Chemistry Test 154

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Chemistry Test 154

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Weekly Quiz Competition

Question 1
4 / -1

Select the incorrect statement among following:

A
Ce⁺⁴ can act as good oxidizing agent

B
Fe³⁺/Fe²⁺ redox couple has more positive electrode potential than Mn³⁺/Mn²⁺ couple.

C
Of the d⁴ species Cr²⁺ is strongly reducing while manganese(III) is strongly oxidising.

D
Cobalt(II) is stable in aqueous solution but in the presence of strong field i.e. complexing reagents it is easily oxidised.

Solution

(A) Because of E° = +1.74 V for Ce⁺⁴ to Ce⁺³

(B) Due to stability of half filled d–orbitals, Mn²⁺ is more stable than Mn³⁺ and thus its reduction is more spontaneous. Similarly Fe³⁺ is more stable than Fe²⁺ and thus its reduction is less spontaneous.

(D) Co²⁺ is stable in aqueous solution because it get surrounded and weakly bonded to water molecules. In presence of strong ligands and air it gets oxidised to Co(III) as strong ligands get co–ordinated more strongly with Co(III). The electronic configuration of Co(II) and Co(III).
Question 2
4 / -1

Li + → (P)

(Q) + 2H₂O → Ca(OH)₂+ 2H₂

2NaBH₄+ I₂ → (R) + 2NaI + H₂

If equal masses of (P), (Q) and (R) treated with water, which will give more amount of H₂ ?

A
P

B
Q

C
R

D
All are equal

Solution
Question 3
4 / -1

Directions For Questions

The element Sulphur exists in many allotropes and each allotrope often exists in polymorphs having different crystal parameters i.e., axial lengths and angles (a, b, c, α, β, γ). Then consider the reaction for different crystal of Sulphur :

(i) S(a ≠ b ≠ c, α = β = γ = 90°) +  → SO₃(g),   ΔH₁
(ii) S(a ≠ b ≠ c, α = γ, β ≠ 90°) +   → SO₃(g),  ΔH₂

(iii) S(a ≠ b ≠ c, α = β = γ = 90°) + O₃(g) → SO₃(g),   ΔH₃

(iv) S(a ≠ b ≠ c, α = γ, β ≠ 90°) + O₃(g) → SO₃(g), ΔH₄

...view full instructions

Select incorrect option (only magnitude comparision).

A
ΔH₁ < ΔH₂ < ΔH₄

B
ΔH₁ < ΔH₃ < ΔH₄

C
ΔH₁ < ΔH₂ > ΔH₃ < ΔH₄

D
ΔH₁ + ΔH₄ = ΔH₂ + ΔH₃

Solution

Rhombic sulphur is more thermodynamically stable than monoclinic sulphur and also oxygen is more stable than ozone.

   ∴  ΔH₁ < ΔH₂ > ΔH₃ < ΔH₄
Question 4
4 / -1

Which of the following is INCORRECT order for boiling points for unknowns (P), (Q), (R), (S), (T), (U) & (V). In the reaction sequence:

A
(P) > (V)

B
(Q) > (R)

C
(T) > (P)

D
(T) > (U)

Solution

(P) = H₂O, (Q) = CCl₄, (R) = SiCl₄, (S) = H₂,

(T) = NH₃, (U) = AsH₃, (V) = HF,

(X) = CH₄ & (Y) = Cl₂
Question 5
4 / -1

Directions For Questions

CF₃I + NaOH → A + B

...view full instructions

Find the correct statement.

A
A > C (Boiling point)

B
A < C (Vapour pressure)

C
A > C (Melting point)

D
A > C (Dipole moment)

Solution

A = CHF₃, B = NaOI, C = CHI₃,

D = HCOONa, P = CH₃OH, Q = NaI
Question 6
4 / -1

Moles of CO₂ evolved during given reaction per mol?

A
5

B
4

C
6

D
7
Question 7
4 / -1

Which of the following compound is most harmful component of phtochemical smog?

A
NO₂

B
PAN

C
SO₂

D
CH₃NO₂

Solution

PAN– peroxy acetyl nitrate is most harmful.
Question 8
4 / -1

Some aqueous solutions are given below. Find the solution whose pH changes maximum by adding 10 millimoles amount of pure H₂SO₄.

A
100 mL, 0.1 M HCl + 100 mL, 0.5 M Ca(OH)₂

B
100 mL, 0.1 M Ca(OH)₂ + 100 mL, 0.4 M H₂S

C
100 mL, 0.1 M NaOH + 100 mL, 0.2 M K₂SO₄

D
100 mL, 0.5 M CH₃COOH + 100 mL, 0.1 M Ba(OH)₂

Solution

(A) Initially, mms of OH^-  = 100 ,
  mms of H⁺ = 10, [OH^-] = 90/200
⇒ pOH=0.346
Finally, mms of OH^- = 100,
ms of H⁺ = 30, [OH^-] = 70/200
   ⇒ pOH=0.456
So, change in pH = 0.111 (small change)

(B) After initial reaction,
  mms of HS^- = 20, mms of H₂S = 20
  (its a buffer of HS^–/H₂S)
   So, change in pH will be very small.

(C) Initially, mms of OH^- = 10,
mms of H⁺ = 0, [OH^–] = 10/200
   ⇒ pH=12.7
   Finally, mms of OH^- = 10,
mms of H⁺ = 20, [H⁺] = 10/200
  ⇒ pH=1.3
   So, change in pH = 11.4 (very large)

(D) Initially, mms of AcOH = 30,
  mms of AcO^- = 20,
mms of H₂S = 20 (its a buffer)
So, change in pH will be very small.
Question 9
4 / -1

For a 3s–orbital. Find the maximum distance for radial node.

A

B

C

D

Solution

Radial node occurs where probability of finding e^– is zero.
Question 10
4 / -1

Packing fraction of NaCl unit cell [assuming ideal] if ions along one of its body diagonal are absent (Cl^– forms FCC, r₊ & r_– are radius of cation and anion)

A

B

C

D