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Chemistry (Engineering Entrance)

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Which of the following is NOT the characteristic of equilibrium?

  1. Dynamic in nature

  2. Non-spontaneous

  3. Reversible

  4. Thermodynamic compromise


Correct Option: B
Explanation:

This option is correct because equilibrium is always spontaneous. Being spontaneous means that the reaction proceeds with any external help or external driving force such as temperature of pressure.

What is the relationship of equilibrium constant K and reaction quotient Q at equilibrium?

  1. K < Q

  2. K > Q

  3. K = Q

  4. None of these


Correct Option: C
Explanation:

This option is correct as at equilibrium the concentration of reactant and products are constant for a particular set of reactants and products and reaction quotient is equal to equilibrium constant of the reaction.

Which of the following expressions represents the equilibrium constant for the following redox reaction?

Cu2+(aq) + Zn(s) -------> Zn2+(aq) + Cu(s)

  1. [Zn2+][Cu]/[Cu2+][Zn]

  2. [Cu2+][Zn]/[Zn2+][Cu]

  3. [Cu2+]/[Zn2+]

  4. [Zn2+]/[Cu2+]


Correct Option: D
Explanation:

This option is correct because while the formula for equilibrium constant it is generalized as K = [products]/[reactants] ………………..where the concentration of pure reactants and products is taken to be unity.In the given reaction the concentration of reactant Zn(s) and product Cu(s) is to be taken unity and hence we will get the correct answer as K = [Zn2+]/[Cu2+]

For which of the following reactions is Kp equal to Kc?

  1. H2(g) + I2(g) <------> 2HI(g)

  2. 2C(s) + O2(g) <------> 2CO(g)

  3. N2(g) + 3H2(g) <------> 2NH3(g)

  4. CaCO3(s) <------> CaO(s) + CO2(g)


Correct Option: A
Explanation:

The relation between Kp and Kc is given as Kp = Kc(RT)∆ng………………∆ng is the difference between the number of moles of gaseous products and reactants.For this reaction ∆ng is 0. Hence Kp = Kc. Hence this is the correct answer.

Consider a reaction I2(s) --------> I2 (in solution). How will the equilibrium shift on addition of more I2(s)?

  1. Equilibrium shifts in forward direction

  2. Equilibrium shifts in backward direction

  3. No change in equilibrium takes place.

  4. Equilibrium shift cannot be predicted


Correct Option: C
Explanation:

This option is correct because I2 is a solid and amount of solid present is not important as long as any equilibrium is present.

If K1, K2 be the equilibrium constants of two individual reactions and K3 is the equilibrium constant of a reaction obtained by addition of these two reactions, then correct relation between K1, K2 and K3 will be

  1. K3 = K1/K2

  2. K1 = K3/K2

  3. K1 = K2.K3

  4. K2 = K1.K3


Correct Option: B
Explanation:

This option is correct as the given option may be written as K3  =  K1.K2And when two reactions are added to give the third reaction then equilibrium constant of the third reaction is always the product of the equilibrium constant of the individual reactions. 

For the reaction given below, identify the type of graph obtained between [Ba2+] and [SO42-].

BaSO4(s) <------> Ba2+(aq) + SO42-(aq)

  1. Straight line graph, ( y = mx + c ) type

  2. Rectangular Hyperbola

  3. Constant graph ( y = 0) type

  4. None of these


Correct Option: B
Explanation:

This option is correct and can be explained as follows: For the give n reaction the equilibrium constant is given byK = [Ba2+][SO42-]……………………….or we can say that [Ba2+] and [SO42-] are having inversely proportional relationship whose graph is given by a rectangular hyperbola.

For the reaction N2(g) + 3H2(g) <--------> 2NH3(g), the correct relation between Kp and Kc will be

  1. Kp = Kc

  2. Kp = Kc (RT)

  3. Kp = Kc (RT)2

  4. Kp = Kc/(RT)2


Correct Option: D
Explanation:

The relation between Kp and Kc is given as Kp = Kc(RT)∆ng………………∆ng is the difference between the number of moles of gaseous products and reactants.For the given reaction ∆ng is -2. Hence Kp = Kc(RT)-2. Hence this is the correct answer.

