set 1 MCQ Questions & Answers Detailed Explanation

Question : 1

Which fact is not valid for Dobereiner's triads?

a) The properties of middle element is roughly average of the other two elements

b) The elements of triads belong to the same group of modern periodic table

c) The atomic weight of middle element is roughly average of the other two elements

d) The elements of triads have same valency electrons.

Question : 2

Assertion (A):
A chemical reaction becomes faster at a higher temperature.
Reason (R):
At higher temperature, molecular motion becomes more rapid.

a) Both (A) and (R) are true, but (R) is not the correct explanation of (A)

b) (A) is true, but (R) is false

c) Both (A) and (R) are true and (R) is the correct explanation of (A)

d) (A) is false, but (R) is true

Question : 3

On moving horizontally across a period, the number of electrons in the outermost shell increases from ...... to .......

a) 2, 18

b) 1, 8

c) 2, 8

d) 1, 18

Question : 4

Change of water into the vapour is called

a) Physical

b) Chemical

c) Natural

d) Biological

Question : 5

The elements with atomic numbers 2, 10, 18, 36, 54 and 86 are all

a) noble gases

b) noble metals

c) halogen

d) light metals