431.

Most common oxidation states shown by cerium are

• +2, +4

• +3, +4

• +3, +5

• +2, +3

Which gives + 7 oxidation state ?

• Mn(25)

• Cr (24)

• Cu(29)

• Fe(26)

Which of the following transitions involves maximum amount of energy?

• ${{\mathrm{M}}^{-}}_{\left(\mathrm{g}\right)\hspace{0.17em}}\to {\mathrm{M}}_{\left(\mathrm{g}\right)}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{+}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)}^{+} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{2+}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)}^{2+} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{3+}$

Select the coloured compound amongst the following .

(At. no. Ti= 22, Cr= 24, Cu= 29, Zn= 30)

• TiCl₄

• CrCl₃

• ZnCl₃

• CuCl

The only radioactive element among the lanthanoids is

• gadolinium

• holmium

• promethium

• neodymium

Identify a 'chemical twin' among the following.

• Zr-Ta

• Nb-Tc

• Hf-Re

• Nb-Ta

What is the general molecular formula of the product obtained on heating lanthaniods (Ln) with sulphur?

• LnS

• LnS₃

• Ln₃S₂

• Ln₂S₃

Choose the correct matching of transition metal ion and magnetic moment from the codes given below. (Atomic number: Ti = 22, V =23, Fe= 26)

Transition element	Magnetic moment (BM)
A. Titanium (III)	i. 4.9
B. Vanadium (II)	ii. 1.73
C. Iron (II)	iii. 3.87

• A - ii; B - iii; C - i

• A - ii; B - i; C - iii

• A - i; B - ii; C - iii

• A - i; B - iii; C - ii

The hardest lanthanide element is

• Sm

• La

• Gd

• Dy

How is sodium chromate converted into sodium dichromate in the manufacture of potassium dichromate from chromite ore?

• By the action of concentrated sulphuric acid

• By roasting with soda ash

• By the action of sodium hydroxide

• By the action of limestone