Question
Metal M has only one oxidation number and forms a compound with the formula \({\text{MC}}{{\text{O}}_{\text{3}}}\). Which formula is correct?
A. \({\text{MN}}{{\text{O}}_{\text{3}}}\)
B. \({\text{MN}}{{\text{H}}_{\text{4}}}\)
C. \({\text{MS}}{{\text{O}}_{\text{4}}}\)
D. \({\text{MP}}{{\text{O}}_{\text{4}}}\)
▶️Answer/Explanation
C
Since M forms \({\text{MC}}{{\text{O}}_{\text{3}}}\) it has +2 oxidation state which is its only oxidation state.
It will form \({\text{MS}}{{\text{O}}_{\text{4}}}\) with a sulfate ion.
Question
Which species is oxidized in the following reaction?
\[{\text{2A}}{{\text{g}}^ + }{\text{(aq)}} + {\text{Cu(s)}} \to {\text{2Ag(s)}} + {\text{C}}{{\text{u}}^{2 + }}{\text{(aq)}}\]
A. \({\text{A}}{{\text{g}}^ + }\)
B. Cu
C. Ag
D. \({\text{C}}{{\text{u}}^{2 + }}\)
▶️Answer/Explanation
B
As Cu undergoes increase in its oxidation state from 0 in Cu(s) to +2 in Cu2+(aq), hence Cu oxidizes in this reaction.
Question
Which list represents the halogens in increasing order of oxidizing strength (weakest oxidizing agent first)?
A. \({\text{C}}{{\text{l}}_{\text{2}}}\quad {{\text{I}}_{\text{2}}}\quad {\text{B}}{{\text{r}}_{\text{2}}}\)
B. \({{\text{I}}_{\text{2}}}\quad {\text{B}}{{\text{r}}_{\text{2}}}\quad {\text{C}}{{\text{l}}_{\text{2}}}\)
C. \({{\text{I}}_{\text{2}}}\quad {\text{C}}{{\text{l}}_{\text{2}}}\quad {\text{B}}{{\text{r}}_{\text{2}}}\)
D. \({\text{C}}{{\text{l}}_{\text{2}}}\quad {\text{B}}{{\text{r}}_{\text{2}}}\quad {{\text{I}}_{\text{2}}}\)
▶️Answer/Explanation
B
Oxidizing power is in the order: I2<Br2<Cl2<F2 based on electrochemical series.
Question
Which are redox reactions?
I. \({\text{2FeC}}{{\text{l}}_2} + {\text{C}}{{\text{l}}_2} \to 2{\text{FeC}}{{\text{l}}_{\text{3}}}\)
II. \({\text{Mg}} + {\text{2HN}}{{\text{O}}_3} \to {\text{Mg(N}}{{\text{O}}_3}{)_2} + {{\text{H}}_2}\)
III. \({{\text{H}}_2}{\text{O}} + {\text{S}}{{\text{O}}_3} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_4}\)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
A
In reaction I, Fe undergoes oxidation from +2 in FeCl2 to +3 FeCl3. Cl undergoes reduction from 0 in Cl2 to -1 in FeCl3. Hence it is a redox reaction.
In reaction II, Mg undergoes oxidation from 0 in Mg to +2 in Mg(NO3)2 and H undergoes reduction from +1 in HNO3 to 0 in H2.Hence it is a redox reaction.
In reaction III, H, O and S remain in their same oxidation states of +1, -2 and +6 respectively. It is not a redox reaction.
Question
In which species does sulfur have an oxidation number of 0?
A. \({\text{S}}{{\text{O}}_{\text{3}}}\)
B. \({{\text{S}}_{\text{8}}}\)
C. \({\text{N}}{{\text{a}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\)
D. \({{\text{H}}_{\text{2}}}{\text{S}}\)
▶️Answer/Explanation
B
The oxidation state of S in S8 is zero. Sulphur exists in elemental form so it has 0 oxidation number.
Question
Which of the following does not react with dilute HCl(aq)?
A. Na2CO3
B. Cu
C. Zn
D. CuO
▶️Answer/Explanation
B
Cu lies below H in the reactivity series hence it does not react with HCl.
Zn lies above H, it can react with HCl.
Sodium carbonate is a base that reacts with an acid, i.e., hydrochloric acid to give Sodium chloride salt along with carbon dioxide and water.
Hydrochloric acid is a strong acid. -Metal oxides are usually basic in nature. Copper oxide is basic, so it reacts with hydrochloric acid to form copper chloride and water.