4.1-4.3 Symbols, equations and Formulae

H2

________ has two hydrogen atoms, while HCl contains one hydrogen atom and one chlorine atom.

Group IV

Carbon, for example, belongs to ________, which means that a single carbon atom can form four single bonds or two double bonds.

concept of valency

The ________ is utilized to deduce compound formulas.

A compound contains 3 carbon atoms and 8 hydrogen atoms. Write the chemical formula of this compound

C3H8

What is the chemical formula of sodium oxide, formed from Na+ and O2- ions?

Na2O
Charges must balance so 2 sodium ions are required.

What are the state symbols used in chemical equations?

(g) - gas
(aq) - aqueous (l) - liquid
(s) - solid

What is an ionic equation?

Ionic equations only show the reacting ions and can be written for any reaction involving ions in solution.

What does the term relative formula mass mean?

The sum of the relative atomic masses of atoms in a formula unit. Used for giant ionic structures.

Define the mole

The amount of any substance containing the same number of particles as there are atoms in exactly 12 g of carbon-12 (6.02 x 1023 particles).

Define the Avogadro constant (extended only)

The number of particles in one mole of a
substance. This is 6.02 x 1023 particles

What is the equation that relates moles with the Avogadro constant?

Number of particles/atoms/ions = moles x Avogadro’s constant

What is the molar volume of gas at room temperature and pressure?

24 dm3

What is RTP? (extended only)

Room temperature and pressure:

• 20oC

• 1 atmosphere

What equation links molar volume at RTP and moles?

Volume of gas at RTP (dm3) = moles x 24