SEMESTER 1 EXAMINATION 2009

THE UNIVERSITY OF THE SOUTH PACIFIC

CHP02 PRELIMINARY CHEMISTRY A

Time Allowed: 3 hours plus 10 minutes reading time. Total Marks: 100

INSTRUCTIONS TO CANDIDATES 1. There are three sections in this paper. All sections are compulsory. 2. Answer ALL questions in blue or black ink. 3. Section A is worth 20 marks, Section B is worth 30 marks, and Section C is

worth 50 marks. 4. Section A consists of 20 multiple-choice questions. Circle the letter that

represents the best answer to each question on the answer grid provided. 5. Sections B and C consists of numerical type questions requiring calculations.

Write your answers in the spaces provided on the question paper. If you need additional space, use the facing page.

6. Show all working clearly. Marks will be allocated on the basis of logical

working. 7. Calculators are permitted, provided they are not programmed before the start of

the examination. 8. Periodic Table and Fundamental Constants are provided at the end of this paper. 9. You are required to fill in your details below. STUDENT NAME: _________________________________________

STUDENT ID. NO: ________________________________________

CAMPUS: ________________________________________

Section A Multiple Choice ____ (20 marks) There are 20 multiple-choice questions. Circle the letter that represents the best answer in the answer grid provided. Each question is worth 1 mark.

1. What is the first step of the scientific method? A. Propose a hypothesis B. Develop a theory C. Establish a law D. Make reproducible observations 2. While performing an experiment in lab, a student records a physical measurement

4.45 in the lab notebook. This value is best described as A. highly precise B. accurate C. meaningless D. imprecise 3. Which of the following numbers has the fewest number of significant figures? 1235 0.30001 12000 10.00 A. 1235 B. 0.30001 C. 12000 D. 10.00 4. Which one of the following corresponds to the greatest mass? A. 1.70 x 102 g B. 0.75 kg C. 500 g D. 6.5 x 102 mg 5. Which individual is credited with developing the atomic theory? A. Democritus B. Aristotle C. Dalton D. Rutherford 6. Which one of the following does not naturally exist as a diatomic molecule? A. Helium B. Hydrogen C. Nitrogen D. Flourine

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7. Which one of the following statements does not characterize all gases? A. They are invisible. B. They have neither a definite shape nor a definite volume. C. They completely fill the container in which they are placed. D. Their fundamental particles move independently of one another. 8. A freshly opened can of soda poured over ice is classified as _________substance A. a pure B. a homogeneous C. an elemental D. a heterogeneous 9. How many elements are there in the 6th period of the periodic table? A. 2 B. 18 C. 32 D. 26 10. Which of the following is not a match? A. PO , phosphite ion −2

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B. OH-, hydroxide ion C. CrO , chromate ion −2

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D. ClO , chlorate ion −3

11. Having one mole of carbon dioxide means that you have A. 6.022 x 1023 moles of carbon. B. 6.022 x 1023 atoms of oxygen. C. 6.022 x 1023 molecules of carbon dioxide. D. 6.022 x 1023 molecules of carbon. 12. Which one of the following is not a major point of the kinetic molecular theory? A. Temperature of a gas is proportional to its average kinetic energy. B. Gas molecules exhibit negligible intermolecular forces. C. Gases completely fill the container they occupy. D. Gas molecules are in rapid, random motion. 13. Gases mix rapidly and thoroughly due to A. the low density of gases. B. the rapid and random motion of the molecules. C. the small nature of the molecular species. D. the temperature dependence of gas molecules.

