U1L7 Assignment Key

```Assignment U1L7 Key
Writing Formula Equations from Word Equations (82 marks)
In the following exercises, recall that many of the non-metal elements exist as molecules, such as
H2(g) or S8(s). Refer to Table A2.9 on page 48 of Science 10 for the chemical formulas of molecular
elements.
1. Rewrite the following word equations as formula equations and then balance them: (36 marks)
a)solid sodium metal reacts with chlorine gas to produce solid sodium chloride (3 marks)
2 Na(s)+Cl2(g)  2 NaCl(s)
b) solid potassium metal reacts with oxygen gas to produce solid potassium oxide (3 marks)
4 K(s) + O2(g)  2 K2O(s)
c) hydrogen gas reacts with oxygen gas to produce liquid water (3 marks)
2 H2(g) + O2(g)  2 H2O(l)
d) solid potassium chlorate decomposes into oxygen gas and solid potassium chloride
(3 marks)
2 K(ClO3)(s)  3 O2(g) + 2 KCl (s)
e) solid aluminium oxide is decomposed into solid aluminium and oxygen gas (3 marks)
2 Al2O3 (s)  4 Al(s) + 3 O2(g)
f)
mercury(II) sulphide is decomposed into liquid mercury and solid sulphur (3 marks)
8 HgS(s)  8 Hg(l) + S8(s)
g) aqueous cobalt(III) nitrate reacts with solid zinc to produce aqueous zinc nitrate and solid
cobalt (3 marks)
2 Co(NO3)3(aq) + 3 Zn(s)  3 Zn(NO3)2(aq) +2 Co(s)
33
h) fluorine gas reacts with aqueous lead(IV) iodide to produce aqueous lead(IV) fluoride and
solid iodine (3 marks)
2 F2(g) + PbI4(aq)  PbF4(aq) + 2 I2(s)
i)
aqueous gold(III) bromide reacts with solid silver metal to produce solid silver bromide
and solid gold metal (3 marks)
AuBr3(aq) + 3 Ag(s) + 3 AgBr(s) + Au(s)
j)
aqueous sodium sulphate reacts with aqueous strontium hydroxide to produce aqueous
sodium hydroxide and solid strontium sulphate (3 marks)
Na2(SO4)(aq) + Sr(OH)2(aq)  2 NaOH(aq) + Sr(SO4)(s)
k) aqueous thallium(I) hydroxide reacts with aqueous magnesium bromide to produce solid
magnesium hydroxide and solid thallium bromide
2 Tl(OH)(aq) + MgBr2(s)  Mg(OH)2(s) + 2 TlBr(s)
l)
methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapour
CH4(g) +2 O2(g)  CO2(g) +2 H2O(g)
34
2. Rewrite the following word equations as formula equations and balance: (30 marks)
a) magnesium metal reacts with liquid bromine to produce magnesium bromide (3 marks)
Mg(s) + Br2(l)  MgBr2(s)
b) solid sulfur and hydrogen gas react to produce hydrogen sulfide gas (3 marks)
S8(s) + 8 H2(g)  8 H2S(g)
c) methane gas reacts with liquid water to produce liquid methanol and hydrogen gas (3
marks)
CH4 (g) + H2O (l)  CH3OH(l) + H2(g)
d) aqueous copper(II) chloride reacts with nickel metal to produce copper metal and
nickel(III) chloride (3 marks)
3 CuCl2(aq) + 2 Ni(s)  3 Cu(s) + 2 NiCl3(aq)
e) aqueous barium chlorate reacts with aqueous cesium sulfate to produce
cesium chlorate and barium sulfate (3 marks)
Ba(ClO3)2(aq) + Cs2(SO4)(aq)  2 Cs(ClO3)(aq) + Ba(SO4)(aq)
f)
a potassium carbonate solution reacts with a sodium chloride solution to produce
potassium chloride and sodium carbonate (3 marks)
K2(CO3)(aq) +2 NaCl (aq) 2 KCl (s) + Na2(CO3)(aq)
g) solid sucrose burns in oxygen gas to produce carbon dioxide gas and water vapour
(3 marks)
C12H22O11(s) + 12 O2(g)  12 CO2(g) + 11 H2O(g)
h) aqueous hydrogen peroxide decomposes into oxygen gas and water (3 marks)
2 H2O2(aq)  O2(g) + 2 H2O(l)
i)
hydrochloric acid reacts with aqueous sodium hydroxide to produce
aqueous sodium chloride and water (3 marks)
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
j)
sulfuric acid reacts with solid aluminium hydroxide to produce aluminium sulfate
and water (3 marks)
3 H2SO4(aq) + 2 Al(OH)3(s)  Al2(SO4)3(aq) +6 H2O(l)
35
Balancing Formula Equations 1Balance the following chemical
equations: (16 marks)
a)
___4__ Na(s) + __1___ O2(g)  ___2__ Na2O(s)
b)
___2__ Al(s) + ___3__ Cl2(g)  __2___ AlCl3(s)
c)
___1__ N2(g) + __2___ O2(g)  ___2__ NO2(g)
d)
__2___ HI(g)  ___1__ H2(g) + __1___ I2(s)82
e)
__2___ NH3(g)  ___3__ H2(g) + _1____ N2(g)
f)
__8___ Al2S3(s)  __16___ Al(s) + __3___ S8(s)
g)
___2__ BN(s) + ___3__ Cl2(g)  ___2__ BCl3(g) + __1___ N2(g)
h)
__3___ SnF4(aq) + __4___ Cr(s)  __4___ CrF3(aq) + __3___ Sn(s)
i)
__1___ Mg(s) + ___2__ HCl(aq)  ___1__ MgCl2(aq) + ___1__ H2(g)
j)
___2__ (NH4)3PO4(aq) + ___3__ CaBr2(aq)  ___1__ Ca3(PO4)2(s) + __6__ NH4Br(aq)
k)
__1___ Pb(NO3)4(aq) + ___2__ K2Cr2O7(aq)  ___1__ Pb(Cr2O7)2(s) + ___4__ KNO3(aq)
l)
___3__ AgClO4(aq) + ___1__ Na3PO4(aq)  __3___ NaClO4(aq) + ___1__ Ag3PO4(s)
m)
__2___ HCl(aq) + ___1__ Ca(OH)2(s)  __1___ CaCl2(aq) + __2___ H2O(l)
n)
___2__ CH3COOH(aq) + ___1__ Ba(OH)2(aq)  ___1__ Ba(CH3COO)2(aq) + ___2__ H2O(l)
o)
__2___ C3H8(g) + __5___ O2(g)  __6___ CO2(g) + ___8__ H2O(g)
p)
__2___ C6H14(l) + __19___ O2(g)  __12___ CO2(g) + ___14__ H2O(g)