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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: asa.hoshi on November 15, 2007, 11:59:13 am
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CHEMISTRY
Written examination 2
Thursday 15 November 2007
SECTION A - Multiple-choice question
Question 1
IN which one of the following compounds does the transition metal display the lowest oxidation state?
A. CrO3
B. Cu2S
C. MnCl2
D. K2Cr2O7
Question 2
Consider the following nuclear reaction that takes place in stars.
8\4Be + 4\2He --> 12\6C
Which of the following statements about this change is/are correct?
I. The reaction is endothermic
II. The mass of the 12\6 nucleus is greater than the combined masses of the reactants.
A. I only
B. II only
C. both I and II
D. neither I nor II
Question 3
Some information about the element rhenium (Re) is given in the table below.
Isotope Relative isotopic mass
185Re 185.0
187Re 187.0
Given that the relative atomic mass of Re is 186.2, the percentage abundance of 187Re is closest to
A. 40
B. 50
C. 60
D. 70
Question 4
A solution prepared by stirring Na2O(s) in water undergoes an acid-base reaction with a solution prepared from SO3(g) and water.
Which one of the following salts could be isolated from the reaction mixture?
A. Na2S
B. NaHSO3
C. Na2SO3
D. Na2SO4
Question 5
Which one of the following alternatives contains molecules and ions that are all likely to form a complex ion with a transition metal cation.
A. Cl-, F-, CN-, H+
B. NH3, Cl-, F-, H20
C. Na+, CN-, F-, H20
D. CH4, Cl-, NH3, H20
Question 6
Predict which one of the following compounds would be coloured.
A. BaSO4
B. AlPO4
C. KClO4
D. NaMnO4
Question 7
Which of the following statements about enzymes are correct?
I. Enzymes are proteins.
II. Enzymes increase the rate of biochemical reactions.
III. Enzymes increase the equilibrium constant of biochemical reactions.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
Question 8
A structure of Vitamin C is given below:
Vitamin C is an important biological molecule. It is often added to foods as an antioxidant. Based on this information, and on the structure of Vitamin C shown above, it can be predicted that vitamin C is more soluble in
A. fats than in water and is a good oxidant
B. fats than in water and is a good reductant
C. water than in fats and is a good oxidant
D. water than in fats and is a good reductant
Question 9
The types of compounds that comprised the major food groups include carbohydrates, fats and proteins. A sample, containing only one of these three types of compounds, is analyzed and found to contain the following
Carbon: 76.2%
Oxygen: 11.3%
Nitrogen: 0%
The compound
A. is likely to be a fat
B. is likely to be a protein
C. is likely to be a carbohydrate
D. cannot be identified as the percentage composition of other elements has not been given.
Question 10
The follow two unbalanced equations represent process which are part of the nitrogen cycle.
I. NH3 (aq) --> NH4+ (aq)
II. NH4+ (aq) --> NO3-(aq)
Which one of the following alternatives correctly describes the reactants in each of these processes?
In process I, NH3(aq) is... In process II, the NH4+(aq) ion is
A. an acid...reduced
B. a base...reduced
C. an acid...oxidised
D. a base...oxidised
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Thanks asa.hoshi :wink: Now lets wait for Coblin's answers :D
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Question 11
Consider the following half cells which are set up under standard conditions.
Half Cell - electrode - electrolyte
I - metal A - A2+ (aq)
II - platinum - B2+(aq) and B3+ (aq)
III - metal C - C+ (aq)
-> When a galvanic cell is constructed from half cell I and half cell II, the electrode in half cell II is negative.
-> When a galvanic cell is constructed from half cell II and half cell III, the electrode in half cell III is negative.
The strongest oxidant is
A. A2+ (aq)
B. B2+(aq)
C. B3+ (aq)
D. C+ (aq)
Questions 12, 13, 14 refer to the following information.
The diagram below represents a diaphragm cell used for the commercial production of chlorine gas.
at the +ve section - brine is inserted and X comes out
at the -ve section - Y and sodium hydroxide solutions comes out
middle - porous diaphragm
Question 12
The gases labelled X and Y are
X...Y
A. chlorine... oxygen
B. oxygen...chlorine
C. chlorine...hydrogen
D. hydrogen...chlorine
Question 13
On function of the porous diaphragm in the cell is to
A. act as a catalyst to increase the rate of reaction
B. allow movement of ions between the cell compartments
C. prevent sodium ions from entering the solution near the anode
D. prevent the electrolyte from making contact with the gases produced.
Question 14
A highly concentrated salt solution, called brine, is used as the electrolyte in this cell.
