CHEM11041 - Term 1 Standard Examination 2016 Chemistry for the Life Sciences 2016

Term 1 Standard Examination 2016 Chemistry for the Life Sciences CHEM11041 Instructions Sheet 1. Write all answers in the Examination Answer Booklet provided. 2. You have 2 hours to complete this examination. 3. Students must answer all five questions. 4. All questions are of equal value – 20 marks each. Allow approximately 1 minute per mark. (5 questions x 20 marks = 100 marks total) 5. Write your answers clearly; Number your questions clearly; i.e. Question 2 (a). 6. During the perusal time notes can only be made on the rough working paper. 7. Show all working or reasoning for your answers. 8. A template for Lewis dot diagram and VSEPR calculations is provided at the end of this paper. 9. A copy of a Periodic Table is provided at the end of this paper. 10. General data and useful equations are provided at the end of this paper. Term 1 Standard Examination 2016Chemistry for the Life Sciences CHEM11041 Question 1 (Periodic Table, Gas Laws and Nuclear Chemistry) a) Carbon-13 is a natural isotope of carbon that is used in carbon dating, to estimate the age of once living material.   i) How does carbon-13 compare to carbon-12 in terms of the number ofprotons, neutrons and electrons present?      (3 marks) ii) Write the element symbol of each isotope using superscripts and subscriptsto indicate atomic mass and number.    (2 marks)     b) By looking at the Periodic Table, predict which of the following atoms would be thelargest:   Magnesium, Phosphorus or Beryllium.  Explain your choice. (3 marks) c) In the formation of smog, nitrogen and oxygen gas react to form nitrogen dioxide.How many grams of nitrogen dioxide, NO2, will be produced when 2.00 L ofnitrogen at 1.00 atm pressure and 25.0 oC completely reacts according to thefollowing equation?         (8 marks)            N2(g) + O2(g) --- 2NO(g)  d) Calcium-47 decays via beta emission and has a half-life of 4.5 days.i) Write a balanced nuclear equation for the beta decay of Ca-47. (2 marks) ii) How many days have passed if 4.8 mg of Ca-47 decays to just 0.6 mgof Ca-47?        (2 marks) Question 2 (Bonding) a) One of the ions of tin is tin(IV)i) Write a balanced equation for the reaction of tin (IV) with the oxide ion,showing the ionic state of the elements.  (2 marks) ii) Write the electronic configuration of each of the ions involved.  (2 marks) iii) Name the ionic compound formed.(2 marks) b) Explain why salt is often sprinkled on roads during European winters.  In youranswer consider the types of bonding and forces involved at a molecular level. (4 marks) c) Draw a valid Lewis Dot structure for H2NOH. By using VSEPR, comment on theshape around the central nitrogen atom.  (6 + 4=10  marks) Question 3 (Chemical reactions) a) The synthesis of aspirin (acetylsalicylic acid) can be represented by the followingchemical equation:                        i) If 3.0 g of salicylic acid, is used, along with 6.0 mL of acetic anhydride, predictwhich of these reagents would be the limiting reagent for this reaction.  Thedensity of acetic anhydride is 1.082 g / mL.    (6 marks) ii) Calculate the theoretical yield (in grams) of aspirin, based on your workings inpart i) of this question.        (4 marks) b) Consider the following exothermic reaction:         3H2(g) + N 2(g) -----> 2NH3(g) Predict what effect, if any, each of the following changes would have on thedirection of equilibrium in the reaction above. Explain your answers. i) Decrease in temperature      (2 marks) ii) Increase in nitrogen gas concentration.    (2 marks)iii) Adding a catalyst.       (2 marks) iv) Increase in ammonia concentration     (2 marks)v) Increase in pressure in reaction vessel.    (2 marks)  Question 4 (Solutions, Acid, base and buffer chemistry) a) Explain why the pH of 0.100 M HCl = 1.00 yet the pH of 0.100 M acetic acid is 2.88? (3 marks) b) What mass of NaOH would be required to prepare 100.00 mL of a 0.250 M NaOH solution? (4 marks) c) Calculate the pH of a 0.250 M NaOH solution. (3 marks) d) Consider the following equation representing the components of a buffer solution: i) Why would this buffer be most effective at minimizing pH change when the concentrations of HNO2 and NO2- are equal? (2 marks) ii) Given that pKa of HNO2 = 3.39, [HNO2] = 0.150 M and [NO2-] = 0.100 M, calculate the pH of this buffer. (4 marks) iii) What will the pH of the buffer be following a 1/10 dilution? Explain your answer. (2 marks) iv) How will the buffer capacity of the buffer be affected following a1 10 dilution? Explain your answer. (2 marks) Question 5 (Organic chemistry) a) Which of the following two compounds, butane or 1-pentanol, would have the highest boiling point? Explain your choice. (2 marks) b) Name the functional group present, and provide the IUPAC name for the following compound. (3 marks) c) Compound A, formula C4H8O, can be synthesized from 2-methyl-1-propanol. Compound A is known to oxidise and produce a carboxylic acid which we will refer to as compound B. Draw and name the compounds A and B. (6 marks) d) Draw cis-3,4-dimethyl-3-octene (5 marks) e) Draw the major product formed in each of the following reactions: End of Exam