Elements that generally exhibit multiple oxidation states and whose ions in an aqueous medium are usually colored are:

1. Metalloids

2. Transition elements

3. Non-metals

4. Noble 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

At pH = X, \(\text{CrO}_4^{2-}\)​ (yellow) changes to \(\text{Cr}_2\text{O}_7^{2-}\) (orange), and vice versa at pH = Y.
What are the values of X and Y, respectively?

1. 6, and 8

2. 6, and 5

3. 8, and 6

4. 7, and 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

The low melting point of manganese in the 1st transition series is due to:

1. strong metallic bond due to d¹⁰ configuration

2. weak metallic bond due to d⁵ configuration

3. weak metallic bond due to d⁷ configuration

4. none of the above

Which element among the following 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