Advertisements
Advertisements
प्रश्न
Which is a stronger reducing agent, Cr2+ or Fe2+ and why?
Advertisements
उत्तर
Cr2+ is a stronger reducing agent than Fe2+. In the formation of Cr2+ to Cr3+, the change is d4 to d3, but in the formation of Fe2+ to Fe3+, the change is d6 to d5. In a medium like water, d3 is more stable than d5.
APPEARS IN
संबंधित प्रश्न
Account for the following:
Cu+ ion is unstable in aqueous solution.
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomization of zinc is the lowest, i.e., 126 kJ mol−1. Why?
The \[\ce{E^{\circ}_{(M^{2+}/M)}}\] value for copper is positive (+0.34 V). What is possible reason for this? (Hint: consider its high ΔaH° and low ΔhydH°)
Explain why Cu+ ion is not stable in aqueous solutions?
Explain briefly how +2 state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?
What are alloys?
What can be inferred from the magnetic moment value of the following complex species?
| Example | Magnetic Moment (BM) |
| K2[MnCl4] | 5.9 |
An antifriction alloy made up of antimony with tin and copper, which is extensively used in machine bearings is called _______.
(A) Duralumin
(B) Babbitt metal
(C) Spiegeleisen
(D) Amalgam
NF3 is possible, but NF5 is not. Why?
The transition metals show _________ character because of the presence of unpaired· electrons and Cu+ is ____________ because of its electronic configuration is [Ar]3d10
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
Transition metals with lowest melting point is ______.
Match the properties given in Column I with the metals given in Column II.
| Column I (Property) | Column II (Metal) | |
| (i) | Element with highest second ionisation enthalpy |
(a) \[\ce{Co}\] |
| (ii) | Element with highest third ionisation enthalpy |
(b) \[\ce{Cr}\] |
| (iii) | \[\ce{M}\] in \[\ce{M(CO)6}\] is | (c) \[\ce{Cu}\] |
| (iv) | Element with highest heat of atomisation |
(d) \[\ce{Zn}\] |
| (e) \[\ce{Ni}\] |
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
Which of the following transition metal is not coloured?
Account for the following:
Ce4+ is a strong oxidising agent.
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
Give a reason for the following:
Zinc, cadmium and mercury are considered as d-block elements but not regarded as transition elements.
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
