PAPER 2
JUNE 2015 /
EXAMINER: PW
MODERATOR: AS150 marks/3 hours
BISHOPS
INSTRUCTIONS and NOTES:- This question paper consists of FIVE questions. Answer ALL the questions on lined paper.
- Write your name and your teacher’s initials on each page.
- Both sides of the paper may be used. Start each question on a new page.
- Graph paper will be supplied for Question 3.2.5
- Number the answers correctly according to the numbering system used in this question paper.
- Leave ONE line between two subquestions, for example between 2.1 and 2.2.
- You may use a non-programmable calculator.
- You are advised to use the attached DATA SHEETS.
- Show formulae and substitutions in calculations.
- Round off your final numerical answers to a minimum of TWO decimal places
- Write neatly and legibly.
QUESTION 1
Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. Write only the letter (A–D) next to the question number (1.1–1.10) on your lined paper.
1.1The following molecules all have similar molecular masses. Which compound will have the highest boiling point?
- CH3CH2CH2CH2CH3 B. Cl2 C. CH2CHCH2CH2CH3 D. CH3CH2CH2CH2CHO
1.2Which of the following is NOT a characteristic of an activated complex?
- It is a mixture of reactants and products.
- It is a high energy group of bonded atoms.
- It can break down into reactants or products.
- It is unstable and readily breaks down.
1.3What is the oxidising agent in the following reaction?
2FeF2 + F2 2FeF3
- FeF2 B. F2 C. FeF3 D. There is no oxidizing agent.
1.4Which of the following actions would have a negative impact on the accuracy of an acid-base titration in which the acid was run out of the burette?
- Rinsing the burette with acid only.
- Rinsing the conical flask with distilled water before adding the alkali.
- Rinsing the pipette with distilled water before filling it with alkali.
- Rinsing the funnel with acid before using it to fill the burette.
1.5A 4 mol.dm-3 solution of a monoprotic acid had a pH of exactly 4. Which statement is true about this acid?
A.It is a weak acid.
B.It has a high Ka value.
C.There are no hydroxide ions in the solution.
D.The concentration of oxonium ions in the solution is 4 mol.dm-3.
1.6A heterogeneous catalyst can be described as:
A.one which is in the same phase as the reactants and raises the activation energy.
B.one which is in the same phase as the reactants and lowers the activation energy.
C.one which is in a different phase to the reactants and raises the activation energy.
D.one which is in a different phase to the reactants and lowers the activation energy.
1.7The graphs below represent the change in the rate of reaction versus time for the reversible reaction that took place when an amount of hydrogen (H2) gas and iodine (I2) gas was sealed off in a container. (The broken line represents the reverse reaction.)
H2 (g) / + / I2 (g) / / 2HI(g) / H < 0
The possible changes that occurred at 10 minutes and 15 minutes would be…
At 10 minutes / At 15 minutesA / Catalyst added / P decreased by increasing V
B / P increased by decreasing V / T decreased
C / T increased / H2 extracted
D / P increased by decreasing V / T increased
1.8When a chemical system is in equilibrium and a change in the conditions causes an increase in the value of Kc then the following always happens:
A.The rate of the forward reaction increases only.
B.The rate of the reverse reaction increases only.
C.The rate of both forward and reverse reactions increases.
D.The yield of products increases.
1.9Which ratio of elements below could be a saturated straight chain alcohol?
A.C4H8O B. C4H9O C. C4H10O D. C4H11O2
1.10Which of the following is an example of an elimination reaction?
A.The reaction of a carboxylic acid with an alcohol to form an ester.
B.The reaction between an alkene and water to form an alcohol.
C.The reaction decomposition of alcohol into water and an alkene.
D.The reaction of an alkane with a halogen to form a haloalkane.
{20 marks}
QUESTION 2
2.1A chemist wanted to determine the metal (X) of a hydrated sulphate salt with the formula: XSO4.5H2O. He carefully weighed out 8,55 g of the solid. He heated this gently and the mass dropped to a steady 5,15 g as the water was driven off.
2.1.1How many moles of water were driven off?(4)
2.1.2Calculate the atomic mass of element X.(4)
2.1.3Name the element X.(1)
[9]
2.2Calculate the percentage purity of a sample of iron(III) carbonate if 15,0 g of the impuresample produced 5,71 x 10-2molof carbon dioxide when reacted with excesshydrochloric acid.
