The orange colour of dichromate solution changes to ____ on heating with an alkali due to the formation of ____ ions.
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d-and f-Block Elements - ISC Class 12 Chemistry Questions with Answers, Page 2
50 past-paper questions on d-and f-Block Elements from ISC Class 12 Chemistry papers (2027-2018), newest first, in full. Questions 21-40 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.
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An element [X] has an outer electronic configuration as $3d^5 4s^2$. The maximum oxidation state and most common oxidising state of the element will be:
- (a)+5, +3
- (b)+2, +2
- (c)+7, +3
- (d)+7, +2
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Assertion: The basic strength of hydroxides of lanthanoids decreases with an increase in their atomic number.
Reason: The size of trivalent cations of lanthanoids increases with an increase in their atomic number.
Given below are two statements marked Assertion and Reason. Read the two statements carefully and select the correct option.
- (a)Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
- (b)Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
- (c)Assertion is true and Reason is false.
- (d)Both Assertion and Reason are false.
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Choose the appropriate word(s) from the bracket [ethanol, [Fe(H2O)6]2+, anode, d2sp3, Cannizzaro, reducing, cathode, sp3d2, iodine, [Fe(CN)6]4-, methanol, aldol, oxidising, manganese dichloride]:
Since potassium permanganate is ____ in nature, it gives ____ on reaction with $\text{KI}$ solution in acidic medium.
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Halides of transition elements in higher oxidation states are more covalent. Give reason.
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Write equation for the following observations:
(a)
Potassium permanganate on reaction with potassium iodide in acidic medium releases iodine gas, water and the sulphates of potassium and manganese. Give the balanced equation for the reaction.
(b)
Potassium permanganate on reaction with oxalic acid in acidic medium gives salts of Potassium and Manganese along with water molecules and carbon dioxide gas. Give the complete and balanced equation.
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Give a reason for each of the following.
(i)[1.0]
Zinc, cadmium and mercury are considered as d-block elements but not regarded as transition elements.
(ii)[1.0]
Transition metals possess a great tendency to form complex compounds.
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(i)[1.0]
Give a reason to explain why transition metals can act as a good catalyst.
(ii)[1.0]
Scandium ($Z = 21$) does not exhibit variable oxidation states and yet it is regarded as transition element. Why?
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Account for the following:
(i)[1.0]
Salts of cuprous ($\text{Cu}^+$) ion are colourless whereas the salts of cupric ($\text{Cu}^{2+}$) ion are coloured.
(ii)[1.0]
Zinc is not regarded as a transition element. (at. no. of $\text{Zn} = 30$)
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Account for each of the following.
(i)[1.0]
Zirconium (Zr) and Hafnium (Hf) are difficult to separate.
(ii)[1.0]
Salts of Cupric ($\text{Cu}^{2+}$) ion are coloured whereas salts of Cuprous ($\text{Cu}^+$) ion are colourless.
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When $\text{KMnO}_4$ is heated with acidified oxalic acid, gas bubbles are evolved. These gas bubbles are evolved due to the formation of:
- (a)$\text{SO}_2$
- (b)$\text{CO}_2$
- (c)$\text{SO}_3$
- (d)$\text{O}_2$
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(i)[1.0]
Why is $\text{Mn}^{2+}$ ion more stable than $\text{Fe}^{2+}$ ion?
(Atomic number of $\text{Mn} = 25$ and $\text{Fe} = 26$)
(ii)[1.0]
Trivalent Lanthanoid ions such as $\text{La}^{3+}$ ($Z = 57$) and $\text{Lu}^{3+}$ ($Z = 71$) do not show any colour in their solution. Give a reason.
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Give a reason for each of the following:
(i)[1.0]
The size of the trivalent cations in Lanthanoid series decreases steadily as the atomic number increases.
(ii)[1.0]
The third ionization energy of manganese ($Z = 25$) is unexpectedly high.
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Acidified $\text{K}_2\text{Cr}_2\text{O}_7$ solution turns green when $\text{Na}_2\text{SO}_3$ is added to it. This is due to formation of:
- (a)$\text{CrO}_4^{2-}$
- (b)$\text{Cr}_2(\text{SO}_3)_3$
- (c)$\text{Cr}_2\text{O}_3$
- (d)$\text{Cr}_2(\text{SO}_4)_3$
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Give reason for the following:
(i)[1.0]
Transition metals form large number of complex compounds.
(ii)[1.0]
Transition elements show variable oxidation states.
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Complete and balance the following chemical equations:
(i)[1.0]
$\text{KMnO}_4 + \text{H}_2\text{SO}_4 + \text{FeSO}_4 \longrightarrow$ ____ + ____ + ____ + ____
(ii)[1.0]
$\text{K}_2\text{Cr}_2\text{O}_7 + \text{KI} + \text{H}_2\text{SO}_4 \longrightarrow$ ____ + ____ + ____ + ____
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State a reason for each of the following:
(i)[1.0]
$\text{La(OH)}_3$ is more basic than $\text{Lu(OH)}_3$.
(ii)[1.0]
Transition elements and their compounds act as catalyst.
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Complete and balance the following chemical equations:
(i)[1.0]
$\text{KMnO}_4 + \text{H}_2\text{SO}_4 + \text{KI} \rightarrow$ ____ + ____ + ____ + ____
(ii)[1.0]
$\text{K}_2\text{Cr}_2\text{O}_7 + \text{H}_2\text{SO}_4 + \text{H}_2\text{S} \rightarrow$ ____ + ____ + ____ + ____
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Select and write the correct alternative from the choices given below:
(i)[1.0]
An alkyl isocyanide on complete reduction gives:
- (a)Primary amine.
- (b)Secondary amine.
- (c)Tertiary amine.
- (d)Carboxylic acid.
(ii)[1.0]
For a spontaneous reaction $E^\circ_{\text{cell}}$ and $\Delta G^\circ$ will be respectively:
- (a)-ve and -ve
- (b)-ve and +ve
- (c)+ve and -ve
- (d)+ve and +ve
(iii)[1.0]
Which of the following pairs of transition elements have exceptional electronic configuration?
- (a)Sc and Cu
- (b)Fe and Ni
- (c)Cr and Cu
- (d)Mn and Zn
(iv)[1.0]
For a first order reaction, when $100\text{ g}$ of the reactant is taken, $75\text{ g}$ of the reactant reacts in 8 minutes. If $200\text{ g}$ of the same reactant is taken, in how much time $150\text{ g}$ of the reactant will react?
- (a)8 minutes
- (b)16 minutes
- (c)20 minutes
- (d)24 minutes.
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Why are $\text{Zn}$, $\text{Cd}$ and $\text{Hg}$ not regarded as transition elements?
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