# 1. What is the sum of all coefficients when the following... possible whole numbers?

## Transcription

1. What is the sum of all coefficients when the following... possible whole numbers?
```1.
What is the sum of all coefficients when the following equation is balanced using the smallest
possible whole numbers?
__ C2H2 + __O2 → __CO2 + __H2O
A.
5
B.
7
C.
11
D.
13
(Total 1 mark)
2.
1.7 g of NaNO3 (Mr = 85) is dissolved in water to prepare 0.20 dm3 of solution. What is the
concentration of the resulting solution in mol dm–3?
A.
0.01
B.
0.1
C.
0.2
D.
1.0
(Total 1 mark)
3.
How many molecules are present in a drop of ethanol, C2H5OH, of mass 2.3 × 10–3 g?
(L = 6.0 × 1023 mol–1)
A.
3.0 × 10 19
B.
3.0 × 1020
C.
6.0 × 1020
D.
6.0 × 1026
(Total 1 mark)
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4.
Ethanol is used as a component in fuel for some vehicles. One fuel mixture contains 10 % by
mass of ethanol in unleaded petrol (gasoline). This mixture is often referred to as Gasohol E10.
(a)
Assume that the other 90 % by mass of Gasohol E10 is octane. 1.00 kg of this fuel
mixture was burned.
CH3CH2OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)
1
C8H18(l) + 12 O2(g) → 8CO2(g) + 9H2O(l)
2
(i)
∆HO = –1367 kJ mol–1
∆HO = –5470 kJ mol–1
Calculate the mass, in g, of ethanol and octane in 1.00 kg of the fuel mixture.
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(1)
(ii)
Calculate the amount, in mol, of ethanol and octane in 1.00 kg of the fuel mixture.
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(1)
(iii)
Calculate the total amount of energy, in kJ, released when 1.00 kg of the fuel
mixture is completely burned.
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(3)
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(b)
If the fuel blend was vaporized before combustion, predict whether the amount of energy
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(2)
(Total 7 marks)
5.
What is the total number of hydrogen atoms in 1.0 mol of benzamide, C6H5CONH2?
A.
7
B.
6.0 × 1023
C.
3.0 × 1024
D.
4.2 × 1024
(Total 1 mark)
6.
On analysis, a compound with molar mass 60 g mol–1 was found to contain 12 g of carbon, 2 g
of hydrogen and 16 g of oxygen. What is the molecular formula of the compound?
A.
CH2O
B.
CH4O
C.
C2H4O
D.
C2H4O2
(Total 1 mark)
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7.
Biodiesel makes use of plants’ ability to fix atmospheric carbon by photosynthesis.
Many companies and individuals are now using biodiesel as a fuel in order to reduce their
carbon footprint. Biodiesel can be synthesized from vegetable oil according to the following
reaction.
(a)
Identify the organic functional group present in both vegetable oil and biodiesel.
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(1)
(b)
For part of her extended essay investigation into the efficiency of the process, a student
reacted a pure sample of a vegetable oil (where R = C17H33) with methanol.
The raw data recorded for the reaction is below.
Mass of oil
Mass of methanol
Mass of sodium hydroxide
Mass of biodiesel produced
= 1013.0 g
= 200.0 g
=
3.5 g
= 811.0 g
The relative molecular mass of the oil used by the student is 885.6. Calculate the amount
(in moles) of the oil and the methanol used, and hence the amount (in moles) of excess
methanol.
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(3)
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(c)
The reversible arrows in the equation indicate that the production of biodiesel is an
equilibrium process.
(i)
State what is meant by the term dynamic equilibrium.
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(1)
(ii)
Using the abbreviations [vegetable oil], [methanol], [glycerol] and [biodiesel]
deduce the equilibrium constant expression (Kc) for this reaction.
(1)
(iii)
Suggest a reason why excess methanol is used in this process.
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(1)
(iv)
State and explain the effect that the addition of the sodium hydroxide catalyst will
have on the position of equilibrium.
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(2)
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(d)
The reactants had to be stirred vigorously because they formed two distinct layers in the
reaction vessel. Explain why they form two distinct layers and why stirring increases the
rate of reaction.
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(2)
(e)
Calculate the percentage yield of biodiesel obtained in this process.
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(2)
(f)
When biodiesel is combusted it produces carbon dioxide. Explain why the use of
biodiesel as a fuel does not significantly contribute to global warming.
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(1)
(Total 14 marks)
8.
Which property generally decreases across period 3?
A.
Atomic number
B.
Electronegativity
C.
D.
First ionization energy
(Total 1 mark)
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9.
Which property increases down group 1?
A.
First ionization energy
B.
Melting point
C.
Reactivity
D.
Electronegativity
(Total 1 mark)
10.
(i)
Define the term first ionization energy.
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(2)
(ii)
Explain why the first ionization energy of magnesium is higher than that of sodium.
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(2)
(Total 4 marks)
11.
(a)
State a balanced equation for the reaction of sodium with water. Include state symbols.
(2)
(b)
With reference to electronic arrangements, suggest why the reaction between rubidium
and water is more vigorous than that between sodium and water.
(2)
(Total 4 marks)
12.
Consider the bonding and structure of the period 3 elements.
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(a)
Explain the increase in the melting point from sodium to aluminium.
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(2)
(b)
Explain why sulfur, S8, has a higher melting point than phosphorus, P4.
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(2)
(c)
Explain why silicon has the highest melting point and argon has the lowest melting point.
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(2)
(Total 6 marks)
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13.
Which statements about the periodic table are correct?
I.
The elements Mg, Ca and Sr have similar chemical properties.
II.
Elements in the same period have the same number of main energy levels.
III.
The oxides of Na, Mg and P are basic.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
14.
Some of the most important processes in chemistry involve acid-base reactions.
(a)
Describe the acid-base character of the oxides of each of the period 3 elements, Na to Cl.
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(3)
(b)
State one example of an acidic gas, produced by an industrial process or the internal
combustion engine, which can cause large-scale pollution to lakes and forests.
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(1)
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(c)
Suggest one method, other than measuring pH, which could be used to distinguish
between solutions of a strong acid and a weak acid of the same molar concentration.
State the expected results.
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(2)
(Total 6 marks)
15.
Which series is arranged in order of increasing radius?
A.
Ca2+ < Cl– < K+
B.
K+ < Ca2+ < Cl–
C.
Ca2+ < K+ < Cl–
D.
Cl– < K+ < Ca2+
(Total 1 mark)
16.
Silicon has three stable isotopes, 28Si, 29Si and 30Si. The heaviest isotope, 30Si, has a percentage
abundance of 3.1 %. Calculate the percentage abundance of the lightest isotope to one decimal
place.
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(Total 2 marks)
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17.
Which statement about the numbers of protons, electrons and neutrons in an atom is always
correct?
A.
The number of neutrons minus the number of electrons is zero.
B.
The number of protons plus the number of neutrons equals the number of electrons.
C.
The number of protons equals the number of electrons.
D.
The number of neutrons equals the number of protons.
(Total 1 mark)
18.
How many electrons does the ion
A.
12
B.
15
C.
16
D.
18
31 3
15 P
contain?
(Total 1 mark)
19.
What is the electron arrangement of the Mg2+ ion?
A.
2,2
B.
2,8
C.
2,8,2
D.
2,8,8
(Total 1 mark)
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20.
Which species have the same number of electrons?
I.
S2–
II.
Cl–
III.
Ne
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
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12
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