The main reason that a highly concentrated, rather than a diluted, solution is used is in order to
A. allow an electric current to pass through the cell.
B. produce chlorine gas, in preference to oxygen gas.
C. allow sodium hydroxide to be separated from the salt by crystallization.
D. create non-standard conditions that ensure hydrogen gas production.
A rechargeable cell, used in laptop computers, contains a metal alloy (designated M) which has hydrogen atoms adsorbed on its surface, and nickel in the form of NiO(OH)(s) and Ni(OH)2(s),
The half reactions, written as reduction reactions, are
H2O(l) + e- <--> H (adsorbed on M) +OH-(aq)
NiO(OH)(s) + H2O(l) + e- <--> Ni(OH)2(s) + OH-(aq)
Question 15
When this cell is generating electricity
A. NiO(OH) acts as the oxidant
B. the concentration of OH-ions in the cell increases as the cell discharges
C. OH- ions produced at the negative electrode migrate to the positive electrode.
D. electrons flow in the external circuit from the positive to the negative electrode.
Question 16
When the cell is recharged, which one of the following precesses occurs at the electrode connected to the positive terminal of the external power source?
A. reduction of H2O(l)
B. reduction of NiO(OH)(s)
C. oxidation of Ni(OH)2(s)
D. oxidation of H (adsorbed on M)
Question 17
A fuel cell currently under development for powering small electronic devices is based on the reaction of methanol and oxygen using an acidic electrolyte.
The reductant in the cell reaction and the half reaction at the anode are
reductant...anode reaction
A. methanol... O2(g) + 4H+(aq) v+ 4e- --> 2H2O(l)
B. oxygen... O2(g) + 4H+(aq) v+ 4e- --> 2H2O(l)
C. methanol... CH3OH(g) + H2O(l) --> CO2(g) + 6H+(aq) + 6e-
D. oxygen... CH3OH(g) + H2O(l) --> CO2(g) + 6H+(aq) + 6e-
Questions 18, 19 refer to the following information.
A chemist used bomb calorimetry to measure the enthalpy change (delta H) for the combustion of butane.
Question 18
The calibration factor (CF) of the calorimeter was determined by measuring the temperature rise (delta T1) that occurred when a known amount of charge (Q) was passed through the heating element in the calorimeter at a measured voltage (V).
The CF in JC-1 is
A. Q/[V x delta T1]
B. delta T1/[Q x V]
C. Q x V x delta T1
D. [VxQ]/[delta T1]
Question 19
In the calorimeter (calibration factor, CF), n mol of butane was then burnt and the resulting temperature rise (delta T2) was measured.
The deltaH, in Jmol-1, for the reaction
2C4H10(g) + 13O2(g) --> 8CO(g) + 10H2O(l)
is
A. 2 x CF x deltaT2 x n
B. [2 x CF x deltaT2] / n
C. [CF x deltaT2] / [2 x n]
D. [CF x deltaT2] / [n]
Question 20
During the production of electricity in a coal-fired power station, energy is present in the following forms.
I. mechanical energy of turbine.
II. chemical energy of coal and oxygen.
III. thermal energy of steam.
The amount of energy in each of these forms that take part in the generation of a fixed quantity of electricity is, from lowest to highest
A. III, I, II
B. I, II, III
C. I, III, II
D. II, III, I
END OF SECTION A
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SECTION B - Short answer questions
Question 1
Refer to the periodic table in the data sheet when answering this question.
Identify each of the following elements on the basis of the properties listed in the table below. Write its chemical symbol in the appropriate box in the third column.
Property...chemical symbol of the element
i. The element which forms an ion with electron configuration if 1s 2s2 2p6 and a charge of 2+
ii. The third member of the actinides
iii. A period 3 element which forms an ionic oxide that reacts with both acids and bases.
iv. In the ground state, atoms of this element have electrons in 2 shells and the first four ionization energies are 0.80, 2.43, 3.66 and 25.02 MJ mol-1
v. A element that is more electronegative that chlorine and its atoms have an outer-shell configuration of s2p4
vi. An element which is more metallic that germanium (Z=32), has a higher first ionization energy than bismuth (Z=83) and atoms with an outer-shell configuration of s2p2.
