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Science (English Medium) Class 12 - CBSE Important Questions

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Why do the transition elements have higher enthalpies of atomisation?

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Complete the following equation:

\[\ce{2MnO4- + 6H+ + 5NO2- ->}\]

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

What are the consequences of lanthanoid contraction?

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Lanthanoids

Write the formula of an oxo-anion of Chromium (Cr) in which it shows the oxidation state equal to its group number

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Account for the following: 

Zn, Cd and Hg are soft metals.

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Lanthanoids

Following are the transition metal ions of 3d series:

Ti4+, V2+, Mn3+, Cr3+

(Atomic numbers: Ti = 22, V = 23, Mn = 25, Cr = 24)

Answer the following:

1) Which ion is most stable in an aqueous solution and why?

2) Which ion is a strong oxidising agent and why?

3) Which ion is colourless and why?

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Complete the following equations:

`2MnO_4^(-)+16H^++5S^(2-)rarr`

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

How would you account for the following? 

Zr (Z = 40) and Hf (Z = 72) have almost identical radii.

 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

How would you account the following :

Highest fluoride of Mn is MnF4 whereas the highest oxide is Mn2O7.

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Actinoids

Complete the following equation :

\[3 {MnO}_4^{2 -} + 4 H^+ \to\]
Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

Account for the following : 
Manganese shows maximum number of oxidation states in 3d series. 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

E0 value for  Mn3+ Mn2+ couple is much more positive than that for Cr3-/ Cr2-.

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

 Write the chemical equation for the preparation of 4 KMnO from 2. MnO Why does purple colour of acidified permanganate solution decolourise when it oxidises Fe2- to Fe3+

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

Account for the following : 
 Ti4+ is colourless whereas V4+  is coloured in an aqueous solutions. 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Why do transition metals exhibit higher enthalpy of atomization? 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Name an element of lanthanoid series which is well knwon to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent? 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Lanthanoids

What is lanthanoid contraction? Write the.............

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Lanthanoids

 Write the ionic equation showing the oxidation of Fe(II) salt by acidified dichromate solutions. 

Appears in 1 question paper
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements
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