Exam 3 Practice Exam - Chapters 7, 8, 9

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CHEM 120 Exam 3 Practice Test Autumn 2021 (Cover Page) Chapters 7, 8, 9 FULL NAME STUDENT # SECTION TA NAME EXAM INFORMATION You will have 45 minutes to complete the exam. There are 15 total questions. The points assigned to each question are outlined below. Please allot your time accordingly. Please write in pencil or pen and include your name at the top of each page of the exam. Any calculations can be performed using a scientific (non-graphing) calculator. Graphing calculators and any devices that have cellular service or web access are not permitted. All multiple choice questions must be answered in the grid at the bottom of the page. Please show all of your work on the free response questions, include all formulas used, and give all values with appropriate units. Formula, equations, units, and significant figures may all have points assigned in the partial credit scheme. Following the submission of your exam, it will be scored according to a standard key/rubric including partial credit on some free response questions. The full key will be available to you during Dr. R’s drop in office hours (BAG 202D) after the exams have been returned. You may contest your score through Gradescope within 5 business days of when the scores are published. Note that submitting a regrade request subjects your entire exam to regrading. QUESTION DESCRIPTION POINTS 1-10 Multiple Choice 20 points 11 12 13 14 15 TOTAL 50 POINTS
CHEM 120 Exam 3 Practice Test Autumn 2021 (Cover Page) This Page Intentionally Left Blank.
CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 1 of 7 Multiple Choice. 1. According to Boyle’s Law, which of the following is FALSE ? a. Doubling the pressure of a system requires compressing the sample into half the volume. b. Increasing the volume of the sample will result in a higher pressure reading. c. When the volume of a gas container is tripled, the new pressure will be 1/3 of the original. d. Volume and pressure are inversely proportional. 2. Which of these liquids do you expect has the HIGHEST boiling point? a. Propane (C 3 H 8 ) b. Butane (C 4 H 10 ) c. Acetone (C 3 H 6 O, shown) d. Propanol (C 3 H 8 O, shown) 3. Which of these statements about vapor pressure is FALSE ? a. The vapor pressure of a boiling liquid is equal to the atmospheric pressure. b. A solution with a high vapor pressure likely has a high boiling point. c. Liquids with hydrogen bonds have a low vapor pressure. d. Solutions with the strongest intermolecular forces likely have low vapor pressures and high boiling points. 4. Which of these is TRUE for any system at equilibrium? a. The forward reaction is faster than the reverse reaction. b. The reaction is exothermic if heat is released. c. The rate of the forward reaction is equal to the rate of the reverse reaction. d. There are an equal number of products and reactants present. 5. Which of these solutions would have the HIGHEST boiling point? a. Pure water b. 0.5 M potassium iodide c. 0.5 M potassium sulfide d. 0.5 M potassium phosphate Q1 Q2 Q3 Q4 Q5
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CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 2 of 7 6. When a cell is placed in a hypertonic solution, a. Water enters the cell, leading to hemolysis. b. Salt enters the cell to increase the interior osmotic pressure. c. Water leaves the cell, leading to crenation. d. The osmotic pressure of the solutions are equal. 7. Which of these statements is TRUE for all exothermic reactions? a. The temperature of the reactants will increase during the reaction. b. The reaction will release heat to the surroundings. c. The energy of the products is higher than the energy of the reactants. d. The activation energy is greater than the released energy. 8. Which of these reactions is a single-displacement reaction? a. Zn (s) + Cu(NO 3 ) 2 (aq) > Zn(NO 3 ) 2 (aq) + Cu (s) b. Mg (s) + O 2 (g) → MgO (s) c. AgNO 3 + KCl (aq) → AgCl (s) + KNO 3 (aq) d. 2 H 2 O 2 (aq) → 2 H 2 O (l) + O 2 (g) 9. What effect will decreasing the temperature of liquid acetone from 15 °C to 0 °C have on the rate of evaporation? a. Increase the rate of evaporation by more than 15% b. Increase the rate of evaporation by less than 15% c. Decrease the rate of evaporation d. Rate of evaporation will be unchanged. 10. What is the osmolarity of a solution containing 0.5 M Ca(H 2 PO 4 ) 2 ? a. 0.25 osM b. 0.5 osM c. 1.0 osM d. 1.5 osM Q6 Q7 Q8 Q9 Q10
CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 3 of 7 11. Gas Laws a. At constant temperature, a sample of 3.35 L of N 2 at 3.0 atm pressure is compressed until the new volume reaches 1.35 L. What is the new pressure? b. A balloon (with an ambient pressure of 1.00 atm) contains 0.31 grams of helium. If the balloon is heated from 295 K to 355 K and allowed to expand, what is the final volume of the balloon? c. A sample of gas is in a sealed container. Suppose the pressure in the container is quadrupled and the volume is halved. If the initial temperature is 30°C, what is the final temperature?
CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 4 of 7 12. Partial Pressures Suppose you had a large flask (5.50 L total volume) that was divided into two compartments by a valve. On the left side of the flask (3.00 L), there was a sample of Ne gas. On the right side of the flask (2.50 L), there was a sample of nitrogen gas (N 2 ). When the valve is opened, both gases are allowed to mix and fill the container (at constant temperature). a. If there are 2 neon atoms for every nitrogen molecule present, and the partial pressure of nitrogen gas in the final container is 1.0 atm, what is the total pressure in the flask after the valve is opened? b. If there are 8.193 grams of Ne present, what is the temperature of the flask?
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CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 5 of 7 Colligative Properties a. A solution of aluminum nitrate is made by dissolving 135.59 grams in 0.645 kg of water. Relative to pure water, the resulting solution has: (circle one answer per line) higher boiling point lower pointing point higher vapor pressure lower vapor pressure higher melting point lower melting point b. For the solution described in part a, what is the new boiling point if the aluminum nitrate dissolves fully into its ions in the aqueous solution?
CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 6 of 7 13. Circle to indicate conditions that will cause the described change. Which of these will kinetically speed up the reaction shown? 𝑪 𝟐 𝑯 𝟒 (𝒈) + 𝑪𝒍 𝟐 (𝒈) 𝒄𝒂?𝒂𝒍𝒚?? = 𝑯 + 𝑪 𝟐 𝑯 𝟒 𝑪𝒍 𝟐 (𝒈) Increase Pressure of Cl 2 Increase acid concentration Decrease Decrease Which of these will cause the thermodynamic equilibrium of this reaction to shift to the left? 𝑪𝑶 𝟐 (𝒈) + 𝑯 𝟐 (𝒈) ??𝒍?𝒆?? = ?𝒂?𝒆? 𝑯𝑪𝑶 𝟐 𝑯 (𝒂?) Increase overall pressure Increase concentration of formic acid (HCO 2 H) Decrease Decrease 14. Identify each of the following in the reaction shown: Fe 2 (SO 4 ) 3 ( aq ) + Zn ( s ) → ZnSO 4 ( aq ) + Fe ( s ) e. What element is reduced? f. What element is oxidized? g. Which chemical species is the oxidizing agent? h. Which chemical species is the reductant?
CHEM 120 Exam 3 Practice Test Autumn 2021 Exam Page 7 of 7 15. Give the oxidation state of each atom as requested below. Be clear whether the oxidation state is positive or negative. HNO 3 H = N = O = N 2 O N = O = HCl H = Cl = SO 2 S = O = KMnO 4 K = Mn = O = CaCl 2 Ca = Cl = [Cr 2 O 7 ] 2‒ Cr = O = 16. Identify the type (class) of reaction for each reaction equation given below. H 2 O 2 ( aq ) → H 2 O ( l ) + O 2 ( g ) Na 2 S ( aq ) + 2 HCl ( aq ) → 2 NaCl ( aq ) + H 2 S (g)
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CHEM 120 Exam 3 Practice Test Autumn 2021 Helpful Information Page HELPFUL INFORMATION PAGE R = 8.324 J mol -1 K -1 PV = nRT R = 0.0821 L atm mol -1 K -1 N A = 6.022 x 10 23 Temp (K) = Temp (°C) + 273.15 760 torr = 760 mmHg = 1 atm = 101.325 kPa