Fe2(CO3)3 + 6HCl 2FeCl3 + 3H2O + 3CO2
(The molecular mass of Fe2(CO3)3 is 292.)(5)
[5]
2.3
2.3.1Define an acid according to Lowry-Brønsted.(1)
2.3.2What is the conjugate base of the HCO3- ion?(1)
2.3.3Is ammonia a weak base?(1)
2.3.4Name the two substances formed when calcium oxide reacts with nitric acid.(2)
2.3.5Will the pH of a solution of sodium ethanoate be MORE THAN, LESS THAN OR EQUAL TO seven? (1)
2.3.6Calculate the pH of a 0,44 mol.dm3 solution of sulphuric acid.(4)
[10]
2.4An acid-base titration is performed to find the concentration of a solution of oxalic acid using a standard solution of sodium hydroxide. An indicator is used to determine the end point.
2.4.1Define a “standard solution”.(2)
2.4.2Name a suitable indicator for this titration.(1)
2.4.3What colour is this indicator in alkali?(1)
2.4.4What ion is the predominant ion in all alkali solutions?(1)
[5]
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QUESTION 3
3.1White phosphorus burns in air to produce a mixture of two oxides. It is a spontaneous reaction on a warm day.
Reaction 1: P4 + 3O2 P4O6
Reaction 2: P4 + 5O2 P4O10
3.1.1What is the oxidation number of the phosphorus in P4O6?(1)
3.1.2What is the empirical formula of the second oxide?(1)
3.1.3What does “spontaneous” mean in this context?(2)
3.1.4Do these reactions have high or low activation energies?(1)
3.1.5Draw an energy diagram (potential energy versus course of reaction) for the first reaction, using labelled single-headed arrows show the activation energy (EA) and enthalpy change (∆H). Put the formulae of reactants and product into the diagram. (5)
3.1.6Red phosphorus does not ignite spontaneously. Therefore it has a ….(a)….. activation energy and a …(b)…. P-P bond energy than white phosphorus. (2)
3.1.7Calculate ∆H for the second reaction using the information provided below.(5)
P4 / P4O10 / Bond energykJ.mol-1
/ / P-P
O-O
O=O
O-P
O=P / 200
204
498
351
544
[17]
3.2A chemist used the reaction between hexane and bromine to study the rate of a reaction over a period of time. He made use of a spectrometer to record the ratio of the incident light (Io) to transmitted light (I) for a frequency of light which bromine (Br2) absorbs. This ratio can be related to the concentration of bromine present as the reaction proceeds.
1,55 g of bromine was added to hexane and the mixture stirred vigorously to dissolve all the bromine forming 100 cm3 of solution . The mixture was then placed in the spectrometer and after an initial reading further readings were taken every 2 minutes. The results are recorded below.
Time (min) / 0 / 2 / 4 / 6 / 8 / 10 / 12 / 14 / 16/ 0,10 / 0,58 / 0,71 / 0,84 / 0,89 / 0,92 / 0,93 / 0,94 / 0,94
3.2.1What is the independent variable in this experiment?(1)
3.2.2Calculate the concentration of the bromine solution at the start of the reaction.(4)
3.2.3State one fixed variable for this experiment.(1)
3.2.4Why does the I/Io ratio increase as the reaction proceeds?(2)
3.2.5Use the graph paper provided to plot these results.(5)
3.2.6On the same piece of graph paper draw a curve which could represent the same reaction done at a higher temperature. Label it “higher T”. (2)
3.2.7What characteristic of the curve at any point indicates the rate of reaction?(1)
[16]
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QUESTION 4
4.1Some fluorine and hydrogen were placed in a closed 2,0 dm3 container to set up the following chemical equilibrium at 600oC : F2(g) + H2(g) ⇄ 2HF(g)
4.1.1What does chemical equilibrium mean:
4.1.1.1 in terms of rates of reaction?(1)
4.1.1.2 in terms of macroscopic properties?(1)
4.1.2Write the expression for Kc for the reaction.(1)
It was found that when equilibrium was reached the number of moles of each chemical present was:
chemical / F2 / H2 / HFmoles / 0,84 / 0,14 / 4,10
4.1.3Show that the value of Kc is 143(4)
4.1.4Somehydrogen was then pumped into the 2 dm3 container to increase the number of moles of hydrogen to a total value Y. Once a new equilibrium had been reached it was found that the amount of HF present was 4,18 mol. Using the value of Kc given in 4.1.3 calculate the number of moles of hydrogen added to the reaction mixture. (7)
4.1.5What single change would change the value of KC for this reaction?(1)
[15]
4.2The following chemical equilibrium was set up in a closed container by adding equal quantities of carbon monoxide and nitrogen(II) oxide and leaving for several hours.
