Irregular trend in the standard reduction potential value of the first row transition elements is due to

1

(a)

regular variation of first and second row enthalpies

(b)

irregular variation of sublimation ethalpies

(c)

regular variation of sublimation ethalpies

(d)

increase in number of unpaired electrons

Which of the following ixidation states is the most common among the lanthanoids ?

1

(a)

4

(b)

2

(c)

5

(d)

3

Which of the following statement about transition elements is incorrect ?

1

(a)

They show variable oxidation states

(b)

All the ions are coloured

(c)

They exhibit diamagnetic and paramagnetic properties

(d)

They exhibit catalytic property

KMnO₄, oxidation number of Mn is

1

(a)

+ 2

(b)

+ 4

(c)

+ 6

(d)

+ 7

Name a member of lanthanide series which is well known to exhibit + 4 oxidation state :

1

(a)

Ce

(b)

La

(c)

Lu

(d)

Pr

Electronic configuration of a transition element X in +3 oxidation state is [Ar] 3d⁵. What is its atomic number ?

1

(a)

25

(b)

26

(c)

27

(d)

24

Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid state ?

1

(a)

Ag₂SO₄

(b)

CuF₂

(c)

ZnF₂

(d)

Cu₂CI₂

The magnetic nature of elements depends on the presence of unpaired electrons, Identify the configuration of transition element, which shows highest magnetic moment.

1

(a)

3d⁷

(b)

3d⁵

(c)

3d⁸

(d)

3d²

Which of the following statements is not correct ?

1

(a)

Copper liberates hydrogen from acids

(b)

In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine

(c)

Mn³⁺ and Co³⁺ are oxidising agents in aqueous solution

(d)

Ti²⁺ and Cr²⁺ are reducing agents in aqueous solution

Highest oxidation state of manganese in fluoride is +4 (MnF₄) but highest oxidation state in oxides is +7 (Mn₂O₇ ) because ............ .

1

(a)

fluorine is more electronegative than oxygen

(b)

fluorine does not possess d - orbitals

(c)

fluorine stabilise lower oxidation state

(d)

in covalent compounds, fluorine can form single bond only while oxygen forms double bond

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

1

(a)

It is because of poor shielding of 4f and 5f electrons in actinoids whereas in lanthanoids, there is poor shielding effect of 4f electrons only, that is why effective nuclear charge increases more from element to element in actinoids than lanthanoids.

Which trivalent cation is largest in the lanthanoid series?

1

(a)

La³⁺ is largest in lanthanoid series.

A substance is found to have a magnetic moment of 3.9 B.M. How many unpaired electrons does it contain ?

1

(a)

Using the formula, \(\mu =\sqrt { n(n+2) } B.M.,n=3\)

Why are transition elements known as d - block elements?

1

(a)

Transition elements are called d - block elements because the last electron enters (n - 1) d - orbital, i.e., d - orbital of the penultimate shell.

Predict which of the following will be coloured in aqueous solution. Ti³⁺, V³⁺, Cu⁺, Sc³⁺, Mn²⁺, Fe³⁺ and Co^2+. Give reason for each.

3

(a)

Write complete chemical equations for:
(i) Oxidation of Fe²⁺ by Cr₂O₇^2- in acid medium.
(ii) Oxidation of S₂O₃^2- by MnO₄^- in neutral aqueous medium. 

3

(a)

How would you account for the following:
(i) With the same \(d\)-orbital configuration \((d^{ 4 })Cr^{ 2+ }\) is a reducing agent while \(Mn^{ 3+ }\) is an oxidizing agent.
(ii) The actinoids exhibit a larger number of oxidation states than the corresponding members in the lanthanoid series.
(iii) Most of the transition metal ions exhibit characteristic in colours in aqueous solutions.

4

(a)

A mixed oxide of iron and chromium, FeO. Cr₂O₃ , is fused with sodium carbonate in presence of air to form a yellow coloured compound (A). On acidification, the compound (A) forms an orange coloured compound (B) which is a strong oxidizing agent. Identify
(i) the compounds (A) and (B) 
(ii) Write balanced chemical equations for each step.

4

(a)

Compare the stability of +2 oxidation state for the elements of the first transition series.

4

(a)

(a) Given below are the electrode potential values, E^o for the some of the first row of transition elements:

Element	EoM2+/M (V)
V(23)  Cr(24) Mn(25) Fe(26) Co(27) Ni(28) Cu(29)	-1.18 -0.91 -1.18 -0.44 -0.28 -0.25 +0.34

Explain the irregularities in these values on the basis of electronic structures of atoms.
(b) Complete the following reaction equations:
(i) Cr₂O₇^2-+Sn²⁺+H⁺\(\longrightarrow \) 
(ii) MnO₄^-+Fe²⁺+H⁺\(\longrightarrow \)

6

(a)

The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

6

(a)