SCC-110 Sample Exam-2 with Answer Key Spring I 2021 PDF

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SCC 110: Foundations of Chemistry Sample Exam II – Spring I 2021 Instructions: 1. Do NOT open this exam until you are told to do so. Opening the exam before the start of the exam is considered an act of Academic Dishonesty. 2. All multiple-choice answers must be bubbled into the scantron answer sheet. 3. The response will be considered invalid if you bubble in more than one answer choice for a question. 4. You must use a #2 pencil to bubble in the answers on your scantron. 5. This exam booklet consists of a total of 12 pages (including periodic table). 6. No reference tables for this test. 7. Only scientific calculators are allowed (no graphing calculators) during the exam. 8. Questions 1-25 are 2 points each, and questions (26-30) are 10 points each. 9. On the FRONT of your scantron and on this title page. ➢ Write your last name, followed by your first name. 10. You will be handing in both the scantron and exam booklet at the end of the exam. 11. Cell phones and other electronic devices are not allowed. 12. Absolutely no restroom visits during the exam. 13. Neatness and clarity DO count.

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Some useful information Avogadro’s constant = 6.02 x 1023 R = 0.0821 L.atm/mole.K; R = 62.4 L.mmHg/mole.K 0 ˚C = 273 K , 1 atm = 760 torr; 1 atm = 760 mmHg 1. In any chemical reaction, the rate of the reaction can be increased by a) b) c) d) e)

decreasing the temperature changing the size of the container adding water to the reaction adding product molecules to the reaction mixture increasing the concentrations of the reactants

2. What is the concentration, in m/v percent, of a solution prepared from 50. g NaCl and 2.5 L of water? a) b) c) d) e)

5.0% 2.0% 0.020% 0.050% 20.%

3. What is the molarity of a solution that contains 17 g of NH3 in 500 mL of solution? a) b) c) d) e)

34 M 2.0 M 0.50 M 0.029 M 1.0 M

4. How many moles of CaCl2 are in 250 mL of a 3.0 M of CaCl2 solution? a) b) c) d) e)

750 moles 1.3 moles 83 moles 0.75 mole 3.0 moles

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5. What is the new mass/volume (m/v)% of a KOH solution that is prepared by diluting 110 mL of a 6% (m/v) KOH solution to 330 mL? a) b) c) d) e)

2% 1% 6% 12% 18%

6. A solution that has an osmotic pressure less than that of red blood cells is called a) b) c) d) e)

saturated hypertonic isotonic hypotonic unsaturated

7. A red blood cell will undergo crenation in a) b) c) d) e)

water 0.5% NaCl 3% glucose 5% glucose 7% NaCl

8. The solubility of KI is 50 g in 100 g of H2O at 20 °C. If 110 grams of KI are added to 200 grams of H2O, a) b) c) d) e)

all of the KI will dissolve the solution will freeze the solution will start boiling a saturated solution will form the solution will be unsaturated

9. Which of the following is NOT part of the kinetic theory of gases? a) b) c) d) e)

a gas is composed of very small particles there is very little empty space in a gas gas particles move rapidly gas particles do not attract or repel one another gas particles move faster when the temperature increases

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10. The atmospheric pressure in Denver, CO is 633 mmHg. What is this pressure in atm? a) 1.20 atm b) 633 atm c) 0.833 atm d) 1.00 atm e) 127 atm 11. In the reaction, N2O4 (g) 2 NO2 (g), decreasing the volume would make the reaction a) form more products b) form more reactants c) no effect on equilibrium d) increase the number of moles of reactant e) increase the number of moles of product 12. A balloon is filled with helium gas. For the question that follows, select the letter of the balloon diagram that corresponds to the given change in conditions.

The temperature is changed from 50 °C to -150 °C at constant pressure. a) A b) B c) C d) A and B e) B and C 13. A gas at 5.00 atm pressure was stored in a tank during the winter at 5.0 °C. During the summer, the temperature in the storage area reached 40.0 °C. What was the pressure in the gas tank then? a) 0.625 atm b) 4.44 atm c) 5.63 atm d) 40.0 atm e) 69.5 atm

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14. Given the following chemical reaction, H2(g) + I2(g) 2HI(g) what is the numerical value of Kc at 443 °C if the equilibrium concentrations are as follows? [H2] = 1.2 M [I2] = 1.2 M [HI] = 0.35 M

a) b) c) d) e) f)

8.5 x 10-2 4.11 11.75 0.85 0.1175 0.41

15. A diver exhales a bubble with a volume of 250 mL at a pressure of 2.4 atm and a temperature of 15 °C. What is the volume of the bubble when it reaches the surface where the pressure is 1.0 atm and the temperature is 27 °C? a) b) c) d) e)

580 mL 630 mL 100 mL 110 mL 1100 mL

16. A scuba tank contains a mixture of He and O2 gases at 10 atm. If the pressure of O2 gas is 1520 mmHg, what is the partial pressure of He gas in the tank? a) b) c) d) e)

2 atm 1510 mmHg 8 atm 12 atm 8 mmHg

17. If you balance the following equation the coefficient for H2O would be: Ca(OH)2 + H3PO4 → Ca3(PO4)2 + H2O a) b) c) d)

3 4 6 2

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18. How many molecules of water, H2O, are present in 75.0 g of H2O? a) 75.0 molecules b) 4.17 molecules c) 7.53 × 1024 molecules d) 2.51 × 1024 molecules e) 5.02 × 1024 molecules 19. Avogadro's number is the number of a) b) c) d) e)

particles in 1 mole of a substance amu in 1 mole of a substance grams in 1 mole of a substance moles in 6.02 × 1023 grams of an element moles in 6.02 × 1023 amu of an element