2CO + 2NO ⇄ 2CO2 + N2 ∆H = - 200 kJ (all gases)
The conditions were then varied causing changes to the system. Complete the table below using INCREASE, DECREASE or NO CHANGE.
Change imposed / Immediate rate of forward reaction / Final moles of N2pressure increase by decreasing the volume / 4.2.1 / 4.2.2
catalyst added / 4.2.3 / 4.2.4
Carbon dioxide added at constant volume. / 4.2.5 / 4.2.6
(6)
4.2.7State le Chatelier’s principle.(2)
4.2.8Explain your answer to 4.2.5 using the word “collisions”.(2)
4.2.9Explain your answer to 4.2.2 in terms of le Chatelier’s principle.(3)
[13]
4.3The Contact process is used to make sulphuric acid. It was named the Contact process because the reacting gases in one of the steps came into “contact” with the catalyst and then reacted. Sulphuric acid has a variety of uses and millions of tonnes are produced every year. When dissolved in water it forms a strong acid.
4.3.1Write a balanced chemical equation for the reversible reaction which happens on the catalyst.(2)
4.3.2What is the name of the compound H2S2O7?(1)
4.3.3Name the salt formed when ammonia reacts with sulphuric acid.(2)
Ammonia is formed in the Haber Process for which the chemical equation is:
N2 + 3H2 ⇄ 2NH3 ∆H < 0
4.3.4Explain whether a high or low temperature would give the highest yield and why a temperature of 450 oC is used in some industrial plants. (3)
[8]
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QUESTION 5
5.1Alkanes, alkenes and alkynes are all hydrocarbons. The main sources of hydrocarbons are natural gas and crude oil.
5.1.1Name the type of intermolecular force that makes hexane a liquid at 20 oC.(1)
5.1.2Define an isomer.(2)
5.1.3Name the following compounds:
5.1.3.1 CH3CH(CH3)CH2CH2CH3(2)
5.1.3.2
5.1.4Draw the structural formula of another branched isomer of the compound in question 5.1.3.1. (2)
5.1.5Write a chemical equation for the complete combustion of ethyne using molecular formulae.(3)
5.1.6Write a chemical equation, using structural formulae for organic molecules, for the reaction between hydrogen chloride (HCl) andbut-1-ene. (2)
5.1.7Name the type of reaction in 5.1.6.(1)
5.1.8The reaction conditions specifically mention a compound which must not be present when hydrogen chloride reacts with but-1-ene. What is the compound? (1)
[17]
5.2Ethanol is naturally produced by the process of fermentation but it can also be produced synthetically from an alkene. It has many uses apart from being used in alcoholic drinks such as wine.
5.2.1Write the structural formula of ethanol.(2)
5.2.2Ethanol boils at +78 oC whereas dimethyl ether (shown below) boils at -24 oC. Explain clearly why there is this large difference by naming and contrasting the intermolecular forces involved. (3)
5.2.3Ethanol is a primary alcohol. NAME a secondary alcohol with five carbons.(2)
5.2.4Name the reagents needed to convert ethanol to chloroethane.(2)
[9]
5.3.1Esters are useful compounds. Their volatility and fragrances mean that they are used in glues and in some sweets and other food stuffs. They are usually made by reacting a carboxylic acid with an alcohol in the presence of a catalyst.Draw the structure of the ester formed when methanoic acid reacts with butan-1-ol. (2)
5.3.2Name the ester.(2)
[4]
5.4To which homologous series do the following compounds belong?
5.4.1 CH3CH2COCH2CH3(1)
5.4.2CH3CH2CCCH2CH3(1)
[2]
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TOTAL 150 MARKS
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