6. The Mole Concept and Stoichiometry

Question 1

Define relative atomic mass.

Answer 1

Relative atomic mass is the ratio of average mass of atom of an element 1/12 of the mass of 12C atom.

Question 2

Define relative isotopic mass.

Answer 2

Relative isotopic mass is the ratio of the mass of an atom of isotope to 1/12 of the mass of a 12C atom.

Question 3

Define relative molecular mass.

Answer 3

Relative molecular mass is the ratio of the average mass of a molecule to 1/12 of the mass of a 12C atom

Question 4

Define relative formula mass.

Answer 4

Relative formula mass is the ratio of the average mass of a formula unit of an ionic compound to 1/12 of the mass of a 12C atom.

Question 5

Define mole in terms of Avogadro constant.

Answer 5

One mole of any substance is the amount of substance which contains the same number of particles as there are atoms in 12.0g of the 12C isotopes (i.e. 1 mole of particles contains 6.02 x 10^23 particles).

The Avogadro constant, L, is the number of C atoms present in 12.0g of 12C atoms.

Question 6

Define the terms empirical and molecular formula.

Answer 6

Empirical formula is the formula that shows the simplest whole number ratio of the number of atoms of each element present in the substance.

Molecular formula is the formula that shows the actual number of atoms of each element in one molecule of the compound.