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Assertion : The value of enthaply of ato...

Assertion : The value of enthaply of atomisation is maximum at about the middle of each series.
Reason : There is one uparied electron per d-orbital and this results in stronger interatomic interaction.

A

If both assetion and reason are true and the reason is the correct explanation of the assertion.

B

If both assertion and reason are ture but reason is not the correct explanation of the assertion.

C

If assertion is true but reason is false.

D

If assertion is false but reason is true.

Text Solution

Verified by Experts

The correct Answer is:
A
Greater the numbe of valence electrons, stronger is the resultant bonding and higher the enthalpy of atomisation.
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Assertion: The metals of 4d and 5d greater entalpies of atomisation than the corresponding elements of the 3d series. Reason: The metal-metal bond in 4d and 5d series are stronger than those in the 3d series.

Assertion : In transition elements radii of 5d series are virtually the same as those of the corresponding members of 4d series. Reason : The filling of 4f orbitals before 5d orbitals results in regular decrease in atomic radii.

Read the passage given below and answer the following questions: Within the 3d series, manganese exhibits oxidation states in aqueous solution from +2 to +7, ranging from Mn^(2+)(aq) to MnO_(4)^(-) (aq). Likewise, iron forms both Fe^(2+)(aq) and Fe^(3+)(aq) as well as the FeO_(4)^(2-) ion. Cr and Mn form oxyions CrO_(4)^(2-) , MnO_(4)^(-) , owing to their willingness to form multiple bonds . The pattern with the early transition metals-in the 3d series up to Mn, and for the 4d, 5d metals up to Ru and Os—is that the maximum oxidation state corresponds to the number of ‘‘outer shell’’ electrons. The highest oxidation states of the 3d metals may depend upon complex formation (e.g., the stabilization of Co^(3+) by ammonia) or upon the pH (thus MnO_(4)^(2-) (aq) is prone to disproportionation in acidic solution). Within the 3d series, there is considerable variation in relative stability of oxidation states, sometimes on moving from one metal to a neighbor, thus, for iron, Fe^(3+) is more stable than Fe^(2+) , especially in alkaline conditions, while the reverse is true for cobalt. The ability of transition metals to exhibit a wide range of oxidation states is marked with metals such as vanadium, where the standard potentials can be rather small, making a switch between states relatively easy. (Cotton, S. A. (2011). Lanthanides: Comparison to 3d metals. Encyclopedia of inorganic and Bioinorganic Chemistry.) In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage. Assertion: Highest oxidation state is exhibited by transition metal lying in the middle of the series. Reason: The highest oxidation state exhibited corresponds to number of (n-1)d electrons.

Read the passage given below and answer the following questions: In transition elements, generally, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d orbital each time the nuclear charge increases by unity. But the radii of the third (50) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction. Following are the transition metal ions of 3d series: Ti^(4+), V^(2+), Mn^(3+), Cr^(3+) (Atomic number: Ti = 22, V = 23, Mn = 25, Cr = 24) Assertion (A): Among the given ions, Mn^(3+) is the most strong oxidizing agent. Reason (R): Mn^(3+) has an unstable configuration.

A2Z-THE D AND F BLOCK ELEMENTS-Section B - Assertion Reasoning
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  3. Assertion : The value of enthaply of atomisation is maximum at about t...

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  4. Assertion: The spin only magnetic moment of Sc^(3+) is 1.73 BM. Reas...

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  5. Assertion : Hydrochloric acid is not used to acidify a KMnO(4) solutio...

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  6. Assertion : Solution of Na(2) CrO(4) in water is intensely electrons. ...

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  8. Assertion : Hyydroquinone is used as a developer for developing black ...

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  9. Assertion : The order of atomic radii of Cu, Ag and Au is Cu lt Ag ~~ ...

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  10. Assertion : 4d and 5d series elements have nearly same atomic radius. ...

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  11. Assertion: Tungsten has very high melting point. Reason: Tungsten is...

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  12. Assertion: Mn atom loses ns electrons first during ionisation as compa...

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  13. Assertion : CuSO(4).5H(2)O on heating to 250^(@)C losses all the five ...

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  14. Assertion : Silver chloride dissolves in execss ammonia. Reason : A...

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  15. Assertion : CrO(3) is an acid anhydride. Reason: CrO(3) is obtained ...

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  16. Assertion : Solid potassium dichromate gives greenish yellow vapour wi...

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  17. Assetion : Permanganate titrations is not carried out in presence of h...

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  18. The free gaseous Cr atom has six unpaired electrons. Half-filled s-o...

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  19. Assertion : K(2)CrO(4) has yellow colour due to charge transfer. Rea...

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  20. Assetion : The green manganate is paramagnetic but the pruple permanga...

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