CHEMISTRY WORKSHEET
Section 1g: Stoichiometry
Part A: Chemical Formulae
1.
2.
Write the chemical formula for the following compounds.
a)
potassium carbonate
b)
dinitrogen tetroxide
c)
magnesium hydroxide
d)
iron(III) chloride
e)
tin(IV) oxide
f)
carbon tetrachloride
g)
potassium permanganate
h)
ammonium dichromate
i)
potassium hydrogen phosphate
j)
sodium hydrogen sulfate
Name the following compounds from the chemical formulas.
a)
AgCl
b)
KOH
c)
AgNO3
d)
UF6
e)
SF6
f)
Ca3(PO4)2
g)
KHCO3
h)
Fe2O3
i)
Cu(NO3)2
j)
H2CO3
Part B: Chemical Equation
3.
Balance the following equations. Then, classify each reaction as synthesis,
decomposition, single replacement, double replacement or combustion.
(i)
____ Sb + ____ Cl2 → ____ SbCl2
(ii)
____ Pb(NO3)2 + ____ H2S → ____ PbS + ____ HNO3
(iii)
____ C5H12 + ____ O2 → ____ CO2 + ____ H2O
(iv)
____ CuSO4 → ____ CuO + ____ SO2 + ____ O2
(v)
____ Fe + ____ HCl → ____ FeCl2 + ____ H2
(vi)
____ Co + ____ H2SO4 → ____ CoSO4 + ____ H2
(vii)
____ NH3 + ____ O2 → ____ NO + ____ H2O
(viii)
____ PCl5 + ____ H2O → ____ H3PO4 + ____ HCl
(ix)
____ Fe2O3 + ____ SO3 → ____ Fe2(SO4)3
(x)
____ B2H6 + ____ O2 → ____ B2O3 + ____ H2O
(xi)
____ Al + ____ O2 → ____ Al2O3
(xii)
____ H2O2 → ____ H2O + ____ O2
(xiii)
____ HClO4 + ____ P4O10 → ____ H3PO4 + ____ Cl2O7
(xiv)
____ Au2S3 + ____ H2 → ____ Au + ____ H2S
(xv)
____ Ba3N2 + ____ HF → ____ BaF2 + ____ NH3
(xvi)
____ Mg + ____ N2 → ____ Mg3N2
(xvii) ____ NaClO3 → ____ NaCl + ____ O2
(xviii) ____ CuO + ____ H2 → ____ Cu + ____ H2O
(xix)
____ C12H22O11 + ____ O2 → ____ CO2 + ____ H2O
(xx)
____ FeS + ____ O2 → ____ Fe2O3 + ____ SO2
4.
Write a balance equation for the following chemical reactions. Include state symbols.
(i)
Tin metal react with bromine liquid to produce a solid of tin(VI) bromide.
(ii)
Calcium chloride solution is added to a beaker containing equal volume of sodium
phosphate to produce a precipitate of calcium phosphate and sodium chloride
solution.
(iii)
Ammonium sulfate solid is added to a test tube and is heated. The solid decomposed
into ammonia gas and sulfuric acid.
(iv)
Aluminium metal reacts with sulfuric acid to produce aluminium sulfate solution and
hydrogen gas.
(v)
Potassium hydroxide solution react with phosphoric acid to produce potassium
phosphate solution and water.
(vi)
Sodium oxide solid react with water to form sodium hydroxide solution.
(vii)
Tin(II) oxide solid react with carbon to produce tin metal and carbon monoxide gas.
(viii)
Ammonia gas react with oxygen gas to form nitrogen gas and steam.
(ix)
Sugar (C12H22O11) is heated and decomposes into carbon and water.
(x)
Zinc metal react with silver nitrate solution to produce silver metal and zinc nitrate
solution.
Part C: Relative masses
5.
Find the formula or molar mass of the following substances:
a)
CO2
b)
Ca3(PO4)2
c)
Al2O3
d)
KCl
e)
C6H10O5
f)
C12H22O11
g)
ZnCl2
h)
AgNO3
i)
calcium oxide
j)
propane, C3H8
k)
magnesium nitrate
l)
copper(II) carbonate
m)
nitric acid
n)
aluminium hydroxide
o)
copper(II) nitrate
p)
hydrogen cyanide
Part D: Moles
6.
What is the mass of the following substances?
a)
1 mole of carbon atoms
b)
3 moles of sodium atoms
c)
0.1 mole of magnesium atoms
d)
2 moles of sulfur atoms
e)
0.5 mole of calcium atoms
f)
0.01 mole of silicon atoms
g)
2 moles of propane
h)
0.5 mole of carbon dioxide
i)
0.1 mole of nitric acid
j)
10 moles of calcium oxide
k)
1 mole of oxygen molecule
l)
2.5 moles of Na2O
m)
2.34 moles of platinum
n)
2 moles of
238
U
7.
