Question

Class 12 Chemistry  MCQ Questions of The d-and f-Block Elements with Answers?

Answer 1

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1. Shape of d-orbital is

(a) spherical
(b) dumb bell
(c) double dumb bell
(d) none of these

2. Electronic configuration of alkaline earth element is

(a) ns²
(b) ns¹
(c) np⁶
(d) ns⁰

3. Lanthanoid contraction is due to increase in

(a) atomic number
(b) effective nuclear charge
(c) atomic radius
(d) valence electrons

4. Which one of the following is diamagnetic ion?

(a) Co²⁺
(b) Ni²⁺
(c) Cu²⁺
(d) Zn²⁺

5. 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-t/transition
(d) d-d transition

6. 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

7. In which of the following pairs of ions, the lower oxidation state in aqueous solution is more stable than the other?

(a) Ti⁺, Ti³⁺
(b) Cu⁺, Cu³⁺
(c) Cr²+, Cr³⁺
(d) V²+, VO²⁺ (V⁴)

8. 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

9. Malachite is an ore of 

(a) Silver
(b) Mercury
(c) Magnesium
(d) Copper

10. The chief ore of Hg is

(a) Pyrolusite
(b) Bauxite
(c) Galena
(d) Cinnabar

11. The transition element which shows the highest oxidation state is: 

(a) Iron
(b) Vanadium
(c) Manganese
(d) Chromium

12. Gun metal is

(a) Cu + Zn
(b) Cu + Sn + Zn
(c) Cu + Sn
(d) Zn + Sn

13. German silver is an alloy of:

(a) Fe, Cr, Ni
(b) Ag, Cu Au
(c) Cu, Zn, Ni
(d) Cu, Zn, Sn

14. The composition of duralumin is

(a) Al 94%, Mg 6%
(b) Cu 56%, Zn 24%, Ni 20%
(c) Cu 95%, Al 5%
(d) Al 95%, Cu 4%, Mn 0.5%, Mg 0.5%

15. Which of the following is not an ore of iron?

(a) limonite
(b) Cassiterite
(c) magnetite
(d) none of these

16. Lanthanide for which +II and +III oxidation states are common is

(a) La
(b) Pr
(c) Ce
(d) Eu

17. F₂ is formed by reacting K₂MnF₆ with

(a) SbF₅
(b) MnF₃
(c) KSbF₆
(d) MnF₄

18. Which of the following radioisotopes is used as anticancerous?

(a) Na -24
(b) C -14
(c) U -235
(d) Co -60

19. The colour of copper sulphide is

(a) Blue
(b) Black
(c) Red
(d) Green

20. What is wrong about transition metals?

(a) Diamagnetic
(b) Paramagnetic
(c) Form complexes
(d) Shows variable oxidation state

21. The last electron in d-block elements goes to

(a) (n-1) d
(b) nd
(c) np
(d) (n-1) s

22. The elements which exhibit both vertical and horizontal similarities are

(a) inert gas elements
(b) representative elements
(c) rare elements
(d) transition elements

23. An atom has electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s² in which group would it be placed?

(a) Fifth
(b) Fifteenth
(c) Second
(d) Third

24. Number of unpaired electrons in Ni²⁺ (Z = 28) is

(a) 4
(b) 2
(c) 6
(d) 8

25. Transition metals usually exhibit highest oxidation states in their

(a) chlorides
(b) fluorides
(c) bromides
(d) iodides

Answer 2

1. Answer : (c) double dumb bell

Explanation: The ml values for five d orbitals are -2, -1, 0, +1, and +2 i.e., we can say d-subshell has five orientations. All these d-orbitals have the same energy and are called degenerate orbitals. Hence, we can say d-orbitals have double dumbbell-shaped.

2. Answer : (a) ns²

Explanation: The general electronic configuration of alkaline earth elements is ns². These elements have two valence electrons in the outermost s shell.

3. Answer : (b) effective nuclear charge

Explanation: Lanthanoid contraction effect results from poor shielding of nuclear charge (nuclear attractive force on electrons) by 4f electrons so effective nuclear charge increases; the 6s electrons are drawn towards the nucleus, thus resulting in a smaller atomic radius.

4. Answer : (d) Zn²⁺

Explanation: Zn²⁺ = [Ne 3s² 3p⁶ 4s⁰ 3d¹⁰]  It is diamagnetic, so no unpaired e⁻s.

5. Answer : (d) d-d transition

Explanation: Colour of transition metal ions are due to absorption of the same wavelength. This results in d−d transition.

