Exam 2017, questions PDF

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Seat Number

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Student Number

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CONFIDENTIAL EXAM PAPER This paper is not to be removed from the exam venue Chemistry

EXAMINATION Semester 1 - Main, 2017

CHEM1102 Chemistry 1B For Examiner Use Only

EXAM WRITING TIME:

2 hours

READING TIME:

10 minutes

Marks Page(s) Max

EXAM CONDITIONS: This is a closed book examination - no material permitted

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MATERIALS PERMITTED IN THE EXAM VENUE: (No electronic aids are permitted e.g. laptops, phones)

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Calculator - non-programmable

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MATERIALS TO BE SUPPLIED TO STUDENTS: none

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During reading time - writing is not permitted at all

INSTRUCTIONS TO STUDENTS: The total score for this paper is 100. The possible score per page is shown in the adjacent table. The paper comprises of 16 pages of short answer questions. ANSWER ALL QUESTIONS. Answer all short answer questions in the spaces provided on this question paper. Credit may not be given where there is insufficient evidence of the working required to obtain the solution. Each new short answer question starts with a •. Take care to write legibly. Write your final answers in ink, not pencil. Numerical values required for any question, standard electrode reduction potentials, a Periodic Table and some useful formulas may be found on the separate data sheet. Please check your examination paper is complete (page numbers in footer of page) and indicate by signing below. I have checked the examination paper and affirm it is complete.

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Student Signature: ______________________________ Date: ______________

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Marker

CHEM1001



Semester 1, 2017

Page 2 of 16

Marks 5

Consider the following reaction:

Identify the nucleophile:

Identify the electrophile:

The final product above is shown without absolute stereochemistry at the carbon labelled with an asterisk (*). Draw the structures of the two potential products indicating absolute stereoconfiguration, and label each structure as either (R) or (S).

Page Total:

CHEM1001

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Semester 1, 2017

Page 3 of 16

Draw structures for the expected intermediate and product in this substitution reaction.

What effect would doubling the concentration of hydroxide (OH) have on the overall reaction rate?

What effect would doubling the concentration of 2-bromo-2-methyl-butane have on the overall reaction rate?

Complete the energy profile diagram for the reaction above. Add labels to indicate any intermediate(s), transition state(s) and the activation energy.

Page Total:

Marks 8

CHEM1001

Semester 1, 2017

Page 4 of 16

Marks 8

Give structures for the products for each of the following reactions.

Draw a complete mechanism showing the final reaction of ethylamine with the acid chloride to produce the final product.

Page Total:

CHEM1001

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Semester 1, 2017

Page 5 of 16

The addition of HBr to alkenes can result in two possible products. Using curly arrows and the template below, draw the mechanism for this reaction to show the formation of products C and D, and the intermediate structures A and B.

Indicate which structure will be the major product, and explain why it will predominate.

Page Total:

Marks 8

CHEM1001

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Semester 1, 2017

Page 6 of 16

The major product of an elimination reaction can be controlled depending on the reagent used. Draw curly arrows to complete mechanisms for each reaction below to form the major product, show any relevant hydrogens.

Name the major product of Reaction 1, unambiguously.

Page Total:

Marks 7

CHEM1001

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Semester 1, 2017

Page 7 of 16

Retinal is the chemical basis for vision in animals, and is closely related to Vitamin A and Retinoic acid:

Identify the functional groups in the dashed boxes labelled P and Q. P:

Q: What chemical reagent could be used to convert Retinal A to Vitamin A?

What chemical reagent could be used to convert Vitamin A to Retinoic Acid?

What type of isomers are Retinal A and Retinal B?

Page Total:

Marks 5

CHEM1001

Semester 1, 2017

Page 8 of 16

Marks 4

Indicate the hybridisation of each atom labelled A through to D: A:

B:

C:

D:

PET (polyethylene terephthalate) is a polyester plastic which could potentially be made from diacyl chloride monomer X and ethylene glycol monomer Y. Draw the repeating polymer unit formed in the reaction of X and Y.

Page Total:

CHEM1001

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Semester 1, 2017

Page 9 of 16

Curly arrows are a useful tool to illustrate flow of electrons and resonance. By considering the conjugate base and with the aid of curly arrows, explain why acetic acid is more acidic than ethanol.

