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Chemistry 1010
Test # 3
[50 Marks Total]
March 20, 2003
Name: _____________________ Lab. Slot ____ MUN #: ______________________
Show your calculations for Parts B and C and give numerical answers to the correct
number of significant digits.
Marking Scheme
QUESTIONS
VALUE
MARK
Part A
16
Part B
18
Part C
16
Total
Part A
[Total Marks 16]
Multiple choice questions
Circle the letter for the one correct answer. [Each Question = 2 marks]
1.
The correct order for the atoms and ions,
Cl, S2-, K+, Se2–
arranged in order of increasing radius (smallest first) is
(a)
(b)
(c)
(d)
(e)
2.
When 50.0 g of a mixture of copper and magnesium were allowed to react with dilute
sulfuric acid, the magnesium dissolved
Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)
leaving the copper unchanged and giving 2.00 g of hydrogen gas, H2(g). What was the
percentage by weight of copper in the mixture?
(a)
(b)
(c)
(d)
(e)
3.
2.00%
24.3%
4.00%
48.2%
51.8%
An sample of 1.040 g of Ca(OH)2(s) (molar mass = 74.09 g mol-1) required 59.30 mL of a
solution of hydrochloric acid, HCl(aq), for neutralization in the reaction
2 HCl(aq) + Ca(OH)2(s) → CaCl2(aq) + 2 H2O(l).
Base on these results, what is the concentration of the hydrochloric acid solution?
(a)
(b)
(c)
(d)
(e)
4.
Cl < S2- < K+ < Se2–
S2- < Cl < K+ < Se2–
Se2– < S2- < Cl < K+
Cl < K+ < S2- < Se2–
K+ < Cl < S2- < Se2–
0.02807 mol L-1
0.2367 mol L-1
0.4734 mol L-1
1.665 x 10-3 mol L-1
4.734 x 10-4 mol L-1
Which of the following atoms is the most electronegative?
(a)
(b)
(c)
(d)
(e)
Na
Cs
P
As
O
-1-
CHEMISTRY 1010
5.
Which of the following diagrams correctly represents the ground state orbital occupancy
for the outer electrons of a silicon atom?
3s
(a)
(b)
(c)
(d)
(e)
6.
↑
↑
↑↓
↑↓
↑↓
↑
↑ ↑
↑ ↑
↑ ↑
The electron configuration for the positive ion present in iron(III) chloride, FeCl3, in the
ground state is
(a)
(b)
(c)
(d)
(e)
7.
↑↓
↑
↑↓
↑↓
3p
1s2
1s2
1s2
1s2
1s2
2s22p6
2s22p6
2s22p6
2s22p6
2s22p6
3s23p63d6 4s2
3s23p63d5
3s23p63d8
3s23p63d9 4s2
3s23p63d3 4s2
The following mixtures are made as listed in the table below:
Mixture
A
B
C
D
E
F
Mixture (1 mL each of 0.1 mol L-1 solutions)
K2SO4(aq)
NaCl(aq)
AgNO3(aq)
BaCl2(aq)
K2SO4(aq)
NaOH(aq)
K2SO4(aq)
BaCl2(aq)
CuSO4(aq)
NaOH(aq)
BaCl2(aq)
NH4NO3(aq)
The three mixtures that give precipitates are
(a)
(b)
(c)
(d)
(e)
8.
A, C and F
A, C and D
B, D and E
B, D and F
D, E and F
One of the spectral lines in the spectrum of a mercury vapour lamp has a wavelength of
435.8 nm. If the velocity of light is 3.00 x 108 m s-1, what is the frequency of the light
associated with the spectral line?
(a)
(b)
(c)
(d)
(e)
1.31 x 102 s-1
1.45 x 10-15 s-1
2.89 x 10-40 s-1
6.88 x 1014 s-1
6.88 x 105 s-1
Section B
(18 Marks)
B1
[3]
(a)
(b)
[2]
Fill in the blanks in the following table
subshell
orbitals (allowed
(value of l )
value(s) of ml )
total electrons
allowed
in the subshell
3
0
0
2
3
2
-2,-1, 0,+1,+2
10
orbital
description
shell
(value of n)
3s
3d
Give the number of unpaired electrons present the following atoms in the
ground state.
(i)
(ii)
(iii)
Si
Ar
As
__2___
___0__
__3___
-2-
CHEMISTRY 1010
B2
[3]
A solution of sodium hydroxide, NaOH, was prepared by dissolving some of the
pure solid in water and making the solution up to 250.00 mL.
