CHEM 120 Unit 4 Midterm Exam (Fall 2020) Introduction To General, Organic, And Biological Chemistry
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CHEM 120 Unit 4 Midterm Exam (Fall 2020) Introduction To General, Organic, And Biological Chemistry/CHEM 120 Unit 4 Midterm Exam (Fall 2020) Introduction To General, Organic, And Biological ChemistryCHEM 120 Unit 4 Midterm Exam (Fall 2020) Introduction To General, Organic, And Biological ChemistryC...
chem 120 unit 4 midterm exam fall 2020 introduction to general
and biological chemistrychem 120 unit 4 midterm exam fall 2020 introduction to general
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1. Joe conducts an experiment to test the effectiveness of a new drug for cancer. Which of the following variables
would be easiest to control? amount of drug administered
2. A mixture containing 50 grams of carbon and 75 grams of oxygen is sealed in a flask. The total mass of the
system is 225 grams. The flask is heated to cause the carbon and oxygen to react. The sealed flask is massed.
What is the mass of the sealed flask? 225 grams
3. Aluminum has a density of 2.7 g/cm3. What would be the mass, in g, of a block of aluminum with a volume of
15 cm3? 40.50 g
4. How many kilometers are in 800 m? 0.8 km
5. One mole is of carbon is equal to All of these.
6. The element iron (Fe) occurs naturally as four isotopes. Each of these isotopes has All of these
7. How many neutrons are in this isotope of tin? 66
8. The element with the ground state electron configuration of 1s2 2s2 2p6 3s2 3p5 is Cl.
9. The number of protons in a chloride ion, Cl-, is 17.
10. When barium reacts with iodine, barium ions, Ba2+, and iodide ions, I-, are formed. In this reaction, iodine
atoms gain electrons.
11. Which substance has ionic bonds? LiI
12. The name of the compound S2O3 is disulfur trioxide.
13. In a nonpolar covalent bond, electrons are shared equally.
14. The formula of magnesium nitride is Mg3N2.
15. Which is the electron dot structure of nitrogen?
16. Which atom is least likely to form an ion? Argon, Ar
17. The formula mass of CO2 is 32 g/mole.
18. How many moles of (NH4)2S are there in 75 g of (NH4)2S? 1.10
19. The molarity of a solution that contains 8.0 g of NaOH in a liter of solution is 0.20 M.
20. How many liters of a 20% ethanol solution can you prepare by diluting 5 liters of a 40% ethanol solution? 10
liters
21. A chemist makes a solution by dissolving 14 g of NaCl to a volume of 350 mL in water. What is the mass/
volume % concentration of this solution? 4% NaCl
22. How many oxygen atoms are in the formula for iron(III) oxide? 3
23. The best description of the shape of a boron trifluoride (BF3) molecule is trigonal planar.
24. Which of the following statements about molecules is correct? A compound that contains only polar bonds can
be nonpolar.
25. Match the compounds with their shapes: Tetrahedral- CF4 Bent- H2O Pyramidal- NH3 Linear-CO2
26. Match the ion or ground state atom to the correct number of electrons: 10 electrons-Oxide 18 electrons-
Potassium Ion 17 electrons- Chlorine 11 electrons-Sodium
27. Balance the equation: C3H8 + O2 → CO2 + H2O (6 points) C3H8 + 4 O2 → 3 CO2 + 4 H2O.
28. For the balanced chemical reaction: 2 HCl + Mg(OH)2 → MgCl2 + H2
1. Determine the MW of MgCl2. Show your work. (3 points)
2. Determine how many mols of HCl you would require to produce 20 grams of MgCl2. Show your work (3
points)
3. a. 58.3 g/mole. (1 point for work shown, 1 point for units, 1 point for correct answer)
4. b. 20 g MgCl2 x (1 mol MgCl.31 g MgCl2) x (2 mol HCl / 1 mol MgCl2) = 0.69 mols HCl (1 point
for conversions, 1 point for answer, 1 point for units)
29. How many ml of a 8 M KBr solution are required to produce 250 ml of a 2 M KBr solution? C1= 8 M, C2= 2
M, V2= 250 ml. V1=[(250 ml * 2 M) / 8 M) = 62.5 ml.
30. An isotope has a mass number of 67 and 39 neutrons. Determine the number of protons (2 points), number of
electrons (2 points) and the the chemical symbol of this isotope (2 points). 28 protons, 28 electrons, Ni.
31. Your daughter is an avid jump roper. The current brand that she uses, ACE, wears out within 1 week and has
recently worn out. You want to find a brand that lasts longer. Given the recent resurgence in this sport, there are
a number of manufacturers claiming to have high performance jump ropes. Teammate 1 says that brand TTT
"the best!”, Teammate 2 says that brand ZZZ "is cool!", and you also found a brand BBB jump rope at the
discount store. Use the scientific method to approach this scenario. Formulate a testable hypothesis (2 points).
Design an experiment to test your hypothesis, and include your controls and be specific in your experimental
design (4 points). Predict the experimental results that would support your hypothesis (2 points).
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