A pair among the following that has both coloured ions in the aqueous solution is-
(At. no : Sc =21, Ti = 22, Ni = 28, Cu = 29, Co = 27)

1.	Ni2+, Ti3+	2.	Sc3+, Ti3+
3.	Sc3+, Co2+	4.	Ni2+, Cu+

Which of the following is called Wilkinson's catalyst?

(1) $\left[\mathrm{RhCl}\right({\mathrm{PPh}}_3{)}_3]$             (2) ${\mathrm{TiCl}}_4+({\mathrm{C}}_2{\mathrm{H}}_5{)}_3\mathrm{Al}$

(3) $({\mathrm{C}}_2{\mathrm{H}}_5{)}_4\mathrm{Pb}$                  (4) $\left[{\mathrm{PtCl}}_2\right({\mathrm{NH}}_3{)}_2]$

Which of the following solid salt on heating with solid ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ and  conc.${\mathrm{H}}_2{\mathrm{SO}}_4$ orange red vapours are evolved which turn aqueous NaOH solution yellow?

(a)NaBr               (b) NaCl

(c) ${\mathrm{NaNO}}_3$           (d) NaI

Which of the following is true for the species $3{\mathrm{d}}^4$ configuration ?

(A) ${\mathrm{Cr}}^{2+}$ is reducing in nature                               

(B) ${\mathrm{Mn}}^{3+}$ is oxidising in nature.

(C) Both (A) and (B)                                             

(D) None of these

In which compound does vanadium have an oxidation number of +4?

(1) ${\mathrm{NH}}_4{\mathrm{VO}}_2$                                 

(2) ${\mathrm{K}}_4\left[\mathrm{V}{\left(\mathrm{CN}\right)}_6\right]$

(3) ${\mathrm{VSO}}_4$                                     

(4) ${\mathrm{VOSO}}_4$

 The increasing order of oxidising power among the following species is:

1. ${{}_{}}^{}$\(\mathrm{VO}_2^{+}<\mathrm{Cr}_2 \mathrm{O}_7^{2-}<\mathrm{MnO}_4^{-}\)   
2. \(\mathrm{VO}_2^{+}<\mathrm{MnO}_4^{-}<\mathrm{Cr}_2 \mathrm{O}_7^{2-}\)  
3. \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}<\mathrm{VO}_2^{+}<\mathrm{MnO}_4^{-}\)
4. \(\mathrm{Cr}_2 \mathrm{O}_7{ }^{2-}<\mathrm{MnO}_4^{-}<\mathrm{VO}_2^{+}\)

Select the correct statement :

(A) ${\mathrm{PH}}_3$ reduces ${\mathrm{AgNO}}_3$ to metallic Ag.

(B) Organic tissues turn ${\mathrm{AgNO}}_3$ black by reducing it to Ag.

(C) $\mathrm{AgCN}$is soluble in $\mathrm{KCN}$.

(D) All are correct statements.

Which one of the following statements is not correct

(1) Nickel forms Ni(CO)₄

(2) All the transition metals form mono metallic carbonyls

(3) Carbonyl are formed by transition metals

(4) Transition metals form complexes

Which of the following pairs of compounds are more stable

(A) $K_2\left[NiC{l}_6\right],\left[Pt\right(CN{)}_4{]}^{2-}$

(B) NiCl₄, PtCl₄

(C) $\left[Ni\right(CN{)}_4{]}^{2-}, K_2\left[Pt\right(C{l}_6\left)\right]$

(D) PtCl₂, NiCl₂

Which of the following ions has the most unpaired electrons?