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14. Arrange the following four gases in order of increasing average velocity, assuming they all exist at the same temperature: Kr, Cl2, N2O, SO3

A. Kr < Cl2 < N2O < SO3B. Cl2 < N2O < Kr < SO3C. N2O < Cl2 < SO3 < Kr D. Kr < SO3 < N2O < Cl2 15. As one descends from the top of a mountain, A. the atmospheric pressure increases. B. the atmospheric pressure decreases. C. the atmospheric pressure increases, then decreases. D. the atmospheric pressure remains constant. 16. What volume does a gas occupy if 2.5 moles exert a pressure of 977 torr at 32 0C? A. 49 dm3

B. 6.7 cm3

C. 5.1 dm3

D. 64 cm3

17. Which one of the following materials would not be classified as an amorphous

solid? A. A glass window B. Bicycle tire C. A sandwich plastic bag D. Table salt 18. The reason that metals are good conductors of electricity is that A. they have more electrons than nonmetals. B. they have a higher number of negative charges. C. their valence electrons are free to move about the crystal lattice. D. they have fewer electrons than nonmetals. 19. At the equilibrium vapor pressure of an enclosed liquid, A. the rate of condensation > the rate of evaporation B. the rate of condensation = the rate of evaporation C. the rate of condensation < the rate of evaporation D. no molecules either evaporate or condense

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20. A liquid with a higher equilibrium vapor pressure than another liquid can be attributed to

A. weaker intermolecular forces. B. a larger density. C. a higher surface tension. D. a higher boiling point.

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ANSWER SHEET SECTION A: Multiple Choice (20 marks) Circle the letter in the answer grid that represents the best answer to each question.

1 A B C D

2 A B C D

3 A B C D

4 A B C D

5 A B C D

6 A B C D

7 A B C D

8 A B C D

9 A B C D

10 A B C D

11 A B C D

12 A B C D

13 A B C D

14 A B C D

15 A B C D

16 A B C D

17 A B C D

18 A B C D

19 A B C D

20 A B C D

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Section B Short Answer Questions ___ (30 marks) There are 10 questions. Each question is worth 3 marks. 1) (a) Students in different class sections attempted to measure the mass of a 100.0 g

object. Describe the series of measurements as precise, precise and accurate, or neither. (1½ marks)

Class 1: 94.2 g, 93.8 g, 94.4 g, 94.0 g _____________________________

Class 2: 94.3 g, 89.7 g, 102.4 g, 97.8 g _____________________________

Class 3: 100.2 g, 100.0 g, 99.8 g, 99.8 g _____________________________

(b) Round off each of the following numbers to the number of significant figures

indicated in brackets. (1½ marks) (i) 115 (2) (ii) 1.0080 (3) (iii) 1.45 (2) 2) (a) Identify the following as either a physical or a chemical property. (1½ marks) (i) Diamond is one of the hardest known substances _________________________

(ii) Soap is slippery ___________________________

(iii) Gold does not rust _________________________

(b) Identify the following as homogeneous or heterogeneous matter. (1½ marks)

(i) Gasoline _________________________________

(ii) Air _____________________________________

(iii) Alcohol _________________________________

3) (a) Name the following compounds. (1½ marks)

(i) LiF

(ii) AlCl3

(iii) Mg(OH)2

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(b) Write down the formulas for the following compounds. (1½ marks)

(i) Copper (II) sulfide _____________________________

(ii) Lead (II) chloride _____________________________

(iii) Sulfur trioxide _________________________________

4) What is the percent composition of all of the elements in limestone (CaCO3)?

(3 marks) 5) A balloon can hold 1000 cm3 of air before busting. The balloon contains 875 cm3

of air at 8 0C. Will it burst when it is taken to another place with a temperature of 30 0C? (Assume that the pressure of the gas in the balloon remains constant).

(3 marks)

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6) (a) When a fuel tank is filled up no more fuel can be added. But when a car tyre is “filled”, more air can be added. Explain. (1½ marks)

(b) (i) State the Boyle’s Law of gases. (½ marks) (ii) Explain Boyle’s Law of gases using kinetic molecular theory. (1 mark) 7) A sample of gas occupies 500 cm3 at STP. Calculate its volume at 45 oC and 1.5

atm pressure. (3 marks)

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8) How much water needs to be added to 25.0 cm3 of 15.6 M HNO3 in order to dilute it to a 2.5 M solution? (3 marks)

9) Classify each of the following crystalline solids as ionic, molecular, or metallic.