Total 6 marks
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SECTION B - Short answer questions
Question 2
The work of many scientists has contributed to an understanding of atomic structure. As a result of their work, previously unknown elements have been discovered and the search for new elements continues today.
a. Dimitri Mendeleev (1834-1907) is usually given much of the credit for systematically arranging the elements into a periodic table. Briefly describe two important features of the table he created.
2 marks
b. The discovery of element 113 was claimed by teams of Russian and American scientists in February 2004. Following international conventions, it has initially been given the name ununtrium and the symbol Uut, before a permanent name and symbol are given to it.
Uut undergoes rapid radioactive decay but atoms of Uut have been identified with a mass number of 283 and also with a mass number of 284.
i. Name an instrument that could be used to determine the mass numbers of different isotopes of an element.
ii. State the number of subatomic particles in an uncharged Uut atom of mass number 284.
Protons:___ Electrons:___ Neutrons:___
iii. In what group and period is Uut located in the periodic table?
Group:___ Period:___
iv. Given the symbol of the element that is expected to be most similar to Uut in chemical properties.
v. In terms of atomic structure, explain why the atomic radius of Uut is predicted to be smaller than that of Fr (Z=87).
vi. In terms of atomic structure, explain why the the first ionisation energy of Uut is predicted to be smaller than that of Al (Z=13).
vii. Atoms of Uut with a mass number of 283 undergo radioactive decay into two particles, one of which is an alpha-particle (a helium nucleus). Write a balanced equation for this nuclear reaction.
1 + 1 + 2 + 1 + 1 + 1 + 1 = 8 marks
Total 10 marks
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SECTION B - Short answer questions
Question 3
The arrangements of electrons in atoms and ions are often written in simplified form, known as 'condensed electron configuration'. For example,. the condensed electron configuration of beryllium is written as
[He]2s2
where [He[ stands for the electron configuration of helium (1s2), which is the noble gas element previous to beryllium in the periodic table.
a. Write condensed electron configuration for the following atoms and ions.
i. C
ii. Fe
iii. Fe2+
1 + 1 + 1 = 3 marks
b. State the group and period of the periodic table where an element with the electron configuration [Kr]4d10 5s2 5p4 is found.
Group:___ Period:___
1 mark
Total 4 marks
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much appreciated asa :D
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SECTION B - Short answer questions
Question 8
Faraday's constant is defined as the charge on one mole of electrons. The value of Faraday's constant can be determined experimentally by electrolysis using inert electrodes.
A current of 1.62 A is passed through a solution of copper (II) nitrate for 581 s. At the end of that time, the copper deposited at the negative electrode was collected. Its mass was found to be 0.306g.
a. Write an equation for the half reaction occurring at the negative electrode of this electrolytic cell.
1 mark
b. Use the experimental data given above to calculate, to an appropriate number of significant figures, the
-> charge, in coulombs, that was passed through the electrolytic cell
-> amount, in mol, of copper deposited at the negative electrode.
3 marks
c. Use the values obtained in part b. to calculate the experimentally determined value of Faraday's constant.
d. The value of Faraday's constant given in your data sheet is 96500 C mol-1. The experiment above was repeated and a value for Faraday's constant was found to be 98400 C mol-1. The amount of charge passed is accurately known. Described one possible source of experimental error which would result in obtaining an experimental value that was higher than the one given in the data sheet.
1 mark
Total 7 marks
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ok my hands are tired after 1 hour of typing this crap. I seriously don't care about CHEMISTRY anymore! but i do care about FSN! That's why I spent 1 hour of my time typing this instead of resting.
Anyway, that's all I'm typing for today. I might be able to take photos of it tonight when I get my camera back. Gotta rest and study for exams. Bye!
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SECTION B - Short answer questions
Question 6
Ethanol (C2H5OH) is a common fuel burnt in some lightweight, compact stoves suitable for use when hiking.
