Bihar Board 12th Chemistry Objective Answers Chapter 8 The d-and f-Block Elements

Bihar Board 12th Chemistry Objective Questions and Answers

Bihar Board 12th Chemistry Objective Answers Chapter 8 The d-and f-Block Elements

Question 1.
General electronic configuration of transition metals is
(a) (n – 1)d ^1–10 ns²
(b) nd¹⁰ ns²
(c) (n-1)d¹⁰ ns²
(d) (n- 1) d^1-5 ns²
Answer:
(a) (n – 1)d ^1–10 ns²

Question 2.
Which one of the following is a ‘d-block element’?
(a) Gd
(b) Hs
(c) Es
(d) Cs
Answer:
(b) Hs

Question 3.
Which of the following pairs of ions have the same electronic configuration ?
(a) Cu²⁺,Cr²⁺
(b) Fe³⁺ , Mn²⁺
(c) CO³⁺,Ni³⁺
(d) Sc³⁺,Cr³⁺
Answer:
(b) Fe³⁺ , Mn²⁺

Question 4.
The melting points of Cu, Ag and Au follow the order
(a) Cu > Ag > Au
(b) Cu > Au > Ag
(c) Au>Ag>Cu
(d) Ag>Au>Cu
Answer:
(b) Cu > Au > Ag

Question 5.
Zr and Hf have almost equal atomic and ionic radii because of …………….
(a) diagonal relationship
(b) lanthanoid contraction
(c) actinoid contraction
(d) belonging to the same group
Answer:
(b) lanthanoid contraction

Question 6.
Reactivity of transition elements decreases almost regularly from Sc to Cu because of
(a) lanthanoid contraction
(b) regular increase in ionisation enthalpy
(c) regular decrease in ionisation enthalpy
(d) increase in number of oxidation states.
Answer:
(b) regular increase in ionisation enthalpy

Question 7.
Identify the species in which the metal atom is in +6 oxidation state
(a) MnC>4
(b) [Cr(CN)₆]^3-
(c) [NiF₆]^2-
(d) CrO₂Cl₂
Answer:
(d) CrO₂Cl₂

Question 8.
In which of the following compounds manganese has oxidation number equal to that of iodine in KIO₄ ?
(a) Potassium manganate
(b) Potassium permanganate
(c) Manganous chloride
(d) Manganese chloride
Answer:
(b) Potassium permanganate

Question 9.
The correct order of E°m²⁺/m values with negative sign for the four successive elements Cr, Mn, Fe and Co is
(a) Fe > Mn > Cr > Co
(b) Cr > Mn > Fe > Co
(c) Mn>Cr>Fe>Co
(d) Cr>Fe>Mn>Co
Answer:
(c) Mn>Cr>Fe>Co

Question 10.
Which of the following d-block element has half-filled penultimate as well as valence subshell ?
(a) Cu
(b) Au
(c) Ag
(d) Cr
Answer:
(d) Cr

Question 11.
Fe³⁺ compounds are more stable than Fe²⁺ compounds because
(a) Fe³⁺ has smaller size than Fe²⁺
(b) Fe³⁺ has 3d⁵ configuration (half-filled)
(c) Fe³⁺ has higher oxidation state
(d) Fe³⁺ is paramagnetic in nature
Answer:
(b) Fe³⁺ has 3d⁵ configuration (half-filled)

Question 12.
The salts of Cu in +1 oxidation state are unstable because
(a) Cu⁺ has 3d¹⁰ configuration
(b) Cu⁺ disproportiontates easily to Cu(O) and Cu²⁺
(c) Cu⁺ disproportionates easily to Cu²⁺ and Cu³⁺
(d) Cu⁺ is easily reduced to Cu³⁺
Answer:
(b) Fe³⁺ has 3d⁵ configuration (half-filled)

Question 13.
Which of the following transition metal ions has highest magnetic moment ?
(a) Cu²⁺
(b) Ni²⁺
(c)CO²⁺
(d) Fe²⁺
Answer:
(d) Fe²⁺

