stoichiometry

Question 1

Define relative isotopic mass

Answer 1

mass of one atom of an isotope of an element / (1/12 x the mass of 12C atom)

Question 2

Define relative atomic mass

Answer 2

average mass of one atom of an element / (1/12 x the mass of one 12C atom)

Question 3

What is relative molecular mass?

Answer 3

average mass of one molecule of a substance / (1/12 the mass of one 12C atom) FOR COVALENT COMPOUNDS

Question 4

What is relative formula mass?

Answer 4

average mass of one formula unit of a substance / (1/12 the mass of one 12C atom) FOR IONIC COMPOUNDS

Question 5

Define empirical formula.

Answer 5

The empirical formula of a compound is the simplest formula which shows the ratio of the atoms of the different elements in the compound.

Question 6

What is molecular formula?

Answer 6

The molecular formula of a compound is the formula which shows the actual number of atoms of each element in one molecule of the compound.

Question 7

Explain the Arrhenius Theory of acids and based, as well as its limitations.

Answer 7

An acid is a substance that dissociates in water to produce H3O+ (aq) ions, known as hydronium or hydroxonium ions.
A base is a substance that dissociates in water to produce OH- (aq).
When an acid is added to a base, the H+ ion reacts with the OH- ion to produce a molecule of water and undergoes neutralisation.
The limitation of this model is that it is restricted to aqueous solutions only.

Question 8

Explain the Bronsted-Lowry Theory of acids and bases, as well as its limitations.

Answer 8

An acid is defined as any species which donates a proton, H+. (An acid must contain a H in its formula.)
A base is defined as any species which accepts a proton, H+. (A base must contain a lone pair of electrons to bind the H+ ion.)
A Bronsted-Lowry acid-base reaction involves the transfer of a proton from an acid to a base.
However, this still could not explain why substances such as BF3 or AlCO3 do not contain any hydrogen atom but are yet known to behave as acids.