Chemistry 2A/2B
1
Coghlan
Assignment 3
Due _______________
1.
In general, what conditions cause two atoms to combine to form a bond that is mainly
covalent?
2.
The Group I and II metals are not found free (unreacted) in nature. Why is this?
3.
Why do atoms and ions of the same element have almost the same mass?
4.
Within the Group 1 elements, rubidium has a lower first ionisation energy than sodium.
Explain why.
5.
Write the correct chemical formula for each of the following;
(a) hydride ion
(b) bicarbonate ion
(c) bromine liquid
(d) sulfur dioxide
(e) sulfide ion
(f) nitride ion
(g) dichromate ion
(h) permanganate ion.
6.
How would a chemistry student determine experimentally whether a substance contained
ionic or covalent bonds?
7.
Sodium will react with sodium nitrate in the presence of water to form the compound sodium
hyponitrite and also sodium hydroxide. The percentage composition of sodium hyponitrite is
(by mass) 43.4 % Na, 26.4 % N and 30.2 % O.
(a) What is the simplest formula for sodium hyponitrite?
(b) Given that the molecular formula of sodium hyponitrite contains 2 N atoms, what is the
molecular formula of this compound?
8.
Write balanced molecular and ionic equations for the reactions which occur in the following
experiments.
(a) Hydrochloric acid is added to solid calcium carbonate.
(b) Dilute nitric acid is added to solid sodium bicarbonate.
(c) Sulfuric acid is added to sodium hydroxide.
(d) Magnesium metal is added to nitric acid.
9.
White lead contains 81.5 % Pb, 15.73 % O and 2.36 % C . What is the empirical formula of
white lead?
10.
Why is the Law of Conservation of Mass considered to be valid in Chemistry?
11.
How many molecules of hydrogen are there in 1.01 x 10-3 g of hydrogen gas?
12.
What is the best method to separate the following and collect both?
(a) Two miscible liquids.
(b) A metal that is dissolved in a liquid.
(c) A precipitate.
(d) Two solids that are mixed (one is soluble).
Chemistry 2A/2B
13.
2
MgSO4. xH2O was heated and the following results obtained;
Mass of crucible and lid
Mass of crucible, lid and hydrated magnesium sulfate
Mass of crucible, lid and crystals after heating
Find the value of x.
Coghlan
= 14.636 g
= 15.336 g
= 14.978 g
14.
Nitrogen is excreted from the body in the chemical urea. Urea has the molecular formula
NH2CONH2. What is the percentage by mass of nitrogen in 1.00 mole of urea?
15.
Copper phthalocyanine is a complex organic molecule possessing a brilliant greenish-blue
colour. Millions of kg of this compound are produced each year to colour products such as
plastics, cars, rubber goods, printing inks, etc. Determine the percentage composition of this
compound given that its molecular formula is Cu(C8H4N2)4.
16.
Distinguish between the following pairs.
(a) Solvent and solute.
(b) Compound and mixture.
(c) Soluble and sparingly soluble.
(d) Ionisation and dissociation reactions.
17.
Write balanced ionic equations for each of the following reactions.
(a) Magnesium metal is added to hydrochloric acid producing magnesium chloride solution
and hydrogen gas.
(b) Barium nitrate solution is added to a sodium sulfate solution to produce barium sulfate
solid and a solution of sodium nitrate.
(c) Magnesium metal is burnt in oxygen gas to produce solid magnesium oxide.
(d) Phosphorous (P4) is burnt in oxygen gas to produce gaseous phosphorous pentoxide
(P4O10).
Chemistry 2A/2B
Mass of crucible, lid and crystals after further heating
What is the value of x in the formula?
Coghlan
= 14.978 g