Karnataka Board PUCPUC Science 2nd PUC Class 12

Account for the Following: Mn Shows the Highest Oxidation State of +7 with Oxygen but with Fluorine, It Shows Oxidation State of +4. - Chemistry


Account for the following:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.

Give reasons:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows the highest oxidation state of +4.


Solution 1

In case of oxygen, Mn shows the highest oxidation state of +7. This is because Mn forms pπ–dπ multiple bonds using 2p orbitals of oxygen and 3d orbitals of Mn. With F, Mn displays an oxidation state of +4 because of the single bond formation caused by the unavailability of 2p orbitals in F for multiple bonding.

Solution 2

Mn shows the highest oxidation state of +7 with oxygen because it can form ppi−dpi multiple bonds using 2p orbital of oxygen and 3d orbital of Mn. On the other hand, Mn shows the highest oxidation state of +4 with flourine because it can form single bond only.

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2015-2016 (March) All India Set 2 C


Why is Sc3+ colourless while Ti3+ coloured? (Atomic number Sc = 21, Ti =22)

Why do interstitial compounds have higher melting points than corresponding pure metals?

Explain why is Fe3+ more stable than Fe2+?

How would you account for the following? 

Transition metals exhibit variable oxidation states.


Calculate magnetic moment of  `Fe_((aq))^(2+) ion (Z=26).`

Why +2 oxidation state of manganese is more stable?

Why do the transition elements have higher enthalpies of atomisation?

How would you account for the following: Transition metals form complex compounds.

Account for the following :

Zn is not considered as a transition element.

Out of Mn3+ and Cr3+, which is more paramagnetic and why ?

(Atomic nos. : Mn = 25, Cr = 24)

In the series Sc (= 21) to Zn (= 30), the enthalpy of atomization of zinc is the lowest, i.e., 126 kJ mol−1. Why?

The Eθ(M2+/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high ΔaHθ and low ΔhydHθ)

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

How would you account for the following:

Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.

Give examples and suggest reasons for the following features of the transition metal chemistry:

 The highest oxidation state is exhibited in oxoanions of a metal.

What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.

Write down the number of 3d electrons in each of the following ions:

Ti2+, V2+, Cr3+, Mn2+, Fe2+, Fe3+, CO2+, Ni2+ and Cu2+.

Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

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

Write the factors which are related to the colour of transition metal ions.

Which one of the following ions is coloured?

NF3 is possible, but NF5 is not. Why?

How would you account for the following? 

Transition metals and their compounds act as catalysts.

Write balanced chemical equations for the conversion of `CrO_4^(2-)` to `Cr_2O_7^(2-)` in acidic medium and `Cr_2O_7^(2-)` to `CrO_4^(2-)`
 in basic medium.

Why does the density of transition elements increase from Titanium to Copper? (at. no. Ti = 22,
Cu = 29)

Dissociation of H2S is suppressed in acidic medium.

Why do transition metal ions possess a great tendency to form complexes?

The paramagnetic character in-3d-transition series elements increases-: up to Mn and then decreases.

How is potassium dichromate prepared from chrome iron ore?

Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.

Explain why transition elements form alloys.

Explain why Zn2+ salts are white whereas Cu2+ salts are coloured.

Explain why transition metals and their compounds act as a catalyst.

Explain why:
(i) Mn2+ is more stable than Fe2+ towards oxidation to +3 state.
(At. no. of Mn = 25, Fe = 26)

(ii) Transition elements usually form coloured ions.

(iii) Zr and Hf exhibit similar properties.
(At. no. of Zr = 40, Hf = 72)

Give reasons for the following:
The transition metals generally form coloured compounds.

Why is \[\ce{HCl}\] not used to make the medium acidic in oxidation reactions of \[\ce{KMnO4}\] in acidic medium?

Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?

(i) \[\ce{Co^{2+}}\]

(ii) \[\ce{Cr^{2+}}\]

(iii) \[\ce{Mn^{2+}}\]

(iv) \[\ce{Cr^{3+}}\]

The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?