8.
How many moles are there in the substances?
a)
54 g of aluminium
b)
4 g of argon
c)
36 g of beryllium
d)
71 g of chlorine
e)
0.635 g of copper
f)
120 g of calcium
g)
375 g of CaCO3
h)
79 g of Fe2O3
i)
132 g of CO2
j)
58.5 g of sodium chloride
What are the relative atomic masses of the following? Which element is each one?
a)
3 moles of atoms has a mass of 3 g
b)
0.02 mole of atoms has a mass of 3.94 g
c)
4.38 mole of atoms has a mass of 582.54 g
d)
0.25 mole of atoms has a mass of 9.75 g
e)
0.01 mole of atoms has a mass of 0.56 g
f)
2 mole of atoms has a mass of 11 g
9.
g)
0.125 mole of atoms has a mass of 14.88 g
h)
0.5 moles of atoms has a mass of 40 g
i)
0.17 mole of atoms has a mass of 15.47 g
j)
0.1 mole of atoms has a mass of 3.2 g
Use you answer in Question 7 to solve this.
a)
How many atoms of aluminium are there in 54 g of aluminium?
b)
How many atoms of chlorine are there in 71 g of chlorine?
c)
How many oxygen ion are there in 375 g of CaCO3?
d)
How many iron ion are there in 79 g of Fe2O3?
e)
How many atoms of carbon are there in 132 g of CO2?
10. This question is about the molarity of some aqueous solutions. Complete the following table.
Show your working in the space provided.
solute
mass (g)
volume (dm3)
molarity (mol/dm3)
a)
LiBr
43.3
0.5
b)
NH4Cl
160.2
4.0
c)
NaCl
146.0
25.0
d)
BaCl2
385.5
2.5
e)
KCl
37.5
0.125
f)
NaOH
80.0
1.6
g)
CuSO4
1.6
0.125
h)
Al(NO3)3
0.5
0.6
i)
(NH4)2SO4
0.3
2.0
11. a)
Use you answer in Question 7 to find the volume of:
(i)
chlorine
(ii)
carbon dioxide
b)
392 dm3 of a gas are dissolved in 2.65 dm3 of a solvent. What is the concentration of
the resulting solution?
c)
48 dm3 of a gas has a mass of 262 g. How many moles is this? What is the Mr? What
must this element be?
d)
1.24 g of calcium carbonate is reacted with 15 cm3 of 1.0 mol/dm3 hydrochloric acid.
What is the volume of carbon dioxide formed? How many atoms are there in this gas?
e)
A gas has a volume of 120 dm3, how many moles is this?
f)
3.0 dm3 of a gas weighs 2.0 g. What is the Mr?
g)
How many atoms of hydrogen are in 67.2 dm3 of H2 at RTP?
h)
i)
Calculate the mass of the following:
Note: 1 mole of any gas occupies 24 dm3 at room temperature and pressure (RTP)
(i)
48 000 cm3 of hydrogen: H2
(ii)
12 dm3 of carbon dioxide: CO2
(iii)
6 dm3 of propane: C3H8
(iv)
100 cm3 of hydrogen: H2
(v)
400 cm3 of hydrogen chloride: HCl
(vi)
40 cm3 of oxygen: O2
(vii)
175 cm3 of ammonia: NH3
(viii)
2.5 dm3 of argon: Ar
Magnesium metal burns completely in excess oxygen to form a white solid of
magnesium oxide.
(i)
Write a balanced chemical equation for this reaction. Include state symbols.
(ii)
What mass of magnesium oxide is produced if 6g of magnesium is used in this
reaction?
(iii)
What volume of oxygen is needed to react exactly with 12g of magnesium?
j)
When sodium hydrogencarbonate is heated, it forms carbon dioxide gas.
2NaHCO3 (s)  Na2CO3 (aq) + H2O (l) + CO2(g)
k)
(i)
Calculate the minimum mass of sodium hydrogencarbonate that must be heated
to produce 0.25dm3 of the gas.
(ii)
Calculate the mass, in grams, of carbon dioxide that would be produced by
completely decomposing 10.5g of sodium hydrogencarbonate.
The manufacturer makes a batch of ethanoic acid from methanol and carbon
monoxide using this reaction.
CH3OH + CO  CH3COOH
He starts with 64kg of methanol.
Calculate the maximum mass of ethanoic acid he could obtain.
l)
Mortar contains calcium hydroxide and is used to join bricks together when building
walls.
The calcium hydroxide in mortar reacts with carbon dioxide from the atmosphere to
form calcium carbonate. Calcium oxide formed when calcium carbonate is strongly
heated. Water is then added to calcium oxide to form calcium hydroxide.
