Practice Chemistry Assessment.

For some of the following calculations you will need to refer to the Periodic Table.

Give answers to 3 significant figures where appropriate.
1
What is the mass of 0.126 moles of oxalic acid, H2C2O4? M(H2C2O4) = 90.0 g mol1
2
19.4 g of baking soda, NaHCO3, is dissolved in water to make exactly 1 litre of solution.
What is the concentration in mol L1? M(NaHCO3) = 84.0 g mol1
3
What amount (in moles) of sucrose is present in 14.0 mL of 0.450 mol L1 sucrose solution?
4
20.0 mL of a 0.0520 mol L–1 solution of NaOH was placed into a flask and diluted to 100 mL.
What is the concentration of the diluted solution?
5
Allicin, C6H10S2O, is the compound responsible for the characteristic smell of garlic.
Calculate the percentage of carbon and sulfur in this compound.
6
To carry out a colorimetric analysis a set of standard solutions are prepared from a
stock solution of 4.60 x 10–3 mol L1 FeCl3.6H2O.
What mass of FeCl3.6H2O is required to make up 500 mL of this solution?
7
The porphryn molecule forms an important part of the haemoglobin structure. This
porphryn molecule is 78.5% carbon, 3.2% hydrogen and 18.3% nitrogen, and has a molar mass of
306 g mol1.
Calculate both the empirical formula and the molecular formula of porphryn.
8
A precipitate of 1.34 g of Fe2O3 was obtained by treating a vitamin supplement dissolved in
water with NaOH and then heating. What is the mass of iron in the tablet?
9
10.0 g of iron was reacted with excess chlorine gas to produce iron chloride. The resulting
precipitate had a mass of 29.1 g.
Use this information to decide whether the product was iron(II) chloride, FeCl2, or iron(III)
chloride, FeCl3.
10
Hydrated magnesium chloride is heated in a crucible. The following data is collected:
mass of crucible and lid = 26.47 g
mass of crucible, lid and hydrated magnesium chloride = 28.62 g
mass crucible, lid and magnesium chloride after first heating = 27.49 g
mass of crucible, lid and magnesium chloride after second heating = 27.48 g
Use these results to determine the formula of hydrated magnesium chloride.
M(MgCl2) = 95.3 g mol1 M(H2O) = 18.0 g mol1
11
Wine makers convert sugars such as glucose to ethanol and carbon dioxide:
C6H12O6
2 C2H5OH + 2 CO2
M(C2H5OH) = 46.0 g mol1,
M(C6H12O6) = 180 g mol1
Starting with 540 g of glucose:
(a)
what is the mass of ethanol that can be obtained by this process?
(b)
what is the volume of ethanol that can be obtained by this process?
density of ethanol = 0.789 g mL1
12
In an experiment sodium hydroxide was used to prepare a sample of Glauber's salt,
Na2SO4.10H2O. The NaOH was neutralised with sulfuric acid and then the hydrated salt was
crystallised from the aqueous solution. The equation for the neutralisation reaction is:
H2SO4 + 2 NaOH
Na2SO4 + 2 H2O
Calculate the maximum mass of Glauber's salt, Na2SO4.10H2O, which could be made from
5.00 g of sodium hydroxide.
18
Atomic Number 1
1
H
1.0
2
3
4
Li
6.9
11
Na
23.0
19
K
39.1
37
Rb
85.5
55
Cs
133
87
Fr
223
Be
9.0
12
Mg
24.3
20
Ca
40.1
38
Sr
87.6
56
Ba
137
88
Ra
226
2
Molar Mass / g mol
–1
13
5
B
10.8
13
Al
3
4
5
6
7
8
9
10
11
12
27.0
21
22
23
24
25
26
27
28
29
30
31
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
45.0
47.9
50.9
52.0
54.9
55.9
58.9
58.7
63.5
65.4
69.7
39
40
41
42
43
44
45
46
47
48
49
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
88.9
91.2
92.9
95.9
98.9
101
103
106
108
112
115
71
72
73
74
75
76
77
78
79
80
81
Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
175
179
181
184
186
190
192
195
197
201
204
103
104
105
106
107
108
109
Lr
Rf
Db
Sg
Bh
Hs
Mt
262
57
Lanthanide Series
Actinide Series
58
59
La
Ce
Pr
139
140
141
89
90
91
Ac
Th
Pa
227
232
231
60
61
62
63
Nd
Pm
Sm
Eu
144
147
150
152
92
93
94
95
U
Np
Pu
Am
238
237
239
241
14
15
16
17
6
7
8
9
C
12.0
14
Si
28.1
32
Ge
72.6
50
Sn
119
82
Pb
207
N
14.0
15
P
31.0
33
As
74.9
51
Sb
122
83
Bi
209
O
16.0
16
S
32.1
34
Se
79.0
52
Te
128
84
Po
210
F
19.0
17
Cl
35.5
35
Br
79.9
53
I
127
85
At
210
64
65
66
67
68
Gd
Tb
Dy
Ho
Er
157
159
163
165
167
96
97
98
99
100
Cm
Bk
Cf
Es
Fm
247
249
251
254
257
69
70
Tm
Yb
169
173
101
102
Md
No
258
255
He
4.0
10
Ne
20.2
18
Ar
40.0
36
Kr
83.8
54
Xe
131
86
Rn
222