[picture of cooking pot, fuel, stove]
a. Consider the following information
-ethanol burns in excess air according to the following equation.
C2H5OH (l) + 3O2 (g) --> 2CO2 (g) + 3H2O(g) DeltaH = -1364 kJ mol-1
-The cooking pot is made from aluminiym and has a mass of 150g.
-The specific heat capacity of aluminum is 0.900 Jg-1C-1.
-The specific heat capacity of water is 4.18 Jg-1C-1.
i. Calculate the minimum amount of energy, in kJ, required to heat 550g of water and the pt from 18.5C to 100.0C
iiCalculate the mass, in g, of ethanol that needs to be completely burnt to provide this energy.
iii Only 35% of the energy released by the combustion of ethanol is transferred to the cooking pot and contents. Calculate the mass, in g, of ethanol that needs to be burnt in practice to heat the water and pot from 18.5C to 100.0C.
2 + 2 + 1 = 5 marks
b. Other camping stoves use butane (C4H10) as fuel. Given that, on complete combustion, 6.00g of butane releases the same amount as 10.0g of ethanol, calculate the magnitude of deltaH, in kJ mol-1, for the reaction
2C4H10 (g) + 13O2 (g) --> 8CO(g) + 10H2O (g)
2 marks
Total 7 marks
NO more typing... lol
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Asa.hoshi, you GOD.
Good job!! FSN appluads your dedication. Better rest those wrists... you do have more exams, right? :P
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Top work asa.
Quality.
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Thanks heaps asa.
I've been fixing your errors. Can someone check Question 4. I think I've fixed it, but I may have option C incorrect (because I haven't seen the question).
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Asa.hoshi, you GOD.
Good job!! FSN appluads your dedication. Better rest those wrists... you do have more exams, right? :P
got 2 big ones left. spesh and jap
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Good luck for those. No doubt coblin wants a piece of Spesh.
By the way, coblin, it doesn't matter what option C was, because it's incorrect regardless. :P
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SECTION A - Multiple-choice questions
Question 1
CrO3 => +6
Cu2S => +1 (The sulfide ion is -2)
MnCl2 => +2
K2Cr2O7 => +6
The answer is B.
Question 2
The reaction is a fusion reaction involving species smaller than iron-56, so: I. "The reaction is endothermic" is incorrect.
Energy is released, and according to E=mc^2, mass is lost to compensate for the release in energy, so: II. "The mass of the carbon-12 nucleus is greater than the combined masses of the reactants" is incorrect.
The answer is D.
Question 3
Let a be the proportion of rhenium-187:
185(1-a) + 187a = 186.2
=> 2a = 1.2
=> a = 0.6 = 60%
The answer is C.
Question 4
SO3(g) + H2O(l) --> H2SO4(aq)
The salt will be Na2SO4, while the oxide ion and protons have fun neutralising each other.
The answer is D.
Question 5
Ligands must have a spare electron pair, or be negatively charged, to be attracted to the central metal cation:
Set A contains H+: incorrect
Set B appears correct
Set C contains Na+: incorrect
Set D contains CH4: incorrect (no free electron pair, all are participating in C-H bonds)
The answer is B.
Question 6
Transition metal compounds tend to exhibit colour: barium, aluminium, potassium and sodium are not transition metals, but manganese (Mn) is.
The answer is D.
Question 7
Enzymes are class of proteins that are known for their catalytic ability in biological reactions. Statements I and II are correct. III is incorrect, a catalyst does not affect the equilibrium constant at all.
The answer is A.
Question 8
Antioxidants sacrifically oxidise in reaction with oxidants in defence of foods that would otherwise become rancid. In order to sacrificially oxidise, it must be a good reductant. (answer B or D)
A key feature of antioxidants is the number of OH groups they possess, so antioxidants are also soluble in water.
The answer is D.
Question 9
The compound is not a protein, because there is no nitrogen. This means it is a carbohydrate or fat, which consist of hydrogen only:
=> Hydrogen: 100 - 76.2 - 11.3 = 12.5%
n(C) : n(H) : n(O) = 76.2/12 : 12.5/1 : 11.3/16
= 6.35 : 12.5 : 0.706
= 9 : 18 : 1
It is most likely a fat of the molecular formula: C18H36O2. Carbohydrates have a much higher oxygen content.