6. Answer : (b) Cu >Au > Ag

Explanation: Hence the melting point decreases from copper to silver, but the melting point of gold becomes even higher than silver due to its higher density that happened due to contraction.

7. Answer : (a) Ti⁺, Ti³⁺

Explanation: Ti⁺ ions are more stable than Ti³⁺ and thus, Ti³⁺ ions change to Ti⁺ ions thereby acting as oxidising agents.

8. Answer : (b) lanthanoid contraction

Explanation: Zr and Hf have almost similar atomic and ionic radii it can be explained on the basis of shielding effect . Due to lanthanide contraction. Moreover, the electrons which are present in inner shells, shields outer electrons from nuclear charge, after that they experience a low effective nuclear charge.

9. Answer : (d) Copper

Explanation: Malachite, a minor ore but a widespread mineral of copper, basic copper carbonate, Cu₂CO₃(OH)₂. Because of its distinctive bright green colour and its presence in the weathered zone of nearly all copper deposits, malachite serves as a prospecting guide for that metal.

10. Answer : (d) Cinnabar

Explanation: Cinnabar is an ore of mercury.

11. Answer : (c) Manganese

Explanation: Manganese has the highest oxidation state because the number of unpaired electrons in the outermost shell is more, i.e. 3d⁵ 4s².

12. Answer : (b) Cu + Sn + Zn

Explanation: Gunmetal, also called G Metal, variety of bronze, formerly used for ordnance. Modern admiralty gunmetal is composed of 88 percent copper, 10 percent tin, and 2 percent zinc and is used for gears and bearings that are to be subjected to heavy loads and low speeds.

13. Answer : (c) Cu, Zn, Ni

Explanation: German Silver is an alloy of copper, zinc and nickel, sometimes also containing lead and tin.

14. Answer : (d) Al 95%, Cu 4%, Mn 0.5%, Mg 0.5%

Explanation: Duralumin is an alloy 95% aluminium, 4% copper, 0.5% manganese and 0.5% magnesium.

15. Answer : (b) Cassiterite

Explanation: Cassiterite was the main tin ore throughout ancient history and remains the most important source of tin today. Thus we can say that cassiterite isn't an ore of iron.

16. Answer : (d) Eu

Explanation: Lanthanides show variable oxidation states. The most stable oxidation state of Lanthanides is +3. They also show +2 and +4 oxidation states due to the presence of either half filled or completely filled or empty 4f sub shell. Due to stable half filled configuration Eu shows +2 configuration.

17. Answer : (a) SbF₅

Explanation: F₂ is the formed by reacting K₂MnF₆ with Sb₅. Reaction is as follows:

K₂MnF₆ + 2SbF₅ → 2KSbF₆ + MnF₃ + \(\frac{1}{2}\)F₂

18. Answer : (d) Co -60

Explanation: Co-60 is used as anti-cancerous among the given radioactive isotopes. It emits \(\beta\)− particles and energetic gamma rays, for which reason it is used in radiation therapy. 

19. Answer : (b) Black

Explanation: When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution.

20. Answer : (a) Diamagnetic

Explanation: Transition elements have one or more unpaired electrons. Due to the presence of these unpaired electrons, they show paramagnetism. Thus, transition metals are not diamagnetic. They are good conductors of heat and electricity. They form complexes and show variable oxidation state as d orbitals are gradually filled up in the transition series.

21. Answer : (a) (n-1) d

Explanation: In these elements, the last electron enters the d orbital of the penultimate shell i.e. the last electron goes to (n-1) d orbital. Hence these elements are named as d-block elements.

22. Answer : (d) transition elements

Explanation: Elements which exhibit both vertical and horizontal similarities are transition elements. They show vertical similarity because of same electronic configuration. They show horizontal similarity because of similar size.

23. Answer : (a) Fifth

Explanation: The outermost shell and one shell prior to it in d subshell, has total 5 electron so it will be placed in fifth group in transition element or 'd' block of periodic table.

24. Answer : (b) 2

Explanation: Nickel has two unpaired electrons in the 3d sublevel. When nickel ionizes to the +2 state it loses the two electrons in the 4s, so there are still two unpaired electrons in Ni²⁺.

25. Answer : (b) fluorides

Explanation: The highest oxidation states of transition metals are shown by fluorides and oxides as fluorine and oxygen are the most electronegative elements. The highest oxidation state shown by any transition metal is +8.

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