Chemical Reactivity: MCQs and Answers with explanation

1. Which one of the following is the most basic?

a) MgO
b) BaO
c) CaO
d) SrO

... Answer is b)
Explanation: Basic character of oxides of metals increases with increase in electropositive character (ability to loose the electron). Down the group, electropositive character of metal increases as atomic size or atomic radius increaeses due to increase in shells and decrease in effective nuclear charge due to increase in sheilding effect.
As Ba is at bottom of these elements, therefore, Ba can loose valence electron easily and hence shows the most electropositive character. So, BaO is the most basic .

2. Which of the following oxides is amphoteric oxide?

a) Na₂O
b) Al₂O₃
c) MgO
d) SO₂

... Answer is b)
Explanation: Amphoteric oxides are compounds which have ability to react as acid and base. Al₂O₃ can act as an acid and base depending upon the conditions. Therefore, Al₂O₃ is amphoteric. Oxide of Al show amphoteric behavious as it is present on boundry where basic oxides of element start to become acidic oxides of elements.

3. Which of the following elements is the most metallic?

a) Al
b) Na
c) Mg
d) Li

... Answer is b)
Explanation: Metallic character is related to ability of an element to loose the electron or to show the reactivity. Down the group, ability of metal to loose electron increases as atomic size or atomic radius increaeses due to increase in shell and decrease in effective nuclear charge due to increase in sheilding effect. From left to right in the period, atomic size or atomic radius decrease and effective nuclear charge increase, so ability to loose the electron decreases.
As Na is present at lower and left of these elements in periodic table, so, it can loose valence electron easily and hence shows the most metallic character.

4. Valence shell electronic configuration of alkaline earth metal is

a) ns¹
b) ns² ​​​​​​, np¹
c) ns²
d) ns² ​​​​​​, np⁶

... Answer is c)
Explanation: Valence shell electronic configuration of alkaline earth metal is ns².

5. Which of the following metals is not Noble metal?

a) Au
b) Cu
c) Hg
d) Ag

... Answer is c)
Explanation: Noble metals are the metals which are difficult to be oxidized by acids or bases even at high temperature and pressure. These metals are silver, gold and copper.

6. Which of the following elements is the least non metallic?

a) Si
b) S
c) P
d) Cl

... Answer is Si)
Explanation: Metallic character decreases from left to right in the period while non-metallic character decreases from right to left in the period. These elements are present in third period and among these Si is the leaset non-metallic as it iis present on the left of these elements while Cl is the most non-metallic as it is present on right side of these elements in the period.

7. Oxidising power of--------- is the highest?

a) I₂
b) Br₂
c) Cl₂
d) F₂

... Answer is d)
Explanation: Oxidizing power of an element generally depends upon electronegitivity of an element. As F₂ is the most electronegative due to small atomic size, so oxidizing power of F₂ is the highest.

8. Chlorine cannot oxidise the-----ion

a) Iodide
b) Fluoride
c) Bromide
d) Astatide

... Answer is b)
Explanation: Chlorine cannot oxidize the fluoride ion due to relative lower electronegativity of chlorine. Chlorine can only oxidize the bromide and iodide which have relative lower oxidizing powers.

9. Sodium is more reactive than Lithium but less reactive than?

a) Mg
b) Al
c) Rb
d) All of these

... Answer is c)
Explanation: Reactivity of metals depend upon the their electropositive character. Sodium is more reactive than Mg and Al due to its relative more electropositive character, but less reactive than Rb due to its relative less electropositive character.

10. Which of the following is the strongest acid?

a) HI
b) HCl
c) HF
d) HBr

... Answer is a)
Explanation: HI is the srongest acid because of weakest H-I bond while H-F is weakest acid because of weakest H-F bond.