CHEM104 Midterm 1 PDF Fall 2024

**DO NOT OPEN THE TEST UNTIL YOU ARE TOLD TO DO SO** CHEM104 -002/003 General Chemistry I Fall 2024 Midterm I Instructor: Dr. Vince Guo October 23, 2024, 3:30 pm...

**DO NOT OPEN THE TEST UNTIL YOU ARE TOLD TO DO SO** CHEM104 -002/003 General Chemistry I Fall 2024 Midterm I Instructor: Dr. Vince Guo October 23, 2024, 3:30 pm-4:20 pm 50 minutes Name: ______________________________________________________________________ Student Number: ______________________________________________________________ Materials Supplied: This Test (8 pages) Scantron Spare paper for rough work Periodic Table and Constants, Equations are provided on pages 7 and 8 Allowed Aids: Pen, Pencil, Non-graphing calculators. Instructions: 1. Write your name and student number at the top of this page. 2. Write your answers for Part A in the space provided. Answers written elsewhere will not be marked. 3. Underline your final answer in Part A. 4. Record the answers to the multiple-choice questions on the Scantron sheet. 5. At the end of the test, slip the scantron into the test booklet and hand back. Important Notes: 1. The test is double sided. 2. Read through the questions carefully and answer what is being asked. 3. There is only one answer for each multiple-choice question. 4. Scantrons must be filled with pencil ONLY. 5. No extra time will be provided to fill in the scantrons. 6. Students should finish all the questions independently, any type of cheating on the exam is considered serious academic misconduct and will be reported to the Associate Dean Academic for investigation. Page 1 of 8 Part A: Short Answers (10 points total). Please provide the answers in the space provided. Report your final answer to the correct significant figures and units. Complete calculation work must be shown for full marks. Consider the following reaction for parts (a) – (e): CH3OH(l) + O2 (g) → CO2(g) + H2O(g) 45.5 grams of CH3OH(l) are reacted with 39.0 grams of O2 (g). (a) Balance the above chemical reaction (report the coefficients as the whole numbers). (b) Calculate the mass (in grams) of CO2 (g) formed from 45.5 grams of CH3OH(l). (c) Calculate the mass (in grams) of CO2 (g) formed from 39.0 grams of O2 (g). (d) Identify the limiting reagent. Answer: __________________________ (e) Calculate the amount (in moles) of excess reagent remains assuming complete reaction. Page 2 of 8 Part B: Multiple Choice Questions (2 points for each question, 40 points total). Please provide all the answers on the Scantron sheet. Only the answers provided on the Scantron sheet will be graded. 1. Which of the following processes is/are chemical change(s)? (a) Combustion of methane in oxygen to form carbon dioxide and water (b) Mixing cream with coffee (c) Freezing of water to ice (d) Answers (a) and (b) (e) Answers (a), (b) and (c) 2. What is the chemical name of Mg(ClO2)2? (a) Magnesium chlorate (b) Magnesium chloride (c) Magnesium chlorite (d) Magnesium hypochlorite (e) Magnesium perchlorate 3. How many electrons are present in Cr+? (a) 21 (b) 22 (c) 23 (d) 24 (e) 25 4. How many neutrons are present in 37Cl? (a) 17 (b) 18 (c) 19 (d) 20 (e) 21 5. Which of the following answers should be reported for the mathematical operation below? (4.81221 + 5.121) × (14.812 – 7.12988) = (a) 76.3 (b) 76.31 (c) 76.308 (d) 76.3081 (e) 