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201.	Amongest the following the lowest degree of paramagnetism per mole of the compound at `298K` will be shown by:A. `MnSO_(4).4H_(2)O`B. `CuSO_(4).5H_(2)O`C. `FeSO_(4).6H_(2)O`D. `NiSO_(4).6H_(2)O`
Answer» Correct Answer - B

202.	Which of the following transition metal ions has the lowest density?A. CopperB. NickelC. ScandiumD. Zinc
Answer» Correct Answer - C (A)=8.95 , (B)=8.95, (C )=3.0 , (D) =7.14 Across the period atomic volume decrease upto copper due poor shielding of d-orbital electrons and addition of extra electrons in inner orbital and then increase inZinc due to interelectronic repulsion in completely filled d-and s-orbitals. Consequently densities increase from Sc to Cu and then decreases in Zn.

203.	Of the ions `Zn^(2+),Ni^(2+) and Cr^(3+)` (atomic number Zn=30,Ni=28,Cr=24):A. Only `Zn^(2+)` is colourless and `Ni^(2+) and Cr^(3+)` are coloured.B. all three are colourless.C. all three are colouredD. only `Ni^(2+)` is coloured and `Zn^(2+)` and `Cr^(3+)` are colourless.
Answer» Correct Answer - A Valence shell electron configuration of `._30Zn^(+2)` is `3d^(10)4s^(0)`. As there is no unpaired electrons for d-electrons for d-d transition the solution of ion will be colourless. Valence shell electron configuration of `._28^(2+) is 3d^(8) 4s^(0)` . As there 2 unpaired electrons , there is d-d transition of electrons , so the solution of ion will be coloured. Valence shell electrons configuration of `._24Cr^(3+) is 3d^(3) 4s^(0)` . As there are 3 unpaired , there is d-d transition of electrons, so the solution of ions will be coloured.

204.	`CuSO_(4)` solution reacts with excess of KCN solution to form:-A. `Cu(CN)_(2)`B. `CuCN`C. `K_(2)[Cu(CN)_(2)]`D. `K_(3)[Cu(CN)_(4)]`
Answer» Correct Answer - D

205.	The number of moles of `KMnO_(4)` that will be needed to react completely with one mole of ferrous oxalate in acidic solution is:A. `3//5`B. `2//5`C. `4//5`D. `1`
Answer» Correct Answer - A `6KMnO_(4)+10FeC_(2)O_(4)+24H_(2)SO_(4)to3K_(2)SO_(4)+6MnSO_(4)+5Fe_(2)(SO_(4))_(3)+20CO_(2)+24H_(2)O`. ` therefore 3/5 "mole"` of `KMnO_(4)` for one mole ferrous oxalate.

206.	The number of moles of `KMn_(4)` that will be needed to react with one mole of sulphite ion in acidic medium isA. `2//5`B. `3//5`C. `4//5`D. `1`
Answer» Correct Answer - A `2MnO_(4)^(-)+5SO_(3)^(2-)+6H^(+) to2Mn^(2+)+5SO_(4)^(2-)+3H_(2)O`. therefore2/5mole of `MnO_(4)^(-)` for one mole` SO_(3)^(2-)`.

207.	Across the lanthanide series , the basicity of the lanthanoide hydroxides:A. increasesB. decreasesC. first increases and then decreasesD. does not change
Answer» Correct Answer - B Across lanthanoide series basicity of lanthanoide hydroxide decreases.

208.	The most common lanthanoide is :A. LanthanumB. CeriumC. SamariumD. Plutonium
Answer» Correct Answer - B Lanthanum =d-block element. Cerium= lanthanoide element & samarium, plutonium =actinoide element.

209.	Among the lanthanides the one obtained by synthetic method isA. `Lu`B. `Pm`C. `Pr`D. `Gd`
Answer» Correct Answer - B

210.	The number of d-electrons retained in `Fe^(2+)` (At. No. Fe=26)` ions are:A. `3`B. `4`C. `5`D. `6`
Answer» Correct Answer - 4 `Fe_(26)-[Ar]3d^(6)4s^(2)` `Fe^(2+)_(24"electrons")-[Ar]3d^(6)4s^(0)`

211.	The radius of `La^(3+)(Z=57)` is 106 pm. Which one of the following given values will be closest to the radius of `Lu^(3+)(Z=71)`?A. `1.60Å`B. `1.40Å`C. `1.06Å`D. `0.85Å`
Answer» Correct Answer - 4 Due to lanthanide contraction there occurs net decrease in size. Only one `0.85Å` is similar one . SO radius of `Lu_(71)^(3+)` will be closest to `0.85Å`

212.	The lanthanide contraction is responsible for the fact thatA. `Zr` and `Y` have about the same radiusB. `Zr` and `Nb` have similar oxidation stateC. `Zr` and `Hf` have about the same radiusD. `Zr` and `Ce` have the same oxidation state.
Answer» Correct Answer - C Due to poor shielding of `(n-2)` f-electrons, size of `Zr` and `Hf` remain same.

