Atoms and Molecules

Which statement about atoms and molecules is correct?

1. Atoms always exist independently.
2. Molecules are formed when atoms combine chemically.
3. Molecules are smaller than atoms.
4. Atoms can be seen with the naked eye.

The formula of calcium carbonate is

1. CaCO2
2. CaCO3
3. Ca2CO3
4. Ca(CO3)2

Which of the following is a polyatomic ion?

1. Na+
2. Cl-
3. SO4(2-)
4. H+

The chemical symbol for sodium is

1. So
2. Na
3. S
4. N

Which formula represents carbon dioxide?

1. CO
2. CO2
3. C2O
4. C2O2

The atomicity of nitrogen gas (N2) is

1. 1
2. 2
3. 3
4. 4

Avogadro's number is

1. 6.022 x 10^22
2. 6.022 x 10^23
3. 3.011 x 10^23
4. 9.8 x 10^23

The SI unit of the amount of substance is

1. Gram
2. Kilogram
3. Mole
4. Litre

The molecular formula of oxygen gas is

1. O
2. O2
3. O3
4. O4

The chemical formula of water is

1. HO
2. H2O
3. H2O2
4. OH

The Law of Constant Proportions states that

1. Elements combine in varying proportions.
2. A compound always contains the same elements in the same fixed proportion by mass.
3. Mass increases during a reaction.
4. Atoms can be destroyed.

Which law states that mass can neither be created nor destroyed during a chemical reaction?

1. Law of Multiple Proportions
2. Law of Conservation of Mass
3. Avogadro's Law
4. Boyle's Law

A molecule is

1. A charged particle
2. The smallest particle of a substance capable of independent existence
3. A mixture of two elements
4. A single proton

The smallest particle of an element that retains its chemical properties is called

1. Molecule
2. Atom
3. Ion
4. Compound

Who proposed the atomic theory that explains the nature of matter?

1. Isaac Newton
2. John Dalton
3. Albert Einstein
4. Ernest Rutherford