S1.4 Counting particles by mass: The mole

Question 1

the mole (mol)

Answer 1

• the SI unit of amount of substance
• 1 mole contains exactly the number of elementary entities (atom, molecule, ion, electron, particle, specified group of particles) given by the Avogadro constant

Question 2

Avogadro constant (Na)

Answer 2

6.02 x 10^23

Question 3

relative atomic mass of an element

Answer 3

the weighted average of the masses of the isotopes relative to 1/12 of the mass of a C-12 atom

Question 4

equation for number of moles

Answer 4

n = m/M

Question 5

empirical formula of a compound

Answer 5

• gives the simplest ratio of atoms of each element present in that compound
• percentage comparison by mass of elements in a compound
• ionic compound formula = always empirical

Question 6

molecular formula of a compound

Answer 6

• gives the actual number of atoms of each element present in a molecule

Question 7

molar concentration

Answer 7

• determined by the amount of solute and the volume of solution
• n = CV
• g dm^-3
• mol dm^-3

Question 8

Avogadro’s law

Answer 8

• states that equal volumes of gases measured under the same conditions of temperature and pressure have equal numbers of molecules
• only applies to ideal gases