Lanthanoid contraction is caused due to :

1. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge

2. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge

3. the same effective nuclear charge from Ce to Lu

4. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge

Elements which generally exhibit multiple oxidation states and whose ions in aqueous medium are usually coloured :

1. metalloids

2. transition elements

3. non-metals

4. gases

CuSO_4 (aq.)$\stackrel{{\mathrm{H}}_2\mathrm{S}\uparrow }{\to }$M$\downarrow$$\underset{\mathrm{of} \mathrm{KCN}}{\overset{\mathrm{Excess}}{\to }}$N+O

Then final products N and O are respectively.

1. [Cu(CN)₄]^3-,(CN)₂

2. CuCn,(CN)₂

3. [Cu(CN)₄]^2-,(CN)₂

4. Cu(CN)₂,K₂S

CrO₄^2- (yellow) changes to Cr₂O₇^2- (orange) in pH =x and vice versa in pH=y. Hence, x and y are:

1. 6,8

2. 6,5

3. 8,6

4. 7,7

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

1. Fe₂O₃ +H₂

2. Fe₃O₄ +H₂

3. FeO +H₂

4. FeO+ H₂ +O₂

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

1. NaBr

2. NaCl

3. NaNO₃

4. NaI

Fe is made passive by :

1. dil . H₂SO₄

2. dil. HCl

3. Conc. HNO₃

4. Conc. H₂SO₄

The iron salt used in blue prints is:

1. FeC₂O₄

2. Fe₂(C₂O₄)₃

3. K₄Fe(CN)₆

4. FeSO₄

Which has the highest melting point?

1. Cr

2. Fe

3. Cu

4. Mo

The colour of KMnO₄ is due to

1. d-d transition

2. Charge transfer spectra

3. Polarisation of ion

4. p-d transition