Question
What is the overall charge, x, of the chromium (III) complex?
![[Cr(H_2O)_4Cl_2]^x](https://www.iitianacademy.com/wp-content/uploads/2022/01/img_61dbd81fa57f4.gif)
A 0
B 1+
C 2–
D 3+
▶️Answer/Explanation
Ans: B
Cr has +3 charge. H2O zero and Cl -1.
Overall charge of complex = +3-2(1)=+1.
Question
In which complexes does iron have an oxidation number of \( + 3\)?
I. \({{\text{[Fe(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_6}{\text{]}}^{3 + }}\)
II. \({{\text{[Fe(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_5}{\text{(CN)]}}^{2 + }}\)
III. \({{\text{[Fe(CN}}{{\text{)}}_6}{\text{]}}^{3 – }}\)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
D
In I, Fe + 6(0) = +3 , Fe = +3.
In II, Fe + 5(0) -1 = +2 , Fe = +3.
In III, Fe +6(-1) = -3, Fe = +3.
Question
Which solutions have a pH less than 7?
I. \({\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3}({\text{aq)}}\)
II. \({\text{[Fe(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_6}{\text{]C}}{{\text{l}}_3}{\text{(aq)}}\)
III. \({{\text{(N}}{{\text{H}}_4}{\text{)}}_2}{\text{S}}{{\text{O}}_4}{\text{(aq)}}\)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
C
Sodium carbonate is a basic salt as it is formed when a strong base (sodium hydroxide) is partially neutralized by a weak acid (carbonic acid). It has pH greater than 7.
The reaction between the sulphuric acid and the ammonium hydroxide produces ammonium sulfate. Sulphuric acid is a strong acid and ammonium hydroxide is a weak base. Therefore, the salt formed by ammonium sulphate is acidic. Hence, it has pH less than 7.
Solutions containing 3+ hexa aqua ions tend to have pH’s in the range from 1 to 3.
Question
Which metal nitrate solution is coloured?
A. \({\text{Zn(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}{\text{(aq)}}\)
B. \({\text{Ni(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}{\text{(aq)}}\)
C. \({\text{Mg(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}{\text{(aq)}}\)
D. \({\text{Sc(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{3}}}{\text{(aq)}}\)
▶️Answer/Explanation
B
is colored because nickel (II) ion, , absorbs visible light in the blue-green region of the spectrum. The absorption of light causes electrons in the ion to jump from a lower energy level to a higher energy level within the d-orbitals. This absorption of light leads to the complementary color being observed. Therefore, appears coloured in aqueous solution.
Question
What is the electron configuration of \({\text{S}}{{\text{n}}^{2 + }}\)?
A. \(1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^6}4{{\text{s}}^2}3{{\text{d}}^{10}}4{{\text{p}}^6}5{{\text{s}}^2}4{{\text{d}}^{10}}5{{\text{p}}^2}\)
B. \(1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^6}4{{\text{s}}^2}3{{\text{d}}^{10}}4{{\text{p}}^6}5{{\text{s}}^2}4{{\text{d}}^{10}}\)
C. \(1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^6}4{{\text{s}}^2}3{{\text{d}}^{10}}4{{\text{p}}^6}4{{\text{d}}^{10}}5{{\text{p}}^2}\)
D. \(1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^2}3{{\text{p}}^6}4{{\text{s}}^2}3{{\text{d}}^{10}}4{{\text{p}}^6}5{{\text{s}}^2}4{{\text{d}}^8}5{{\text{p}}^2}\)
▶️Answer/Explanation
B
Sn: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p2.
The tin atom donates two electrons in the 5p orbital to form a tin ion(Sn2+).
Here, the electron configuration of tin ion(Sn2+) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2.