(2 marks) (i) Zinc ______________________________________

(ii) Zinc oxide _________________________________

(ii) Phosphorous _______________________________

(iv) Iodine monobromide ________________________

(b) State 2 ways in which the rate of dissolving can be increased. (1 mark) 10) Predict whether each of the following solvents is miscible or immiscible with

water. Also state which is polar and which is non polar. (3 marks) (i) Methanol (CH3OH) (ii) Carbon tetrachloride (CCl4) (iii) Lithium carbonate (Li2CO3)

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Section C Long Answer Questions (50 marks) There are 5 questions. Each question is worth 10 marks. 1) (a) A compound consists of magnesium, carbon and oxygen. It has 21.6 % Mg and

21.4 % C. Calculate its empirical formula. (3 marks) (b) A compound of nitrogen with molar mass of 92.0 g was found to have an

empirical formula of NO2. What is its molecular formula? (2 marks)

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(c) How many moles of H atoms will react with 2.5 moles of N to make NH3? (2 marks)

(d) Use the periodic table and write down the symbol of the element that fits each of the following descriptions. (3 marks)

(i) The fourth-period alkaline earth metal.

(ii) The liquid halogen.

(iii) The group IIIA metalloid

(iv) The last transition metal of the fifth period.

(v) The period 4, group 1A element.

(vi) The second noble gas.

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2) (a) Arrange the following items in increasing order of mass. (4 marks) 4.55 x 10 22 atoms of Pb 8.50 g of C 0.280 moles Ca (b) Calculate the amount (in grams) of Ca(OH)2 formed by reacting 17.0 g of CaO

with water. The equation for the reaction is CaO + H2O Ca(OH)2 Note: Mr [Ca(OH)2] = 74 g/mol and Mr (CaO) = 56 g/mol

(3 marks)

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c) (i) Write down the electron configuration and draw the atomic structure of sodium (Na). (1½ marks)

(ii) Using the electron-dot diagram, explain how chemical bonding occurs in sodium

chloride (NaCl). (1½ marks)

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3) (a) (i) A container holds two gases, A and B. Gas A has a partial pressure of 325 torr and gas B has a partial pressure of 488 torr. What percent of the molecules in the mixture is gas A? (2 marks)

(ii) Which law of gases have you applied when calculating percent of molecules of

gas A in part (i) above? (1 mark) (b) (i) What is the pressure (in atmospheres) exerted by a mixture of 12.0 g N2 and 12.0 g

O2 in a 2.5 L container at 25 0C? (3 marks)

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(ii) Calculate the partial pressure of N2 in the mixture of the gases in part (i) above. (2 marks)

(c) 4.0 dm3 of a gas was collected over water at 25 oC at a pressure of 95.6 kPa.

Pressure of water is 3.5 kPa at 25 oC. Calculate the pressure of dry gas. (2 marks) 4) (a) (i) The density of a gas was measured at 1.50 atm and 27 0C and found to be 1.95

g/dm3. Calculate the molar mass of this gas. (3 marks)

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(ii) Which gas could it most likely be? (1 mark) (b) If you had equal mass of helium (He), methane (CH4) and carbon dioxide (CO2)

gas, which gas would exert the highest pressure? (3 marks) (c) Atoms of metallic structures are packed together in 3 geometric arrangements,

Name the 3 types of metal crystal packing arrangements and state their coordination number. (3 marks)

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5) (a) The ionic compound, caesium chloride (CsCl), has a crystalline structure. A unit

cell of CsCl is illustrated below.

Cl- ions

Cs+ ions (i) How are the caesium and chloride ions arranged in this unit cell? (1 mark) (ii) What is the coordination number of chloride ions? Explain why this is so.

(1 mark) (iii) What is the coordination number of caesium ions? (½ mark) (iv) What is the coordination ratio of caesium chloride structure? (1 mark) (v) Compare the sizes of chloride and caesium ions. (½ mark) (vi) State the relationship between the value of the coordination number and the packing of atoms in a crystal. (1 mark)

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(b) Distinguish between intermolecular and intramolecular forces using an example. (2 marks)

(c) At 600 0C,the vapor pressure of liquid A is 25 kPa where as vapor pressure of liquid B is 50 kPa. Explain relative strengths of their

(i) boiling points (ii) heats of vaporisation (iii) intermolecular forces of attraction (3 marks)

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mol.KL.Torr

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