Question 14.
The correct order of number of unpaired electrons is
(a) Cu²⁺ > Ni²⁺ > Cr³⁺ > Fe³⁺
(b) Ni²⁺ > Cu²⁺ > Fe³⁺ > Cr³⁺
(c) Fe³⁺ > Cr³⁺ > Ni²⁺ > Cu²⁺
(d) Cr³⁺ > Fe³⁺>Ni²⁺ > Cu²⁺
Answer:
(c) Fe³⁺ > Cr³⁺ > Ni²⁺ > Cu²⁺

Question 15.
The magnetic moment of a divalent ion in aqueous solution with atomic number 25 is ………….
(a) 9 B.M
(b) 2.9 B.M
(c) 6.9 B.M
(d) 9.9 B.M
Answer:
(a) 9 B.M

Question 16.
Which of the following transition metal ions is colourless ?
(a) V²⁺
(b) Cr³⁺
(c) Zn²⁺
(d) Ti³⁺
Answer:
(c) Zn²⁺

Question 17.
Which of the following compounds is not coloured ?
(a) Na₂ [CuCl₄ ]
(b) Na₂ [CdCl₄ ]
(c) K₄[Fe(CN)₆]
(d)  K₃[Fe(CN)₆]
Answer:
(b) Na₂ [CdCl₄ ]

Question 18.
Compound that is both paramagnetic and coloured is
(a) K₂Cr₂O₇
(b)  (NH₄)₂[TiCl₆]
(c) VOSO₄
(d) K₃[Cu(CN)₄]
Answer:
(c) VOSO₄

Question 19.
Most of the transition metals exhibit
(i) paramagnetic behaviour
(ii) diamagnetic behaviour
(iii) variable oxidation states
(iv) formation of coloured ions
(a) (ii), (iii) and (iv)
(b) (i), (iii) and (iv)
(c) (i), (ii) and (iii)
(d) (i), (ii) and (iv)
Answer:
(b) (i), (iii) and (iv)

Question 20.
For Zn²⁺, Ni²⁺, Cu²⁺ and Cr²⁺ which of the following statement is correct ?
(a) Only Zn²⁺ is colourless and Ni²⁺, Cu²⁺ and Cr²⁺ are coloured
(b) All the ions are coloured
(c) All the ions are colourless
(d) Zn²⁺ and Cu²⁺ are colourless while Ni²⁺ and Cr²⁺ are coloured
Answer:
(a) Only Zn²⁺ is colourless and Ni²⁺, Cu²⁺ and Cr²⁺ are coloured

Question 21.
Colour of transition metal ions are due to absorption of some wavelength. This results in
(a) d-s transition
(b) s-s transition
(c) s-d transition
(d) d-d transition
Answer:
(d) d-d transition

Question 22.
Transition elements form binary compounds with halogens. Which of the following elements will form MF₃ type compounds ?
(a) Cr
(b) Cu
(c) Ni
(d) All of these
Answer:
(a) Cr

Question 23.
Which of the following is not an amphoteric ion
(a) AI³⁺
(b)Cr³⁺
(c) Fe²⁺
(d) Zn²⁺
Answer:
(c) Fe²⁺

Question 24.
Which of the following are basic oxides ? Mn₂O₇, V₂O₃, V₂O_s, CrO, Cr₂O₃
(a) Mn₂O₇ and V₂O₃
(b) V₂O₃ and CrO
(c) CrO and Cr₂O₃
(d) V₂O₅ and V₂O₃
Answer:
(b) V₂O₃ and CrO

Question 25.
V₂O_s reacts with alkalies as well as acids to give
(a) \(\mathrm{VO}_{4}^{3-} \text { and } \mathrm{V} \mathrm{O}^{2+}\)
(b) \( \mathrm{V} \mathrm{O}^{2+} \text { and } \mathrm{VO}_{4}^{+}\)
(c) \(\mathrm{VO}_{2}^{+} \text {and } \mathrm{V} \mathrm{O}^{2+}\)
(d) \(\mathrm{VO}_{4}^{3-} \text { and } \mathrm{VO}_{4}^{+}\)
Answer:
(d) \(\mathrm{VO}_{4}^{3-} \text { and } \mathrm{VO}_{4}^{+}\)

Question 26.
Which of the following compounds is used as the starting material for the preparation of potassium dichromate ?
(a) K₂SO₄.Cr₂.(SO₄)₃24H₂O (Chromealum)
(b) PbCrO₄ (Chromite yellow)
(c) FeCr₂O₄ (Chromite)
(d) PbCrO₄.PbO (Chrome red)
Answer:
(c) FeCr₂O₄ (Chromite)

