Number of moles of a substance =
|
mass of substance in grams
|
relative atomic or formula mass
|
Concentration of solution, mol dm-3 =
|
number of moles of solute
|
volume of solution in dm3
|
Relative atomic masses: H = 1, C = 12, O = 16, Na = 23, Mg = 24, Ca = 40, Br = 80, Ag = 108, Au = 197
1 The number of moles of atoms in 12g of carbon and 108g of silver are the same. Explain this statement.
2 A pure gold wedding ring weighs 4g. How many moles of gold atoms are there in the ring?
3 The ingredients label on a packet of salted crisps says that it contains 0.23g of sodium. How many moles of sodium ions does this represent?
4 What is the mass of 2 moles of calcium carbonate?
5 A 0.75 dm3 bottle of ginger beer contains 14.1g of sucrose, C12H22O11.
a What is the relative formula mass of the sucrose?
b How many moles of sucrose are in the ginger beer?
c What is the concentration of the sucrose in the ginger beer in mol dm–?
Extra challenge
6 A sample of magnesium bromide (MgBr2) weighs 46g. How many moles of magnesium ions and bromide ions are in the sample?
What is a catalyst and how does it work?
Add a diagram to support your answer.
for Monday 21/09
CUS
Homework for Monday 2nd November:
For each substance below:
·
find the molecular formula using reference books
or the Internet
·
if the relative formula mass is given, show how
you can prove this
·
give a common use for the substance.
1 aspirin
2 citric
acid
3 ethanoic
acid
4 ethanol
5 paracetamol
6 phosphoric
acid
7 potassium nitrate
8 trinitrotoluene
(TNT)
Present your results in a table.
Extra challenge
9 The formula for a
compound X is CH3(CH2)7CH=CH(CH2)7CO2H.
a Work
out the molecular formula of this compound.
b Calculate
the relative formula mass of the compound.
c Deduce
the empirical formula of the compound.
d Find
out the name of the compound.
e Explain why this compound has been
described as ‘the smell of death’.
