Chemistry Test 136

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Chemistry Test 136

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Weekly Quiz Competition

Question 1
4 / -1

Consider the following reaction

A
Internal energy of formation of product in the reaction A is more

B
Internal energy of product in the reaction B is more

C
Cyclic ethers are more thermodynamically stable

D
Entropy decrease is less in reaction B

Solution

Enthalpy is not a conclusive measurement of whether a reaction will be more spontaneous and favorable. Entropy is.
Taking a look at both reactions, in reaction A two molecules are combining and giving one molecule and in reaction B only one molecule is giving one molecule so decrease in entropy in reaction B is less. So, ∆S will be less negative in here hence more favorable.
ΔG = ΔH-TΔS
Question 2
4 / -1

Which of the following will not produce nitrogen gas?

A
Heating of (NH₄)₂Cr₂O₇

B
NH₃ reacting with Br₂ in aqueous solution

C
NH₃ reacting with CuO

D
Ca reacting with NH₃

Solution

a) (NH₄)₂Cr₂0₇→ N₂ + Cr₂O₃ +4H₂O
b) 8NH₃ + 3Br₂→N₂ + 6NH₄Br
c) 2NH₃ + 3CuO →N₂ + 3Cu + 3H₂O
d) 3Ca + 6NH₃→3[Ca(NH₂)₆]
Question 3
4 / -1

The hydride ion H^- has the same electron configuration as helium but is much less stable. Which of the following option explains the given statement

A
Size of hydride ion is small

B
Single positive charge on the proton must now control the 2 electrons

C
Helium is noble gas hence it is more stable and more reactive

D
All of these

Solution

Hydrogen ₁H : 1S¹

Hydride: ₁H^- :1S²

Helium ₂He : 1S²

Helium has two proton in it and it can stabilize 2 electrons. But, in hydrogen as one more electron enters and it becomes hydride ion, now one proton has to account for two electrons, the stability is affected. In hydride one proton cannot stabilize two electrons so structural deformity arises which leads to its reactivity.
Question 4
4 / -1

IUPAC name of the following compound is

A
2,7-dimethyl-3,5-octadiyne-2,7-diol

B
2,7-methyl-3,5-dioctadyine-2,7-diol

C
2,7-dimethyl-3,5-octa-2,7-diol-3,5-diyne

D
2,7-dihydroxy-2,7dimethyl-3,5-octadiyne

Solution

IUPAC name of the compound will be
2,7-dimethyl-3,5-octadiyne-2,7-diol
Question 5
4 / -1

XeF₂ when dissolved in water produces three compound A, B, C. A is inert. Compound B forms strongest H-bond with its anion and exists as D. Compound C is used in combustion. Which of the following is correct?

A
A is XeO₃

B
B is F₂

C
C is Xe

D
D is HF₂^-

Solution

Reaction mentioned is given as below
2XeF₂ +2H₂O →2Xe + 4HF + O₂
HF forms H-bond with F^- and exists as HF₂^-
Question 6
4 / -1

Which of the marked position is most susceptible to nucleophilic attack

A
a and b

B
b and c

C
c and a

D
a, b and c all are equally suceptible

Solution

Position a and c will be more susceptible to nucleophilic attack

Position a has bromine attached to it making it electron deficient or more electropositive and hence inviting for nucleophile

Position c has oxygen atom attached to it. High electronegativity of oxygen makes carbon highly electropositive and susceptible to nucleophilic attack.
Question 7
4 / -1

Ester and amide are found in equilibrium which of the following is true regarding the equilibrium of following. K₁ and K₂ are equilibrium constants

A
K₁ > K₂ in acidic solution medium

B
K₁ > K₂ in basic solution medium

C
K₁ > K₂ irrespective of medium

D
None of these

Solution

1.As we increase the acidic conditions amine will be protonated and equilibrium will shift backward hence K₁>K₂

2. In basic medium phenol will be deprotonated and hence reaction will shift forward here K₂>K₁
Question 8
4 / -1

In the given reaction, the major product will be

A

B

C
Both will be equally formed

D
None of these

Solution

E₂ eliminations therefore take place from the anti-periplanar conformation.

Here, E₂ elimination gives mainly one of two possible stereoisomers.

2-Bromobutane has two conformations with H and Br anti-periplanar, but the one that is less hindered leads to more of the product, and the E-alkene predominates.

Another way to understand will be in any alkene formation major product is always most stable alkene. We can see alkene given in option a is trans alkene and in option b is cis alkene. Trans alkene being more stable on account of less steric repulsion will be major product.
Question 9
4 / -1

Arrhenius relation is described as K= A e^-Ea/RT which of the following statement is correct regarding activation energy

A
Lower activation energy reactions are more susceptible to temperature change

B
Higher activation energy reactions are more susceptible to temperature change

C
Activation energy is thermo dynamical concept while rate is kinetic concept both are fundamentally different

D
Activation energy is of reaction is independent from temperature.

Solution

Here we can see that on increasing temperature those reaction having high value of E_a will be more susceptible to change in rate.
Question 10
4 / -1

Which of the following is correct about acidic nature of boric acid?

A
It shows Brosnted acidity

B
It is a strong acid due to hydrogen bond present in its crystalline structure

C
Its acidity is enhanced in presence of cis-diols like glycerols

D
All of the above.

Solution

a) B(OH)₃ +2 H₂O →B(OH)₄^- +H₃O⁺
This reaction is characterized as Lewis Acidity of boric acid

b) Due to hydrogen bond present in crystalline structure it becomes difficult for it to donate H+ and hence acidic character decreases.

c) B(OH)₃ +2 H₂O →B(OH)₄^- +H₃O⁺
Cis-diols form complex with borate ion and shift the equation forward hence ionizing the boric acid to higher extent. And acidic character increases.