Question 27.
What happens when potassium iodide reacts with acidic solution of potassium dichromate ?
(a) It liberates iodine
(b) Potassium sulphate is formed
(c) Chromium sulphate is formed
(d) All the above products are formed
Answer:
(d) All the above products are formed

Question 28.
One mole of acidified K₂Cr₂O₇ on reaction with excess KI will liberate_____ mole(s) of I₂
(a) 3
(b) 1
(c)7
(d) 2
Answer:
(a) 3

Question 29.
What would happen when a solution of potassium chromate is treated with an excess of dilute nitric acids ?
(a) Cr³⁺ and Cr₂O^2- are formed
(b) Cr₂O^2- and H₂O and formed
(c) CrO_4^– is reduced to +3 state of Cr
(d) CrO^2- is oxidised to +7 state of Cr
Answer:
(b) Cr₂O^2- and H₂O and formed

Question 30.
In the dichromate anion (Cr₂O^2-),
(a) all Cr-0 bonds are equivalent
(b) 6 Cr – O bonds are equivalent
(c) 3 Cr – O bonds are equivalent
(d) no bonds in Cr₂O^2- are equivalent
Answer:
(b) 6 Cr – O bonds are equivalent

Question 31.
When MnO₂ is fused with KOH and O₂, what is the product formed and it colour ?
MnO₂ + KOH + O₂ → ? + H₂O
(a) MnO – colourless
(b) KMnO₄ – purple
(c) K₂MnO₄ – dark green
(d) MnO₃ – black
Answer:
(c) K₂MnO₄ – dark green

Question 32.
The equation
\(3 \mathrm{MnO}_{4}^{2-}+4 \mathrm{H}^{+} \rightarrow 2 \mathrm{MnO}_{4}^{-}+\mathrm{MnO}_{2}+2 \mathrm{H}_{2} \mathrm{O} \) represents
(a) reduction
(b) disproportionation
(c) oxidation in acidic medium
(d) reduction in acidic medium
Answer:
(b) disproportionation

Question 33.
The number of moles of KMnO₄ that are needed to react completely with one mole of ferrous oxalate in acidic solution is
(a) 3/5
(b) 2/5
(c) 4/5
(d) 1
Answer:
(a) 3/5

1 mole of KMnO₄ accepts 5 electrons
1 mole of ferrous oxalate loses 3 electrons
5e⁺ = 1mole of KMnO₄ 3e^–will be equivalent to 3/5 mole of KMnO₄

Question 34.
Which of the following is correct representation of reaction of acidified permanganate solution with sulphurous acid

Answer:
(a)

Question 35.
The most common lanthanoid is
(a) lanthanum
(b) cerium
(c) samarium
(d) plutonium
Answer:
(a) lanthanum

Question 36.
Which is the non-lanthanide element ?
(a) La
(b) Lu
(c) Pr
(d) Pm
Answer:
(a) La

Question 37.
The correct configuration of f-block elements is
(a) (n – 2)f ^1-14 (n-1)d ^0-1 ns²
(b) (n – 1) f ^1-14(n-1)d ^0-1 ns²
(c) (n – 3) f ^1-14(n-2)d ^0-1 (n-1)s²
(d) (n – 2)f ^0-1 (n-1)d ^0-1 ns²
Answer:
(a) (n – 2)f ^1-14 (n-1)d ^0-1 ns²

Question 38.
Lanthanoid contraction is due to increase in
(a) atomic number
(b) effective nuclear charge
(c) atomic radius
(d) valence electrons
Answer:
(b) effective nuclear charge

Question 39.
The correct order of ionic radii of Ce, La, Pm and Yb in +3 oxidation state is
(a) La³⁺< Pm³⁺< Ce³⁺< Yb³⁺
(b) Yb³⁺<Pm³⁺< Ce³⁺< La³⁺
(c) La³⁺< Ce³⁺< Pm³⁺< Yb³⁺
(d) Yb³⁺< Ce³⁺< Pm³⁺< La³⁺
Answer:
(b) Yb³⁺<Pm³⁺< Ce³⁺< La³⁺