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Title: Chemistry problem solutions
Description: It is a solution for all chemistry problems with solution
Description: It is a solution for all chemistry problems with solution
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CHEM1001 Answers to Problem Sheet 5
1
...
9 g and consists of 6
...
The mass of
12 × 1023 atoms is therefore:
mass =
𝟏𝟐×𝟏𝟎𝟐𝟑
𝟔
...
9 g mol-1 = 220 g
As the number of atoms is only known to 2 significant figures, this mass should be
rounded to 220 g
...
003 g so 6 moles has a mass of 6 × 4
...
018 g
...
00 has two trailing zeros
indicating that it has been measured this accurately)
...
0 g
...
0 g) < copper (100 g) < silver (220 g)
2
...
01 (C)) + (4 × 1
...
052 g mol-1
The number of moles in 112 g of C2H4 is therefore:
number of moles of C2H4 =
𝐦𝐚𝐬𝐬
𝐦𝐨𝐥𝐚𝐫 𝐦𝐚𝐬𝐬
=
𝟏𝟏𝟐 𝐠
𝟐𝟖
...
99 mol
The mass of 112 g is known to 3 significant figures and so the answer is also given to this
level of accuracy
...
Each mole of C2H4
is made up of 2 moles of C and 4 moles of H:
number of moles of C = 2 × 3
...
98 mol
Again, the figure has been rounded to reflect the three significant figures given for the
mass of ethylene
...
The molar mass of C4H10 is ((4 × 12
...
008 (H))) g mol-1 = 58
...
0 g of C4H10 is therefore:
number of moles of C4H10 =
𝐦𝐚𝐬𝐬
𝐦𝐨𝐥𝐚𝐫 𝐦𝐚𝐬𝐬
The equation for the combustion is:
C4H10(g) +
13
O2 à 4CO2(g) + 5H2O(l)
2
=
𝟏𝟎
...
𝟏𝟐 𝐠 𝐦𝐨𝐥!𝟏
= 0
...
2
(i)
The number of moles of CO2 produced is therefore 4 × 0
...
688 mol
...
01 (C) + 2 × 16
...
01 g mol-1
...
688 mol of CO2 is:
mass of CO2 = number of moles × molar mass = 0
...
01 g mol-1 = 30
...
(ii)
The number of moles of H2O produced is 5 × 0
...
860 mol
...
008 (H) + 16
...
016 g mol-1
...
860 mol of H2O is:
mass of H2O = number of moles × molar mass = 0
...
016 g mol-1 = 15
...
(iii)
13
× 0
...
118 mol
...
00) g mol-1 = 32
...
The mass of 1
...
118 mol × 32
...
8 g
...
Sodium carbonate is Na2CO3 and has a formula mass of
formula mass = (2×22
...
01 (C) + 3×16
...
99 g mol-1
The number of moles in 53
...
𝟎 𝐠
𝟏𝟎𝟓
...
500 mol
The reaction is:
2NaOH + CO2 à Na2CO3 + H2O
Two moles of NaOH are required for every mole of Na2CO3 that is prepared
...
500
moles of Na2CO3 therefore requires 1
...
Each mole of NaOH has a mass of 22
...
00 (O) + 1
...
998 g mol-1
...
00 mol of NaOH is:
mass of NaOH = number of moles × molar mass
= (39
...
00 g mol-1) = 40
...
Note that the mass of sodium carbonate is given in the question as 53
...
It is therefore
known to 3 significant figures and the accuracy given in the answer reflects this
...
Metals form the majority of the elements in the Periodic Table and occur on the left side
of the Table
...
There are a few
mettaloids or semi-metals on the border between metals and non-metals
...
6
Title: Chemistry problem solutions
Description: It is a solution for all chemistry problems with solution
Description: It is a solution for all chemistry problems with solution