213.	The lanthanide contraction is responsible for the fact thatA. `Zr` and `Y` have about the same radiusB. `Zr` and `Nb` have similar oxidation stateC. `Zr` and `Hf` have about the same radiusD. `Zr and Ce` have same oxidation state.
Answer» Correct Answer - 3 The atomic radii of the second and third transition series are almost the same . 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 which essentially compensates for the expected increase in atomic size with increasing atomic number . The net result of the lanthanoid contraction is that second and third d series exhibit similar radii `(e.g.,Zr 160)` pm, `Hf 159 pm)`

214.	Which of the following factors may be regarded as the main cause of lanthanide contraction?A. Greater shielding of `5d` electrons by `4f` electronsB. Poorer shielding of `5d` electron by `4f` electronsC. Effective shielding of one of `4f` electrons by another in the sub-shell.D. Poor shielding of one `4f` electrons by another in the sub -shell.
Answer» Correct Answer - 4 Lanthanide contraction is due to poor shielding of one of `4 f` enectron by another in the sub-shell.

215.	Give reasons for each of the following: (i) Size of trivalent lanthanoid cation decrease with increase in the atomic number. (ii) Transition metal fluorides are ionic in nature whereas bromides and chlorides are usualy covalent in nature. (iii) Chemistry of all the lanthanoids is quite similar.
Answer» Correct Answer - (i) Cause of lanthanide contraction. (ii) As electronegativity of halogens decreases in the order `FgtClgtBr`, By , the ionic character of transition metal haldies decrease in the order `M-FgtM-ClgtM-Br`. Hence , fluorides are ionic whereas chloride and bromides are covalent. (iii) The change in the size of the lanthanoids due to lanthanoid contraction is very small as we produceed from `La(Z=57)` to `Lu(Z=71)`. Hence , their chemical properties are similar . Moreover, their valence shell configuration remains the same because the electrons are added into the inner `4` f-subshell. hence , they show similar chemical properties .

216.	Assertion : `K_(2)CrO_(4)` has yellow colour due to charge transfer. Reason : `CrO_(4)^(2-)` ion is tetrahedral in shape.A. Statement-1 is true , Statement-2 is true and Statement-2 is correct explanation for Statement-1B. Statement-1 is true, Statement-2 is True and Statement-2 is Not correct explanation for statement-1C. Statement-1 is true, Statement-2 is FalseD. Statement-1 is False, Statement-2 is True
Answer» Correct Answer - B

217.	Write all posible oxidation state of an element having atomic number `25`.
Answer» Correct Answer - `E.C of ._25Mn=[Ar]^(18) 3d^(5) 4s^(0)`. It shows oxidation states of `+2,+3,+4,+5, +6 and +7`.

218.	Among the following statement choose the true or false statements(s). `K_(2)Cr_(2)O_(7)`on heating with charcoal gives mettalic potassium and `Cr_(2)O_(3)` on heating in current of `H_(2)` the crystalline `KMnO_(4)` is converted into `KOH` and `Mn_(3)O_(4)` Hydrated ferric chloride on treatment with `2-2`-dimethoxypropane gives anhydrous ferric chloride.
Answer» Correct Answer - (a) False (b) False (C ) True `K_(2)Cr_(2)O_(7)+2C(charcoal)undersettoDelta Cr_(2)+K_(2)CO_(3)+COuparrow`. `2KMnO_(4)+5H_(2)undersettoDelta2KOH+2MnO+4H_(2)O` `FeCl_(3).6H_(2)O+6-CHunderset(OCH_(3))underset(\|)overset(OCH_(3))overset(\|)(C)-CH_(3) to ("anhydrous")+12CH_(3)OH+6CH_(3)COOH_(3)`.

219.	How iron `(III)` catalyses the reaction between iodide & persulphate ?
Answer» `{:(2Fe^(3+)+2I^(-),to,2Fe^(2+),+I_(2)),(2Fe^(2+)+S_(2)O_(8)^(2-),to,2Fe^(3+),2SO_(4)^(2-)),(2I^(-)+S_(2)O_(8)^(2-),overset(Fe(III))to,I_(2),+2SO_(4)^(2-)):}`

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