CaO (s) + H2O (l)  Ca(OH)2 (s)
Calculate the mass of water need to react with calcium oxide when 28 kg of calcium
carbonate is heated. What will be the minimum mass of calcium hydroxide formed
from this reaction?
m)
Lead can be extracted from lead(II) sulfide, PbS, where it will be heated in air to
produce lead(II) oxide and sulfur dioxide. Lead(II) oxide is then heated with coke in a
blast furnace to give lead.
2PbO (s) + C (s) → 2Pb (s) + CO2 (g)
Calculate the minimum mass, in tonnes, of coke needed to react with 44.6 tonnes of
lead(II) oxide.
[1 tonne = 106 g]
Part E: Empirical and molecular formula
12. Work out the empirical (simplest) formula for when the following elements react:
a)
27.9g of iron and 35.5g of chlorine
b)
48.6g of magnesium with oxygen to produce 80.6g of magnesium oxide
c)
20 g of calcium was found to react with 35·5 g of chlorine.
d)
33.6 g of iron was found to react with 14.4 g of oxygen.
e)
Copper pyrites is an ore of copper that contains copper, iron and sulfur. The
percentage composition by mass of copper pyrites is
Cu 34.60%
f)
Fe 30.52%
S
34.88%
A titanium ore contains the composition by mass
Ti = 31.6%
Fe = 36.8%
O = 31.6%
Show by calculation that the empirical formula of this ore is FeTiO3
g)
Suppose 6.25g of blue hydrated copper(II) sulphate, CuSO4.xH2O, (x unknown) was
gently heated in a crucible until the mass remaining was 4.00g. This is the white
anhydrous copper(II) sulphate. Find the value of x.
13. Work out the molecular formula of the compounds for the following:
a)
A compound was found to contain 3.0 g of carbon and 0.5 g of hydrogen. The relative
molecular mass of the compound is 42.
b)
A compound was found to contain 48 g of carbon and 12 g of hydrogen. The relative
molecular mass of the compound is 30.
c)
A sample of a chlorofluorocarbon (CFC) contains 0.24 g of carbon, 0.38 g of fluorine
and 1.42 g of chlorine. The relative formula mass of the CFC is 204.
d)
Compound X is made from ethene and is used in cars to prevent the engine coolant
from freezing in cold water. It contain 38.7% carbon, 9.7% hydrogen and 51.6%
oxygen by mass. The relative formula mass of X is 62.
h)
A sample of a aluminium chloride contains 9g of aluminium and 35.5g of chlorine. The
relative molecular mass of the aluminium chloride is 259.
Part F: Percentage yield and purity
14. a)
For the following equations work out what the percentage yield is if 15g of the metal
produces the mass of product shown in brackets after the equation:
(i)
Fe + Cl2  FeCl2 (30g)
(ii)
4Al + 3O2  2Al2O3
(17g)
(iii)
Ni + S  NiS
(iv)
4K + O2  2K2O (18g)
(22g)
b)
What would be the % yield if the reaction in 11(i) had produced only 2.5g of
magnesium oxide?
c)
Potassium iodide is reacted with lead nitrate. The expected yield is 20 g, but only 18 g
was made. What is the percentage yield?
d)
A reaction produces 48 g of copper oxide, the predicted yield was 64 g. What is the
percentage yield of this reaction?
e)
What is the percent yield for a reaction if you predicted the formation of 21g of C6H12
and actually recovered only 3.8g?
f)
Iron is extracted from iron oxide in the blast furnace:
Fe2O3 + 3CO → 2Fe + 3CO2
(i)
Calculate the maximum theoretical mass of iron that can be made from 100g of
iron oxide.
(ii)
In the reaction, only 65 g of iron was made. Calculate the % yield.
15. a)
1.56g of impure sodium sulfate sample produces 2.15g of barium sulfate precipitate
when the sample reacts with barium chloride. Find the mass of pure sodium sulfate
containing in the sample and calculate the percentage purity.
b)
0.50g of impure sodium chloride sample yields 1.15g of silver chloride precipitate when
the sample reacts with silver nitrate. Find the mass of pure sodium chloride containing
in the sample and calculate its percentage purity.
c)
Consider the reaction:
4KO2(s) +2CO2(g)  2K2CO3(s) +3O2(g)
(i)
A 30.0g sample of potassium oxide is 59.3% pure. What mass of potassium
carbonate can the sample produce?
(ii)
Another sample of potassium oxide with a mass of 150.0g is reacted so as to
produce 89.7g of potassium carbonate. What is the percentage purity of the
potassium oxide?
(iii)
What mass of potassium oxide with a purity of 64.8% is needed to make 100.0g
of potassium carbonate?