Consider a reaction for which enthalpy change (∆H0) is zero. The equilibrium constant will

  1. increase on increasing temperature

  2. decrease on increasing temperature

  3. first decrease then increase on increasing temperature

  4. be independent of temperature.


Correct Option: D
Explanation:

This option is correct because for a reaction having enthalpy change zero is independent of change of temperature and favors neither formation of products or reactants.

For the equilibrium established between butane and isobutane, if the volume of the container is halved, the equilibrium will

  1. shift in forward direction

  2. not change

  3. shift in backward direction

  4. shift randomly


Correct Option: B
Explanation:

This option is correct and can be explained as follows: The equilibrium constant for the reaction in the given question is given ask  =  [Butane]/[Isobutane].   However on decreasing the volume of the container the individual concentration of butane and isobutane increases but the overall change in equilibrium constant will be zero as the increase in concentrations of reactant and products will be cancelled.

Enthalpy change(∆H0) for the reaction is given to be +181 kJmol-1 On increasing the temperature,

  1. more nitric oxide will be formed

  2. nitric oxide will dissociates to give nitrogen and oxygen.

  3. equilibrium will be maintained

  4. None of these


Correct Option: A
Explanation:

This option is correct and can be explained as follows: Since ∆H0 for the reaction is +ve which means that reaction is endothermic in nature. Hence when temperature is increased then according to Le Chatelier's Principle it favors the forward reaction which nullifies the effect of increase in temperature hence, more nitric oxide is formed.

Which of the following is an example of homogenous equilibrium?

  1. Ca(OH)2(s) + H2O(aq) ⇌ Ca2+(aq) + 2OH- (aq)

  2. Ag2O(s) + 2HNO3(aq) ⇌ 2AgNO3(aq) + H2O(l)

  3. Fe3+(aq) + SCN-(aq) ⇌ Fe(SCN)2+(aq)

  4. Ni(s) + 4CO(g) ⇌ Ni(CO)4(g)


Correct Option: C
Explanation:

This answer is correct because all the reactants and products are in the aqueous phase hence, represent homogenous equilibria.

Consider a solution saturated with Ag2SO4(s) at equilibrium Ag2SO4(s) ⇌ 2Ag+(aq) + SO42-(aq) On addition of NaCl(s), the amount of Ag2SO4 in equilibrium will

  1. increase

  2. decrease

  3. first decrease then increase

  4. remains constant.


Correct Option: B
Explanation:

This option is correct and can be explained as follows: When NaCl(s) is added to the system it dissociates as NaCl(s)    Na+(aq)  +  Cl-(aq)The Cl- ions obtained from the dissociation of solid NaCl will combine with Ag+ ions to precipitate AgCl. Hence the equilibrium will be shifted in forward direction in accordance with Le-Chatelier's principle and more Ag+ and SO42- ions will be formed resulting in consumption of Ag2SO4 and hence its concentration will decrease.

Directions: The following question has four choices out of which ONLY ONE is correct.

The effect of the change in external conditions on the chemical equilibrium is given by

  1. Le- Chatelier’s principle

  2. Hardy Shulze Rule

  3. Markovnikov's Rule

  4. Sequence Rule


Correct Option: A
Explanation:

This is the correct answer because the external effects on equilibrium were given by chemist Henry Louis Le Chatelier. Hence it is called Le Chatelier’s principle. According to Le Chatelier’s Principle when a system is subjected to any disturbance in its equilibrium state then equilibrium is shifted in the direction where the effect of the change in external condition is minimized.

How many peroxide linkages are present in S2O8-2?

  1. 1

  2. 2

  3. 3

  4. 5


Correct Option: A
Explanation:

This option is correct because , S2O8-2, is a dimerize form of  SO4-2 in which one O - atom of each sulphate ion link together to form dimer and that linkage is peroxide linkage and  only one linkage is persent in this ion.  

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