle U > 0, w > 0$$
Mark the point where the temperature of $$H_2O$$ is changing at $$4.18 J/g^o$$C(or $$1$$ $$cal/g^oC$$)?
481442_fea501bda56042d9825a04db2e1ac4bd.png
  • A
  • B
  • C
  • D
  • E
From the following information given, determine $$\Delta H^o$$ for the decomposition of sodium chlorate?
$$NaClO_3(s)\rightarrow NaCl(s)+\displaystyle\frac{3}{2}O_2(g)$$
$$(\Delta H^o_f$$ values $$:$$ $$NaClO_3(s)=358J/mol,$$ $$NaCl(s)=-410j/mol$$, $$O_2(g)=0$$ $$kcal/mol)$$
  • $$52.0$$J
  • $$-52.0$$J
  • $$768$$J
  • $$-768$$J
  • $$\displaystyle\frac{3}{2}(-768J)$$
According to Hess's law, the heat of reaction depends upon
  • initial condition of reactants
  • initial and final conditions of reactants
  • intermediate path of the reaction
  • end conditions of reactants
If $$C+{O}_{2}.\longrightarrow  {CO}_{2}+94.2kcal$$
$${H}_{2}+\cfrac{1}{2}{O}_{2}\longrightarrow  {H}_{2}+68.3kcal$$
$${CH}_{4}+2{O}_{2}\longrightarrow  {CO}_{2}+2{H}_{2}O+210.8kcal$$
Then, the heat of formation of methane will be
  • $$47.3kcal$$
  • $$20.0kcal$$
  • $$45.9kcal$$
  • $$-47.3kcal$$
What is the characteristic of a material which undergo spontaneous combustion?
  • High calorific value
  • High vapour pressure
  • Low ignition temperature
  • All of the above
Statement 1 : Candles can be safely stored at room temperature, even though their reaction with air is spontaneous at room temperature.
Statement 2 : The reaction that takes place when a candle is burned involves a decrease in entropy.

  • Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  • Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  • Statement 1 is correct but Statement 2 is not correct.

  • Statement 1 is not correct but Statement 2 is  correct.

  • Both the Statement 1 and Statement 2 are not correct.

Which statement is correct about heat?
  • It is a measure of the transfer of energy due a temperature difference
  • The heat transfer is always from hot to cold
  • The heat absorbed by the surroundings equals the heat released by the system
  • The amount of heat lost or gained during a reaction is directly related to the enthalpy change of the reaction.
  • All answers are correct
Hess's Law is used
  • When a directly measured enthalpy change of reaction is not available
  • To calculate an enthalpy change value through multiple steps
  • Because enthalpy is a State Function
  • As an easy way to calculate the enthalpy change of a reaction
  • All of these options(A,B,C,D) are correct
If 100.0 J of energy is added to 50.0 g of Cu, initially at $$25.0^o C$$, what will be the final temperature? (Specific heat capacity = 0.382 J/ C.g )
  • $$31.2^o C$$
  • $$30.24^o C$$
  • $$25.2^o C$$
  • $$25.19^o C$$
  • $$19.8^o C$$
10 g of liquid at 300K is heated to 350 K. The liquid absorbs 6 kcals. What is the specific heat of the liquid (in $$cal/ \displaystyle { g }^{ \circ  }C$$)?
  • 6
  • 12
  • 60
  • 120
A spontaneous reaction occurs:
  • by itself and quickly
  • with outside intervention and quickly
  • by itself and slowly
  • with outside intervention and slowly
  • by itself but it has now effect on how fast the reaction takes
$$10\ g$$ of liquid at $$300\ K$$ are heated to $$350\ K$$. The liquid absorbs $$6\ kcal$$. What is the specific heat of the liquid (in $$cal/g^{\circ}C)$$?
  • $$6$$
  • $$12$$
  • $$60$$
  • $$120$$
  • $$600$$
Which set of the conditions given below guarantees that a reaction will be spontaneous?
  • $$\Delta H(+)$$ and $$\Delta S(-)$$
  • $$\Delta H(-)$$ and $$\Delta S(+)$$
  • $$\Delta H(+)$$ and $$\Delta S(+)$$ at low temperature
  • $$\Delta H(-)$$ and $$\Delta S(-)$$ at high temperature
  • $$\Delta G(+)$$
Heat required, to rise one unit mass of a substance by 1 degree Celsius, is known as  ......................... .
  • gibbs free energy
  • heat of formation
  • specific heat
  • Heinsenberg uncertainty principle
  • heat of vaporization
Determine the heat of reaction for the combustion of sulphur dioxide:

$$\displaystyle 2{ SO }_{ 2 }\left( g \right) +{ O }_{ 2 }\left( g \right) \rightarrow 2{ SO }_{ 3 }\left( g \right) $$

Given the following thermochemical equations:

I. $$\displaystyle { S }_{ 8 }\left( s \right) +8{ O }_{ 2 }\left( g \right) \rightarrow 8{ SO }_{ 2 }\left( g \right) \Delta H=-2374.6kJ$$
II. $$\displaystyle { S }_{ 8 }\left( s \right) +12{ O }_{ 2 }\left( g \right) \rightarrow 8{ SO }_{ 3 }\left( g \right) \Delta H=-3165.8kJ$$
  • -5540.4 kJ
  • -1385.1 kJ
  • -791.2 kJ
  • -197.8 kJ
  • -700 kJ
When one mole of sulfur burns to form $$SO_2$$, 1,300 calories are released. When one mole of sulfur burns to form $$SO_3$$, 3,600 calories are released. What is the $$\Delta H$$ when one mole of $$SO_2$$ is burned to form $$SO_3$$?
  • 3,900 cal
  • -1,950 cal
  • 1,000 cal
  • -500 cal
  • -2, 300 cal
$$\displaystyle S\left( s \right) +{ O }_{ 2 }\left( g \right) \rightarrow { SO }_{ 2 }\left( g \right) \quad \Delta { H }^{ \circ  }=-297kJ$$
$$\displaystyle 2{ SO }_{ 2 }\left( g \right) +{ O }_{ 2 }\left( g \right) \rightarrow 2{ SO }_{ 3 }\left( g \right) \quad \Delta { H }^{ \circ  }=-198kJ$$
Given the above thermochemical reactions, what is the heat of reaction for the formation of $$\displaystyle { SO }_{ 3 }\left( g \right) $$ provided below?
$$\displaystyle S\left( s \right) +{ 3/2O }_{ 2 }\left( g \right) \rightarrow { SO }_{ 3 }\left( g \right) $$
  • -495 kJ
  • -396 kJ
  • -198 kJ
  • +99
  • +198 kJ
Statement I
As ice absorbs heat and begins to melt, its temperature remains constant
Because
Statement II
Changes of state bring about changes in a substances potential energy, not in its kinetic energy
  • Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1
  • Both the Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.
  • Statement 1 is correct but Statement 2 is not correct.
  • Statement 1 is not correct but Statement 2 is correct.
  • Both the Statement 1 and Statement 2 are not correct.
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