(a)
The sodium hydroxide solution was standardized against hydrochloric
acid. 25.00 mL of 0.1045 mol L-1 hydrochloric acid required 19.26 mL of
the sodium hydroxide for neutralization. Write the equation for the reaction
and calculate the concentration of the sodium hydroxide solution.
HCl(aq) + NaOH(aq) Æ NaCl(aq) + H2O(l)
Moles of HCl used = (25.00 x 10-3 L) x 0.1045 mol L-1 = 2.6125 x 10-3 mol
Since 1 mole of HCl(aq) reacts with 1 mole of NaOH(aq)
the concentration of the NaOH =
Ans: 0.1356 mol L-1
(b)
[3]
The sodium hydroxide solution (use the concentration calculated above)
was then used to titrate a solution of sulfuric acid of unknown
concentration. 25.00 mL of the sulfuric acid solution required 37.45 mL of
the sodium hydroxide solution for neutralization. Write the equation for the
reaction and c
H2SO4(aq) + 2 NaOH(aq) Æ Na2SO4(aq) + 2 H2O(l)
NaOH used = (37.45 x 10-3 L) x 0.13564 mol L-1 = 5.0799 x 10-3 mol
Focus on NaOH: ½ H2SO4(aq) + NaOH(aq) Æ ½ Na2SO4(aq) + H2O(l)
Moles of H2SO4 = ½ x 5.0799 x 10-3 mol so the
concentration of the H2SO4 =
Ans: 0.1016 mol L-1
(c)
[4]
2.6125%10 −3 mol
-1
19.26%10 −3 L = 0.13564 mol L
½ % 5.0799%10−3 mol
= 0.10160 mol L-1
25.00 %10−3 L
Calculate the mass of sodium hydroxide that was dissolved in water to
make the original 250.00 mL of solution (use the concentration calculated
above) .
Moles of NaOH in the solution = 0.13564 mol L-1 x 250.00 x 10-3 L
= 0.033910 mol
so mass of NaOH = 0.033910 mol x (15.9994 + 22.9898 + 1.0079) g mol-1
= 1.3563 g
Ans: 1.356 g
B3. Complete the following table.
[3]
Symbol of
Element or
ion
Number of
protons in
nucleus
Se
34
[ Ar ] 4s2 3d10 4p4
Al3+
13
[He] 2s22p6
Cr
24
[Ar]4s1 3d5
Ground state electron configuration
(abbreviated notation)
-3-
CHEMISTRY 1010
Section C
(16 Marks)
C1.
Balance the following redox reaction
ClO–(aq) + S(s) Æ Cl2(aq) + SO32–(aq)
(a)
[6]
in acidic solution
4 H+(aq) + 2 ClO–(aq) + 2 e- Æ Cl2(aq) + 2 H2O(l)
4 H2O(l) + S(s) Æ SO42–(aq) + 8 H+(aq) + 6 e3 x (4 H+(aq) + 2 ClO–(aq) + 2 e- Æ Cl2(aq) + 2 H2O(l))
Ans: 4 H+(aq) + 6 ClO–(aq) + S(s) Æ 3 Cl2(aq) + SO42–(aq) + 2 H2O(l)
[5]
C2.
(b)
in basic solution
4 OH-(aq)+ 4 H+(aq) + 6 ClO–(aq) + S(s)Æ 3 Cl2(aq) + SO42–(aq) + 2 H2O(l)) + 4 OH-(aq)
4 H2O(l) + 6 ClO–(aq) + S(s) Æ 3 Cl2(aq) + SO42–(aq) + 2 H2O(l) + 4 OH-(aq)
Ans: 2 H2O(l) + 6 ClO–(aq) + S(s) Æ 3 Cl2(aq) + SO42–(aq) + 4 OH-(aq)
Write balanced molecular and balanced net-ionic equations for two of the
following reactions below.
[5]
(a)
Magnesium metal reacts with dilute hydrochloric acid to give hydrogen
gas.
Mg(s) + 2 H2O(l)Æ Mg(OH)2(aq) + H2(g)
Mg(s) + 2 H2O(l)Æ Mg2+(aq) + 2 OH-(aq) + H2(g)
(b)
Solid calcium carbonate reacts with dilute nitric acid to give carbon dioxide
gas.
CaCO3(s) + 2 HNO3(aq)Æ Ca(NO3)2(aq) + CO2(g) + H2O(l)
CaCO3(s) + 2 H+(aq)Æ Ca2+(aq) + CO2(g) + H2O(l)
(c)
Potassium sulfate solution reacts with lead(II) nitrate solution to give a
white precipitate.
K2SO4(aq) + Pb(NO3)2(aq)Æ PbSO4(s) + 2 KNO3(aq)
SO42-(aq) + Pb2+(aq)Æ PbSO4(s)
-4-