The answer is A.
Question 10
In process I, NH3 accepts a proton, it acts as a base.
In process II, NH4+ is oxidised from an oxidation state of -3 to +5.
The answer is D.
Question 11
(+) Half cell I | Half cell II (-) => B2+ is oxidising while A2+ is reducing
(+) Half cell II | Half cell III (-) => C is oxidising while B3+ is reducing
While B3+ is a stronger oxidant than C+, A2+ is a stronger oxidant than B3+ (reduces more readily). Therefore A2+ would be a stronger oxidant than C+ too.
The answer is A.
Question 12
The positive section is the anode, where the oxidation of Cl- occurs. X is chlorine.
The negative section is the cathode, where the reduction of H2O occurs. Y is hydrogen (see electrochemical series).
The answer is C.
Question 13
The porous diaphgram allows the movement of ions (Na+ particularly) so that NaOH can be formed.
The answer is B.
Question 14
The highly concentrated salt solution exceeds the standard conditions of 1M, thus creating non-standard conditions that cause the order of the chlorine and water reaction to swap, allowing chlorine to be produced in preference to oxygen gas.
The answer is B.
Question 15
While generating electricity, M acts as the anode. Therefore, a reduction is occurring in the nickel half-cell, with NiO(OH) being reduced, thus acting as an oxidant.
The answer is A.
Question 16
While being recharged, the positive terminal is the anode where oxidation occurs. In the forward reaction, NiO(OH) acts as the oxidant and is reduced to Ni(OH)2. Therefore in the reverse reaction, Ni(OH)2 must be oxidised instead.
The answer is C.
Question 17
The answer must be C or D, as they are the only options that show oxidation reactions at the anode.
The reductant is methanol, as it becomes oxidised at the anode (as suggested by options C or D, and by commonsense that oxygen is an oxidant).
The answer is C.
Question 18
The calibration factor = energy input / change in temperature. Energy input is Q*V, while the change in temperature is ∆T1. (Typically, we use E = VIt, but since Q = It, we can say E = V*Q)
The answer is D.
Question 19
∆H = - (CF * ∆T2) * 2/n
The factor (2/n) was to adjust the energy output (CF * ∆T2) into per mol. There are 2 moles of butane per mole of reaction, and n moles of butane was combusted, so this is a compensation factor.
VCAA forgot the negative sign!
The answer is B.
Question 20
For a fixed amount of electrical output, we would require the highest amount of chemical energy in coal and oxygen, as this is the first step in the process, and a lot of the energy is lost as heat.
The key is identifying which steps are the earliest in the power production process. The generation of steam occurs next, and there will be more energy in the steam then there will be from the turbine spinning, because not all of the thermal energy of steam will be transferred to the turbine. (I < III < II)
The answer is C.
Since this is the last MC question, I'll digress: this question takes a while to digest. Here's an alternative, more risky route for those who couldn't comprehend it. From an earlier post:
Heh, answer is C without even reading the question. Options A and C indicate II is certainly the last one. Options B and C indicate I is certainly the first one. C is the intersection. (edit: you can even reinforce this further by using this reasoning on the middle one, it's certainly III by options C and D, C is the ultimate intersection!)
An illustrative example (this is a fitting final MC, because it is confusing):
Suppose there is a 1000 units of chemical energy. 400 units of this becomes thermal energy, while 600 units is lost as heat. Then, 300 units of the remaining 400 units is converted into the mechanical energy of the turbine. 100 units must be lost from heat. We are producing a fixed amount of electricity (300 units), where the required units of input vary (the earlier steps require more input to compensate for the certain loss of energy from heat).
END OF SECTION A
...beginning of dinner, be back soon.
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damn three wrong for me...things looking not so good....just waiting for section B now..crickey!
thanks coblin
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nice work typing it up :P although i'll try to avoid the answers ...i don't want to get depress cause i still got 1 more exam left 2 do :/
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SECTION B - Short answer questions
Question 1
i. Mg
ii. U
iii. Al
iv. B
v. O
vi. Sn
Question 2
a)
Any two of these three features:
- Elements with similar chemical properties were placed in the same "group."
- There were spaces where Mendeleev predicted "missing elements."