76.30811 6. A laboratory analysis of an unknown sample yields 68.53% carbon, 8.64% hydrogen, and 22.83% oxygen. What is the empirical formula of the sample? (a) C4H6O (b) C4H7O (c) C4H8O (d) C4H9O (e) C5H9O Page 3 of 8 7. If a molecule with an empirical formula C2H2O has a molar mass of 210.20 g/mol, what is its molecular formula? (a) C2H2O (b) C4H4O2 (c) C6H6O3 (d) C8H8O4 (e) C10H10O5 8. Determine the oxidation state of phosphorus in PO2+. (a) +1 (b) +2 (c) +3 (d) +4 (e) +5 9. When the following equation is balanced, the coefficient of O2 is ________. NH3 (g) + O2 (g) → NO2 (g) + H2O (g) (a) 3 (b) 4 (c) 5 (d) 6 (e) 7 10. Which of the following substances is/are non-electrolyte(s)? (a) Acetic acid (b) Ammonia (c) Ethanol (alcohol) (d) Answers (a) and (b) (e) Answers (a), (b) and (c) 11. The gas density of water in a room measuring 4.12 m × 5.44 m × 2.55 m is 0.287 μg/cm3. Calculate the mass (in grams) of water present in the room. (a) 1.64 x 10-7 g (b) 1.64 x 10-5 g (c) 1.64 x 101 g (d) 1.64 x 105 g (e) 1.64 x 107 g 12. Which of the following substances is/are NOT molecules(s)? (a) C2H2 (b) H2 (c) Xe (d) Answers (a) and (b) (e) Answers (a), (b) and (c) Page 4 of 8 13. Consider the following reaction: 2Cr(NO3)3(aq) + 3Mg(s) → 3Mg(NO3)2(aq) + 2Cr(s) Identify the oxidizing agent of the reaction. (a) Cr(s) (b) Cr(NO3)3(aq) (c) Mg(s) (d) Mg(NO3)2(aq) (e) NO3-(aq) 14. As discussed in the textbook, 1 handle bar, 1 seat, 1 frame, two pedals and two wheels are required to assemble a bicycle. Suppose there are 4 handle bars, 4 seats, 3 frames, 7 pedals and 5 wheels, identify the limiting component. (a) Frame (b) Handle bar (c) Pedals (d) Seat (e) Wheel 15. How many oxygen atoms are present in 0.412 moles of Fe2O3? (a) 2.48 x 1023 oxygen atoms (b) 4.96 x 1023 oxygen atoms (c) 7.44 x 1023 oxygen atoms (d) 2.48 x 1024 oxygen atoms (e) 4.96 x 1024 oxygen atoms 16. Determine the mass of iron in grams of 7.24 x 1022 iron atoms. (a) 0.120 g (b) 6.71 g (c) 465 g (d) 1.30 x 1021 g (e) 4.04 x 1024 g 17. Determine the volume (in L) of solution needed to make a 0.118 M aqueous solution when 22.4 g of CaCl2 is dissolved in water. (a) 0.00171 L (b) 0.00585 L (c) 0.0238 L (d) 1.71 L (e) 5.85 L Page 5 of 8 18. Which of the following substances is/are soluble in water? (a) CuCl2 (b) Na2CO3 (c) Zn(OH)2 (d) Answers (a) and (b) (e) Answers (a), (b) and (c) Please use the following oxidation half-reactions of the activity series (the oxidation half reactions at the top being more reactive) to answer questions 19 and 20. 19. Which of the following metals will react with Cu2+(aq)? (a) Chromium (b) Manganese (c) Nickel (d) Answers (a) and (b) (e) Answers (a), (b) and (c) 20. Which of the following metals is the strongest reducing agent? (a) Aluminum (b) Copper (c) Gold (d) Lithium (e) Silver END OF EXAMINATION Page 6 of 8 The Periodic Table Solubility Rules Page 7 of 8  Physical Constants and Equations K = C + 273.15 1 cm = 1 x 10-2 m 1 μg = 1 x 10-6 g 1 kg = 1000 g Avogadro’s number: 1 mole = 6.02214 x 1023 individual units Molar mass = mass in grams of 1 mole of the substance difference from known value % error = ×100% known value Mass Density = Volume mass of part Mass Percent (%) of element= ×100% mass of compound Actual yield Percent yield (%) = ×100% Theoretical yield moles of solute Molarity = Liter of solution Page 8 of 8