NEET Chemistry The d and f Block Elements Questions Solved


CuSO4 (aq.)H2SMof KCNExcessN+O

Then final products N and O are respectively.

(a) [Cu(CN)4]3-,(CN)2

(b) CuCn,(CN)2

(c) [Cu(CN)4]2-,(CN)2

(d) Cu(CN)2,K2S

(a) CuSO4(aq.)H2S    2CuS        excessKCN[Cu(CN)4]3-+(CN)2

                             Black ppr.(M)                  (N)               (O)

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CrO42- (yellow) changes to Cr2O72- (orange) in pH =x and vice versa in pH=y. Hence, x and y are:

(a) 6,8

(b) 6,5

(c) 8,6

(d) 7,7

(a) 2CrO42-+ 2H+Cr2O72-+H2O

     Cr2O72-+2OH-2CrO42-+H2O

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When steam is passed over red hot iron , the substances formed are:

(a) Fe2O3 +H2

(b) Fe3O4 +H2

(c) FeO +H2

(d) FeO+ H2 +O2

 

 

Iron does not react with water in the ordinary temperature. It reacts only with steam. When steam is passed over red-hot iron, iron (II,III) oxide and hydrogen gas are formed. 

 

 

 

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Which of the following solid salt on heating with K2Cr2O7 and Conc. H2SO4 orange,red vapours are evolved which turn aquous NaOH solution yellow?

(a) NaBr

(b)NaCl

(c) NaNO3

(d) NaI

(b) NaCl(s) + K2Cr2O7 + H2SO4 (few drops)reactionNon redoxCrO2Cl2+H2O

CrO2Cl2 + OH-(aq.)CrO4(aq)2-+Cl-+2H2O

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Consider the following transformation:

2CuX2room temperature2CuX+X2

Then X- can be :

(a) F-,Br-

(b) Cl-,Br-

(c) CN-

(d) Cl-,F-

(c) Cu(CN)2 and CuI2 being unstable spontaneously decomposes into CuCN and CuI respectively at room temperature

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Fe is made passive by :

(a) dil . H2SO4

(b) dil. HCl

(c) Conc. HNO3

(d) Conc. H2SO4

(b) Chloroplatinic acid is H2[PtCl6],which is dibasic

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The iron salt used in blue prints is:

(a) FeC2O4

(b) Fe2(C2O4)3

(c) K4Fe(CN)6

(d) FeSO4

(a) 2CrO42-+2H+Cr2O72- +H2O

Cr2O72-+2OH-2CrO42-+H2O

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Which has highest melting point?

1. Cr

2. Fe

3. Cu

4. Mo

(1) Greater than number of unpaired electrons, more is the covalency and higher is the melting point

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The colour of KMnO4 is due to

1. d-d transition

2. Charge transfer spectra

3. Polarisation of ion

4. p-d transition

(2) In KMnO4, Mn has no d-electron and colour is due to charge transfer spectra

Difficulty Level:

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Which of the following element does not show the variable oxidation state?

1. Fe

2. Mn

3. Cu

4. Zn

(4) Pseudo transition element have 10 electro in d subshell , so cannot lose electron from d subshell.

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