- The table was ordered by increasing atomic mass.
b)
i. Mass spectrometer
ii. Protons: 113, Electrons: 113, Neutrons: 171
iii. Group: III, Period 7
iv. Tl
v. Fr is in group I, so it has a weaker nuclear core charge than Uut, which means the electrons in Uut are more tightly bound to the nucleus, hence the atomic radius of Uut is smaller than Fr.
vi. Al is in period 3 and since it has the same nuclear core charge as Uut, it has a stronger attraction on the fewer number of electrons it has compared to the electrons on Uut, hence electrons on Uut are easier to ionise.
vii.
283 4 279
Uut ---> He + Rg
113 2 111
Question 3
a)
i. [He]2s22p2
ii. [Ar]3d64s2
iii. [Ar]3d6
(These should be superscript instead)
b)
Group: VI, Period 5
Question 4
a)
i. C6H12O6
ii. C12H22O11 + 12O2 ---> 12CO2 + 11H2O
iii. ΔH = -2816*2 = -5632 kJ/mol. 1 mole of maltose can hydrolyse into 2 moles of glucose.
b)
i. C15H29COOH => 30 hydrogen atoms
ii. H
|
H-C-O-H
|
H-C-O-H
|
H-C-O-H
|
H
c)
i. CH3OH + C17H35COOH ---> H2O + C17H35COOCH3
ii. C17H35[COO]CH3 (in square brackets)
d)
Lecithin has a non-polar half, and polar half, which allows lecithin to interact with both water and oil, and can create oil in water suspensions, and vice versa.
Question 5
a)
i.
CH3
|
H2N-C-COOH
|
H
ii.
H
|
HO-C=O
|
H-C-H
|
N-H
|
O=C
|
H-C-CH3
|
NH2
b)
i. Circle any one of the many:
|
N-H
|
O=C
|
ii. Z2 (-CH2CH2CH2CH2NH2)
iii. Z1 (-CH2SH)
iv. Enzymes are sensitive to pH and temperature. Under different pH conditions, it's shape can change and it can denature.
v. Urea:
H H
\ /
N
|
C=O
|
N
/ \
H H
Question 6
a)
i. E = (100-18.5)[550*4.18 + 150*0.900] = 198*10^3 J = 198 kJ
ii. n(C2H5OH) = 198/1364 = 0.145 mol
=> m(C2H5OH) = 0.145 * 46.0 = 6.69 g
iii. mass = (1/0.35) * 6.69 = 19.1 g
b)
n(C2H5OH) = 10.0 / 46.0 = 0.217 mol => E = 0.217 * 1364 = 296 kJ
n(C4H10) = 6.00 / 58.0 = 0.103 mol
=> ΔH = -296*2 / 0.103 = -5730 kJ/mol
(2 moles of butane per mole of reaction)
Question 7
a)
i. Platinum
ii. temperature: 25?C, pH = 0
b) Cadmium
An increase in pH indicates H+ has been consumed. This means the forward reaction involves the reduction of H+(aq) into H2(g). Thus, the stronger reductant out of H2(g) and Cd(s) is cadmium.
c)
i. n(X2+) = n(initial) - n(final) = 0.100*(1.00 - 0.725) = 0.0275 mol
ii. Q = 2654 => n(e-) = 2654/96500 = 0.0275 mol
=> n(X2+) = n(e-) = 0.0275 mol
=> n(X2+):n(e-) = 1:1
iii. X3+
iv. X2+ ---> X3+ + e-
Question 8
a)
cathode: Cu2+(aq) + 2e- ---> Cu(s)
b)
Q = 1.62*581 = 941 C
n(Cu) = 0.306/63.6 = 4.81*10^-3 mol
c)
n(e-) = 2*n(Cu) = 9.62*10^-3 mol
=> F = Q/n(e-) = 941 / (9.62*10^-3) = 97800 C/mol
d)
Any of the following:
- Only a fraction of the extra copper was weighed (due to flaking).
- Inefficient cell and/or resistance in wires causing a lower n(e-) than expected.
END OF EXAM
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Interesting. I talked about a systematic error with scales.
The third actinide is Uranium, according to my textbook. So we have some problems.