20. How many moles of carbon atoms are there in 0.500 mole of C2H6? a) b) c) d) e)

0.500 moles 1.00 moles 3.00 moles 6.02 × 1023 moles 4.00 moles

21. 0.100 mole of lithium weighs a) b) c) d) e)

3.00 g 0.300 g 6.94 g 0.694 g 0.700 g

22. Consider the following equation. 2Mg + O2 → 2MgO The number of moles of MgO produced when 0.20 mole of O2 reacts completely is a) b) c) d) e)

0.10 mole 0.20 mole 0.40 mole 0.60 mole 0.80 mole

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23. Calculate the grams of NaOH needed to prepare 2.00 L of a 2.50 M NaOH solution? a) b) c) d) e)

2.00 x 102 g 250 g 125 g 1.00 x 102 g 2.50 x 101 g

24. When the system A + B

C + D is at equilibrium,

a) the sum of the concentrations of A and B must equal the sum of the concentrations of C and D b) the forward reaction has stopped c) both the forward and the reverse reactions have stopped d) the reverse reaction has stopped e) neither the forward nor the reverse reaction has stopped 25. Calculate the volume in L of a 2.00 M KBr solution containing 3.00 moles of KBr. a) b) c) d) e)

1.50 L 6.66 L 6.00 L 0.666 L 0.600 L Short Answer Questions

26. a) Potassium chlorate (KClO3) decomposes upon slight heating in the presence of a catalyst, according to the reaction below. 2KClO3(s)→2KCl(s) + 3O2(g) If 40.0 g KClO3 is heated until it completely decomposes to produce 14.9 g of oxygen gas, what is the percent yield for the reaction? [8,2 pts]

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26. b) Consider this reaction: Zn(s) + Cl2(g) → ZnCl2(s) ➢ In the above reaction, Zn is reduced.

true or false (circle one)

➢ The above reaction is a single replacement reaction. true or false (circle one) 27. a) 0.226-g sample of carbon dioxide (CO2) has a volume of 525 mL and a pressure of 455 mmHg. Calculate the final temperature in degree Celsius. [7, 3 pts]

27. b) How many grams of C3H8 are burned if the reaction produced 297 g of CO2

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28. What is the molarity of 20.0 mL of a KCl solution that reacts completely with 30.0 mL of a 0.400 M Pb(NO3)2 solution? [10 pts] Pb(NO3)2(aq) + 2KCl(aq) → PbCl2(s) + 2KNO3(aq)

29. True or false Questions

[10 pts]

➢ A solute that is a nonelectrolyte dissolves as molecules true or false (circle one) ➢ CCl4 is soluble in water

true or false (circle one)

➢ LiCl dissolves in water

true or false (circle one)

➢ Solubility of a gas in a liquid decreases with increase in temperature true or false (circle one) ➢ When dissolved in 1 kg of water, 1 mole of C2H6O produces 9 moles of particles true or false (circle one)

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30. True or false Questions

[10 pts]

For the following two questions, consider a 4% starch solution and a 10% starch solution separated by a semipermeable membrane. ➢ A 10% starch solution has higher osmotic pressure than a 1% starch solution true or false (circle one) ➢ 10% starch solution will decrease in volume as osmosis occur true or false (circle one) -----------------------------------------------------------------------------------------------------------➢ Weak electrolytes produce solutions that conduct electricity weakly true or false (circle one) ➢ 1 mole of calcium nitrate produces two moles of particles true or false (circle one) ➢ Colloids are homogeneous mixtures that have solute particles that pass through filters but not semipermeable membranes true or false (circle one) Do not write answers below this line This space is intentionally left blank and may be used for scratch work

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This space is intentionally left blank and may be used for scratch work

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Sample Exam II – Key Question # Answer Choice 1 E 2 B 3 B 4 D 5 A 6 D 7 E 8 D 9 B 10 C 11 B 12 A 13 C 14 A 15 B 16 C 17 C 18 D 19 A 20 B 21 D 22 C 23 A 24 E 25 A Short answer questions 26-30 26. a) 40.0g KClO3 ×1mol KClO3/122.55gKClO3 × 3mol O2/2 mol KClO3 × 32.00 g O2/1 mol O2 = 15.7 g O2 (theoretical yield of O2) Actual yield =14.9g=14.9g; Theoretical yield =15.7g Percent Yield = 14.9 g / 15.7 g × 100% = 94.9% b) false, false

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27. a)

n = 0.226 g/44 g of CO2 = 0.00514 moles T = 455 mmHg x 0.525 L/62.4 L.mmHg/mole.K x 0.00514 = 744 K 744 K -273 = 471 C

b)

297 g CO2 × 1mol CO2/44.0 g CO2 × 1 mol C3H8/3 mol CO2 × 44.1 g C3H8/1 mol C3H8 = 99.2 g

28. 0.03 L x 0.400 moles of Pb(NO3)2/1L = 0.012 moles of Pb(NO3)2 0.012 moles Pb(NO3)2 x 2 moles of KCl/1 mole of Pb(NO3)2 = 0.024 moles of KCl 0.024 moles of KCl/0.02 L of KCl = 1.2 M KCl 29. true, false, false, true, false 30. true, false, true, false, true

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