Unit 1, Topic 1: Formulae, Equations and Amount of Substance

Question 1

1.1 Define “atom”

Answer 1

the smallest particle that cannot be broken down into anything simpler by chemical means

Question 2

1.1 Define “molecule”

Answer 2

two or more atoms chemically bonded together

Question 3

1.1 Define “ion”

Answer 3

atoms that lose or gain electrons

Question 4

1.1 Define “compound”

Answer 4

a substance containing more than one type of element chemically joined together

Question 5

1.1 Define “empirical formula”

Answer 5

the simplest form of the molecular formula

Question 6

1.1 Define “molecular formula”

Answer 6

only shows the number of each type of atom in the molecule but not its structure

Question 7

1.2 Define “mole”

Answer 7

a unit for the amount of substance

Question 8

1.2 Define “mole” in terms of mass

Answer 8

amount of substance that has a mass equal to the relative atomic mass or relative molecular mass

Question 9

1.4 Define “relative atomic mass”

Answer 9

the average mass of an atom when compared to 1/12 of the mass of carbon-12 atoms.

Question 10

1.4 Define “relative molecular mass”

Answer 10

the mass of a molecule of both elements and compound when compared to 1/12 of the mass of carbon-12 atom.

This term is only applied to COVALENT MOLECULES.

Question 11

1.4 Define “relative formula mass”

Answer 11

the mass of compound used for ionic compound, ion and giant structure.

This term applies to IONIC BONDS only

Question 12

1.4 Define “Molar mass”

Answer 12

the mass of one mole of any substance (unit = g/mol)

Question 13

1.2 What is the formula for moles in terms of mass?

Answer 13

Mole = mass of substance/Molar mass

Question 14

1.2 Define “mole” in terms of particles

Answer 14

the amount of substance that contains 6.02 x 10^23 particles (Avogadro’s constant)

Question 15

1.2 What is the formula for moles in terms of particles?

Answer 15

Mole = number of particles/Avogadro’s constant

Question 16

1.4 What is the unit for atom, covalent bonds and ionic bonds?

Answer 16

atoms, molecules and formula unit respectively

Question 17

1.2 Define “mole” in terms of volume of gas

Answer 17

the amount of substance that has volume equal to 24dm^3 measured at room temperature (25C) and pressure (1.01x10^25 Pa)

Question 18

1.8 Define “Molar volume”

Answer 18

the volume of gas in one mole measured at RTP

Question 19

1.8 Define “the ideal gas equation”

Answer 19

an equation used to calculate involved gas substances at another temperature other than room temperature

Question 20

1.8 What is the ideal gas equation”

Answer 20

PV = nRT

P = pressure in Pa
V = volume in m^3
n = mole of gas
R = gas constant (8.31 J/K/mol)
T = temp in K (C+273)