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Chemistry — ATOMS AND MOLECULES

50 Questions Class 9 MCQs
1
Who gave the law of conservation of mass?
2
The law of definite proportions was given by:
3
Who proposed the atomic theory?
4
According to Dalton’s atomic theory, atoms of different elements:
5
Which of the following is a triatomic molecule?
6
The smallest particle of an element that can take part in a chemical reaction is called:
7
The symbol of sodium is derived from its Latin name:
8
The formula of water is:
9
The molecular mass of \(\mathrm{CO_2}\) is:
10
Which of the following is a polyatomic ion?
11
The atomic mass unit (amu) is based on:
12
The chemical formula of calcium hydroxide is:
13
Who gave the law of multiple proportions?
14
The number of atoms in one molecule of ammonia \(\mathrm{(NH_3)}\) is:
15
The valency of oxygen is:
16
The chemical formula of sulphuric acid is:
17
Avogadro’s number represents:
18
The molecular formula of glucose is:
19
The ratio of hydrogen to oxygen in water by mass is:
20
The total number of atoms in one molecule of \(\mathrm{CO_2}\) is:
21
The formula of magnesium chloride is:
22
Which of the following is a diatomic molecule?
23
One mole of any substance contains:
24
The molecular mass of \(\mathrm{H_2SO_4}\) is:
25
Which law states that mass can neither be created nor destroyed?
26
The combining capacity of an element is called its:
27
The formula of aluminium oxide is:
28
The relative atomic mass of an element is the ratio of the average mass of one atom to:
29
The molecular formula of methane is:
30
The symbol 'S' represents:
31
Which of the following is a compound?
32
The chemical formula of carbon dioxide is:
33
Which of the following correctly represents a molecule of an element?
34
The atomicity of phosphorus \(\mathrm{(P_4)}\) is:
35
The mass of one mole of water is:
36
The molecular formula of hydrogen peroxide is:
37
The term ‘molecule’ is best defined as:
38
The total number of atoms in one molecule of glucose \(\mathrm{(C_6H_12O_6)}\) is:
39
The atomic mass of oxygen is:
40
The number of moles in 18 g of water is:
41
Which of the following statements is correct according to Dalton’s theory?
42
The formula of ammonium sulphate is:
43
The molecular formula of sulphur dioxide is:
44
The number of atoms in one mole of oxygen gas \(\mathrm{(O_2)}\) is:
45
Which of the following is not a correct chemical formula?
46
Which of the following is a cation?
47
The number of hydrogen atoms in 1 molecule of \(\mathrm{C_2H_6}\) is:
48
The valency of aluminium is:
49
The molecular mass of calcium carbonate \(\mathrm{(CaCO_3)}\) is:
50
Which of the following pairs of elements form a compound in a 1:1 ratio?

Frequently Asked Questions

An atom is the smallest particle of an element that retains its chemical properties.

A molecule is a group of two or more atoms chemically bonded together.

Dalton’s theory states matter is made of indivisible atoms, identical for each element, combining in fixed ratios.

A chemical formula represents a compound using symbols and shows elements’ proportions.

Atomic mass unit is a standard mass unit equal to 1/12 the mass of one carbon-12 atom.

Atomicity is the number of atoms in a molecule of an element or compound.

A mole is the amount of substance containing Avogadro’s number of particles (6.022 × 10²³).

Mass is neither created nor destroyed during a chemical reaction.

Elements combine in a fixed mass ratio to form a compound.

It is the ratio of the average atomic mass of an element to 1/12 of a carbon-12 atom’s mass.

Avogadro’s number is 6.022 × 10²³, the number of particles in one mole of substance.

An ion is an atom or molecule with a net electric charge due to electron gain or loss.

Atom is a single particle; molecule consists of two or more atoms bonded together.

The symbol for sodium is Na.

Polyatomic ions are ions formed by a group of atoms with an overall charge.

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