Atoms and Molecules – MCQ Questions with Answers for CBSE 9th class
1-The smallest particles beyond which further division will not be possible.
(A) Atom
(B) Molecule
(C) Compound
(D) All of the above
2-Law of conservation of mass states that mass can neither be created nor destroyed in a ___ .
(A) atomic structure
(B) chemical reaction
(C) open vessel
(D) all of the above
3-As per Law of constant proportions, In a compound such as water, the ratio of the mass of hydrogen to the mass of oxygen is always ___ .
(A) 1:2
(B) 1:4
(C) 1:8
(D) 1:16
4- As per Law of constant proportions, in ammonia, nitrogen and hydrogen are always present in the ratio ___ by mass.
(A) 8:3
(B) 10:3
(C) 12:3
(D) 14:3
5- Atoms of a given element are identical in
(A) mass
(B) chemical properties
(C) mass as well as chemical properties
(D) none of the above
6-Relative size of atomic radius of atom of hydrogen is
(A) 10-4 m
(B) 10-6 m
(C) 10-8 m
(D) 10-10 m
7-The first scientist to use the symbols for elements in a very specific sense, is
(A) John Dalton
(B) Joseph L. Proust
(C) Lavoisier
(D) None of the above
8-The relative atomic masses of all elements have been found with respect to an atom of ___ .
(A) Hydrohen-1
(B) carbon-12
(C) Nitrogen-14
(D) Oxygen-16
9-A (an) ___ is in general a group of two or more atoms that are chemically bonded together.
(A) element
(B) molecule
(C) compound
(D) none of the above
10-The number of atoms constituting a (an) ___ is known as its atomicity.
(A) element
(B) molecule
(C) compound
(D) none of the above
11-Following elements are diatomic
(A) Oxygen
(B) Hydrogen
(C) Nitrogen
(D) All of the above
12-In Carbon dioxide, carbon and oxygen are always present in the ratio ___ by mass.
(A) 1:8
(B) 14:3
(C) 12:3
(D) 3:8
13-The chemical formula of a compound is a symbolic representation of its
(A) structure
(B) composition
(C) properties
(D) all of the above
14-The combining power (or capacity) of an element is known as its
(A) atomicity
(B) valency
(C) charge
(D) none of the above
15-The relative mass of a molecule is expressed in
(A) atomic mass unit
(B) formula mass unit
(C) both (A) and (B)
(D) none of the above
16-The mass of 1 mole of a substance is equal to its ___ in grams.
(A) relative atomic mass
(B) molecular mass
(C) relative atomic or molecular mass
(D) none of the above
17-1 mole (of anything) = ___ in number
(A) 6.022 × 1020
(B) 6.022 × 1021
(C) 6.022 × 1022
(D) 6.022 × 1023
ANSWERS:
1-(A), 2-(B), 3-(C), 4-(D), 5-(C), 6-(D), 7-(A), 8-(B), 9-(B), 10-(B), 11-(D), 12-(D), 13-(B), 14-(B), 15-(A), 16-(C), 17-(D)