The resonance contributor shown below is not aromatic. Use curly arrows to show movement of electrons to form a resonance contributor that is aromatic.

Page Total:

Marks 5

CHEM1001



Semester 1, 2017

Page 10 of 16

For the reaction below, identify the acid and its type. Give a definition of this acid type. H+ + Cl  HCl AlCl3 + Cl  [AlCl4] Provide a formula for the base ionisation constant, Kb, for

Using the base ionisation constants below, calculate the pKb of each base and the pKa of their conjugate acids. Order the bases and conjugate acids from strongest to weakest. Ammonia Kb = 1.8 × 105 M Diethylamine Kb = 8.6 × 104 M Pyridine Kb = 1.7 × 109 M

Briefly comment on the factors that determine the strength of the bases above.

Explain the trend below in terms of aqueous acid strength. H2O < HF < HI

Page Total:

Marks 11

CHEM1001

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Semester 1, 2017

Page 11 of 16

A concentrated solution of potassium chloride was added to an unknown solution containing thallium(I) chromate. Ksp(K2CrO4) = 3.4 × 105

Ksp(TlCl) = 1.86 × 104

Calculate the molar concentration of thallium ions in solution when thallium(I) chloride first precipitates.

Calculate the molar concentration of chromate ions when potassium chromate first precipitates.

The Ksp of potassium chloride is 21 at room temperature, how many grams of potassium chloride are required to make a 250 mL saturated solution in water.

Page Total:

Marks 6

CHEM1001

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Semester 1, 2017

Page 12 of 16

In the diagram add the phase transition labels to the phase boundaries. Complete the diagram by adding the triple (T) and critical (C) points.

Saturn’s moon of Titan has a similar average atmospheric pressure (1.5 atm) to that of Earth (1 atm), but a much lower average surface temperature of 94 K, compared to Earth’s of 287 K. On Titan, methane is a liquid but on Earth it exists as gas under normal conditions. With reference to phase diagrams, account for this difference.

For each of the compounds below, what is the dominant intermolecular force. Indicate on the diagram, the direction of any permanent dipole.

THIS QUESTION CONTINUES ON THE NEXT PAGE.

Page Total:

Marks 9

CHEM1001

Semester 1, 2017

Page 13 of 16

Explain why ice floats on water but frozen carbon dioxide does not float on liquid carbon dioxide.

Predict if salt water would freeze at a higher or lower temperature than pure water. Explain your answer.

Page Total:

Marks 5

CHEM1001

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Semester 1, 2017

Page 14 of 16

The platinum complex cis-diamminedichloridoplatinum (also known as cis-platin) is a proven anti-cancer drug, yet the trans form is inactive. Draw and label the two isomers of the complex, defining the type of isomerisation.

Explain why only the cis form is an active anticancer drug.

Hexaaminecobalt(III) chloride, [Co(NH3)6]Cl3 is a diamagnetic solid. Draw, fill, and fully label the d-orbital splitting diagram for this metal complex.

Explain why [Co(NH3)6]3+ is yellow-orange as an aqueous solution.

Page Total:

Marks 9

CHEM1001

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Semester 1, 2017

Page 15 of 16

Determine the overall order of reaction for the hydrolysis of ethyl acetate using the experimental data below. CH3COOC2H5 + OH  CH3COO + C2H5OH Run 1 2 3

[CH3COOC2H5] / M 0.05 0.1 0.1

[OH] / M 0.05 0.05 0.1

Initial rate/ M s1 0.025 0.05 0.1

For this reaction, calculate the rate constant, including units.

The addition of imidazole was found to catalyse the hydrolysis of ethyl acetate. Explain the role of catalysts in chemical reactions.

Page Total:

Marks 5

CHEM1001

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Semester 1, 2017

Page 16 of 16

From the diagram of a face-centred cubic cell, complete the table and determine how many atoms are in the unit cell.

Position

Number in that position

Fraction in unit cell

Overall contribution

Centre Face Edge Corner

A primitive unit cell has 1 atom in its unit cell. Calculate the packing efficiency.

Page Total:

Marks 5...