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6a you missed the energy to heat the aluminium pot
Other then that, thank you ^_^
So pissed off at myself for misreading/interpreting one of the multi choice, especially as I originally wrote the correct answer >_<
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Interesting. I talked about a systematic error with scales.
The third actinide is Uranium, according to my textbook. So we have some problems.
Sorry, I was looking at the Wikipedia periodic table, which is weird (updated).
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6a you missed the energy to heat the aluminium pot
Other then that, thank you ^_^
So pissed off at myself for misreading/interpreting one of the multi choice, especially as I originally wrote the correct answer >_<
Yeah, oops. I misread questions when they're on the computer. :cry:
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I have the full copy of Section B (thanks to asa.hoshi). I will have the full solutions in a bit. I may need to draw and upload.
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I have the full copy of Section B (thanks to asa.hoshi). I will have the full solutions in a bit. I may need to draw and upload.
Thanks coblin :)
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Interesting. I talked about a systematic error with scales.
The third actinide is Uranium, according to my textbook. So we have some problems.
Sorry, I was looking at the Wikipedia periodic table, which is weird (updated).
what the..is it not uranium??? this is very confusing
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farrrk
i just cant stop making bullshit mistakes
6 marks off - 7 maybe at worst
what study score am i looking at with 5 marks off 1st exam
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Interesting. I talked about a systematic error with scales.
The third actinide is Uranium, according to my textbook. So we have some problems.
Sorry, I was looking at the Wikipedia periodic table, which is weird (updated).
what the..is it not uranium??? this is very confusing
actinide series, a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series. The series always includes the 14 elements with atomic numbers 90 through 103. The other members are (in order of increasing atomic number) thorium, protactinium, uranium
(The Columbia Electronic Encyclopedia, 6th ed. Copyright ? 2007, Columbia University Press. All rights reserved.)
Wouldn't that make that question ambiguous? I said Uraninum, but lots of periodic tables I've looked up include actinide in the series!?
AHHHH! RIPPED OFF!
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Interesting. I talked about a systematic error with scales.
The third actinide is Uranium, according to my textbook. So we have some problems.
Sorry, I was looking at the Wikipedia periodic table, which is weird (updated).
what the..is it not uranium??? this is very confusing
actinide series, a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series. The series always includes the 14 elements with atomic numbers 90 through 103. The other members are (in order of increasing atomic number) thorium, protactinium, uranium
(The Columbia Electronic Encyclopedia, 6th ed. Copyright ? 2007, Columbia University Press. All rights reserved.)
Wouldn't that make that question ambiguous? I said Uraninum, but lots of periodic tables I've looked up include actinide in the series!?
AHHHH! RIPPED OFF!
Nah, you'd use the VCAA Periodic Table, where U was the third member. I was looking at the periodic table off Wikipedia, which seems to believe in the other way. My mistake, sorry (obeys VCAA's Chemistry laws... but NEVER their ideas on ligands!)
I'm almost done, was sidetracked from Heroes (what a GOOD episode!)
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Coblin you are my hero :)
Can you send me photos of you so I can put them up around my room and worship you?
No, seriously, thanks so much for doing this.
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Coblin you are my hero :)
Can you send me photos of you so I can put them up around my room and worship you?
No, seriously, thanks so much for doing this.
Don't forget. We have to thank asa.hoshi for the quick supply of the paper. I want to ask though, was there any information omitted from Q15 and 16 of the multi-choice? My reasoning is deductive rather than constructive. I've only eliminated instead of actually figured out the answer.
Thanks asa.hoshi!
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I want to ask though, was there any information omitted from Q15 and 16 of the multi-choice? My reasoning is deductive rather than constructive. I've only eliminated instead of actually figured out the answer.
lol sorry. there is some info. i remember typing it up. but somehow it got deleted. i type it up again. here ya go!
Questions 15 and 16 refer to the following information.
A rechargeable cell, used in laptop computers, contains a metal allow (designated M) which has hydrogen atoms adsorbed on its surface. and nickel in the form of NiO(OH) (s) and Ni(OH)2(s).
The half reactants, written as reduction reactions, are
H2O(l) + e- <--> H (adsorbed on M) + OH-(aq)
NiO(OH)(s) + H2O(l) + e- <--> Ni(OH)2(s) + OH-(aq)
While this cell is generating electricity, the metal alloy acts as the negative electrode.
