Stoichiometry – chemical calculations - Chemistry - page 71

Stoichiometry - chemical calculations

● Additional questions
Use the data in the table below to answer the
questions which follow.

a Name the reducing agent in this process.
b Name the oxide of iron shown in the equation.
c Explain why this is a redox reaction.
d Calculate the mass of iron which will be
produced from 640 tonnes of haematite.
7 Consider the following information about the newly
discovered element, vulcium, whose symbol is Vu.
'Vulcium is a solid at room temperature. It is easily cut
by a penknife to reveal a shiny surface which tarnishes
quite rapidly. It reacts violently with water, liberating a
flammable gas and forms a solution with a pH of 13.
When vulcium reacts with chlorine, it forms a white
crystalline solid containing 29.5% chlorine.'
( A r : Vu = 85)
a Calculate the empirical formula of vulcium
chloride.
b To which group of the Periodic Table (p. 136)
should vulcium be assigned?
c Write a word and balanced chemical equation for
the reaction between vulcium and chlorine.
d What other information in the description
supports the assignment of group you have given
to vulcium?
e What type of bonding is present in vulcium
chloride?
f Write a word and balanced chemical equation for
the reaction between vulcium and water.
g Write the formulae for:
(iii) vulcium sulfate
(iii) vulcium carbonate
(iii) vulcium hydroxide.
Look at the Periodic Table (p. 294) to find out the
real name of vulcium.
8 0.048 g of magnesium was reacted with excess
dilute hydrochloric acid at room temperature and
pressure. The hydrogen gas given off was collected.
a Write a word and balanced symbol equation for
the reaction taking place.
b Draw a diagram of an apparatus which could be
used to carry out this experiment and collect the
hydrogen gas.
c How many moles of magnesium were used?
d Using the equation you have written in your answer
to a , calculate the number of moles of hydrogen
and hence the volume of this gas produced.
e Calculate the volume of a solution containing
0.1 mol dm −3 hydrochloric acid which would
be needed to react exactly with 0.048 g of
magnesium.

Element A r
H 1
C 12
N 14
O 16
Na 23
Mg 24
Si 28
S 32
Cl 35.5
Fe 56
1 Calculate the mass of:
a 1 mole of:
(iii) chlorine molecules
(iii) iron( iii ) oxide.
b 0.5 mole of:
(iii) magnesium nitrate
(iii) ammonia.
2 Calculate the volume occupied, at rtp, by the
following gases. (One mole of any gas occupies a
volume of 24 dm 3 at rtp.)
a 12.5 moles of sulfur dioxide gas.
b 0.15 mole of nitrogen gas.
3 Calculate the number of moles of gas present in
the following:
a 36 cm 3 of sulfur dioxide
b 144 dm 3 of hydrogen sulfide.
4 Use the following experimental information to
determine the empirical formula of an oxide of
silicon.
Mass of crucible 18.20 g
Mass of crucible + silicon 18.48 g
Mass of crucible + oxide of silicon 18.80 g
5 a Calculate the empirical formula of an organic
liquid containing 26.67% of carbon and 2.22% of
hydrogen, with the rest being oxygen.
b The M r of the liquid is 90. What is its molecular
formula?
6 Iron is extracted from its ore, haematite, in the
blast furnace. The main extraction reaction is:
Fe 2 O 3 ( s ) + 3CO( g ) → 2Fe( s ) + 3CO 2 ( g )