Match the properties given in Column I with the metals given in Column II.

  Column I (Property) Column II (Metal)
(i)  An element which can show +8 oxidation state (a) \[\ce{Mn}\]
(ii)  3d block element that can show (b) \[\ce{Cr}\]
  upto +7 oxidation state (c) \[\ce{Os}\]
(iii)  3d block element with highest melting point (d) \[\ce{Fe}\]

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.

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

(activation energy, Threshold energy, increased, lowered, partially, full, d-d transition, Benzoic acid, benzaldehyde)

Only those transition metal ions will be coloured which have ______ filled d-orbitals facilitating ______.

If enthalpies of formation of C2H4(g), CO2(g) and H2O(l) at 25°C and 1 atm pressure are 52, – 394 and – 286 kJ/mol respectively, the change in ethalpy for combustion of C2H4 is equal to

The orientation of an atomic orbital is governed by

Catalytic hydrogenation of benzene gives

The standard electrode potentials of four elements A, B, C and D are – 3.05, – 1.66, – 0.40 and + 0.80. The highest chemical reactivity will be exhibited by

Which does not belong to first transition series?

Sodium this sulphate is used in photography because of its:-

Mercury is the only metal liquid at room temperature due to its:-

Which one of the following characters tie of the transition metal is associated with higher catalytic activity?

Which of the following ions will exhibit colour in aqueous solution?

Which of the following transition metal is not coloured?

Match List - I with List - II

List - I List - II
(a) \[\ce{[Fe(CN)6]^3-}\] (i) 5.92 BM
(b) \[\ce{[Fe(H2O)6]^3+}\] (ii) 0 BM
(c) \[\ce{[Fe(CN)6]^4-}\] (iii) 4.90 BM
(d) \[\ce{[Fe(H2O)6]^2+}\] (iv) 1.73 BM

Choose the correct answer from the options given below.

Match List - I with List - II.

List - I List - II
(a) \[\ce{[Fe(CN)6]^3-}\] (i) 5.92 BM
(b) \[\ce{[Fe(H2O)6]^3+}\] (ii) 0 BM
(c) \[\ce{[Fe(CN)6]^4-}\] (iii) 4.90 BM
(d) \[\ce{[Fe(H2O)6]^2+}\] (iv) 1.73 BM

Choose the correct answer from the options given below.

The number of terminal oxygen atoms present in the product B obtained from the following reactions is:

\[\ce{FeCr2O4 + Na2CO3 + O2 -> A + Fe2O3 + CO2}\]

\[\ce{A + H^+ -> B + H2O + Na^+}\]

The electrode potential of M2+/M of 3d-series elements shows the positive value for ______.

The value of Δ0 for \[\ce{RhCl^{3-}6}\] is 243 KJ/mol which wavelength of light will promote an electron from. The colour of the complex is ______.

Which of the following ions acts as a typical transition metal ion?

Consider the following standard electrode potentials (E° in volts) in aqueous solution:

Element M3+/M M+/M
Al - 1.66 +0.55
Tl + 1.26 -0.34

Based on these data, which of the following statements is correct?

In the ground state of atomic Fe (Z = 26), the spin-only magnetic moment is ______ × 10-1 BM.
(Round off to the nearest integer).

[Given: `sqrt3 = 1.73, sqrt2 = 1.41`]

The disproportionation of \[\ce{MnO^{2-}_4}\] in acidic medium resulted in the formation of two manganese compounds A and B. If the oxidation state of Mn in B is smaller than that of A, then the spin-only magnetic moment (µ) value of B in BM is ______. (Nearest integer)

Assertion (A): Transition metals have high enthalpy of atomisation.

Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.

The given graph shows the trends in melting points of transition metals:

Explain the reason why Cr has the highest melting point and manganese (Mn) has a lower melting point.

A pair of coloured ions is ______.

Explain the magnetic properties of d-block (or transition) elements.

Explain the use of different transition metals as catalysts.

The compounds of Ti4+ ions are colourless due to ______.


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