Question 15
When this cell is generating electricity
A. NiO(OH) acts as the oxidant
B. the concentration of OH-ions in the cell increases as the cell discharges
C. OH- ions produced at the negative electrode migrate to the positive electrode.
D. electrons flow in the external circuit from the positive to the negative electrode.
Question 16
When the cell is recharged, which one of the following precesses occurs at the electrode connected to the positive terminal of the external power source?
A. reduction of H2O(l)
B. reduction of NiO(OH)(s)
C. oxidation of Ni(OH)2(s)
D. oxidation of H (adsorbed on M)
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Alright, cool :D
Thanks again!
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Alright, cool :D
Thanks again!
no probs. its a good way of getting my post-count up. maybe i should of made each multiple choice question 1 post. LOL :lol:
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CHEMISTRY
Written examination 2
Thursday 15 November 2007
SECTION A - Multiple-choice question
Question 1
IN which one of the following compounds does the transition metal display the lowest oxidation state?
A. CrO3
B. Cu2S
C. MnCl2
D. K2Cr2O7
Question 2
Consider the following nuclear reaction that takes place in stars.
8\4Be + 4\2He --> 12\6C
Which of the following statements about this change is/are correct?
I. The reaction is endothermic
II. The mass of the 12\6 nucleus is greater than the combined masses of the reactants.
A. I only
B. II only
C. both I and II
D. neither I nor II
Question 3
Some information about the element rhenium (Re) is given in the table below.
Isotope Relative isotopic mass
185Re 185.0
187Re 187.0
Given that the relative atomic mass of Re is 186.2, the percentage abundance of 187Re is closest to
A. 40
B. 50
C. 60
D. 70
Question 4
A solution prepared by stirring Na2O(s) in water undergoes an acid-base reaction with a solution prepared from SO3(g) and water.
Which one of the following salts could be isolated from the reaction mixture?
A. Na2S
B. NaHSO3
C. Na2SO3
D. Na2SO4
Question 5
Which one of the following alternatives contains molecules and ions that are all likely to form a complex ion with a transition metal cation.
A. Cl-, F-, CN-, H+
B. NH3, Cl-, F-, H20
C. Na+, CN-, F-, H20
D. CH4, Cl-, NH3, H20
Question 6
Predict which one of the following compounds would be coloured.
A. BaSO4
B. AlPO4
C. KClO4
D. NaMnO4
Question 7
Which of the following statements about enzymes are correct?
I. Enzymes are proteins.
II. Enzymes increase the rate of biochemical reactions.
III. Enzymes increase the equilibrium constant of biochemical reactions.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
Question 8
A structure of Vitamin C is given below:
Vitamin C is an important biological molecule. It is often added to foods as an antioxidant. Based on this information, and on the structure of Vitamin C shown above, it can be predicted that vitamin C is more soluble in
A. fats than in water and is a good oxidant
B. fats than in water and is a good reductant
C. water than in fats and is a good oxidant
D. water than in fats and is a good reductant
Question 9
The types of compounds that comprised the major food groups include carbohydrates, fats and proteins. A sample, containing only one of these three types of compounds, is analyzed and found to contain the following
Carbon: 76.2%
Oxygen: 11.3%
Nitrogen: 0%
The compound
A. is likely to be a fat
B. is likely to be a protein
C. is likely to be a carbohydrate
D. cannot be identified as the percentage composition of other elements has not been given.
Question 10
The follow two unbalanced equations represent process which are part of the nitrogen cycle.
I. NH3 (aq) --> NH4+ (aq)
II. NH4+ (aq) --> NO3-(aq)
Which one of the following alternatives correctly describes the reactants in each of these processes?
In process I, NH3(aq) is... In process II, the NH4+(aq) ion is
A. an acid...reduced
B. a base...reduced
C. an acid...oxidised
D. a base...oxidised
Wow. Talk about dedication. It seems from this test that some things I learnt in bio might actually pop up in chem next year.
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kido if you have a whole AOS on food chem bio will without a doubt be handy. i barely had to go over food chem
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It is the opposite way around.
Bio will help me out in chem.
That is the only good thing that could come out of bio, seeing i stuffed Exam 2 up.
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wow asa.hoshi thats so nice of you!