PRACTICE CHEMISTRY PLACEMENT EXAM

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  1. An atom with an electron configuration of 1s2 2s2 2p3 has how many valence electrons?
    Khan Academy: Electron ConfigurationsOpens in new window ; Wyzant: Atomic StructureOpens in new window  
    1. 2
    2. 3
    3. 4
    4. 5 (must use highest shell electrons only—2+3)
    5. 7
  2. The  ___ sublevel of an atom has a total of five orbitals.
    Khan Academy: Quantum Numbers and OrbitalsOpens in new window ; Wyzant: Atomic StructureOpens in new window
    1. s (all s-sublevels have just one orbital)
    2. p (all p-sublevels have three orbitals)
    3. d
    4. f (all f-sublevels have seven orbitals)
    5. g (all g-sublevels have nine orbitals)
  3. You give a child a balloon, and he goes outside with it to play in the snow. Soon, he returns crying. What happened?
    Khan Academy: Ideal Gas EquationOpens in new window ; Wyzant: GasesOpens in new window
    1. The balloon expanded and burst.
    2. The balloon froze solid.
    3. The balloon shrank. (pressure and temperature directly proportional)
    4. The balloon dissolved.
    5. The child forgot Charles’ Law.
  4. What kind of bonding occurs in the compound potassium oxide?
    Khan Academy: Types of Chemical BondsOpens in new window
    1. ionic (strongly metallic elements, K, and electronegative nonmetals, O, form ionic bonds)
    2. nonpolar covalent
    3. polar covalent (double bond)
    4. polar covalent (single bond)
    5. None of the above
  5. A gas with a temperature of 21.0oC and a volume of 10.0 L is compressed to 5.00 L. What will be the new temperature?
    Khan Academy: Ideal Gas EquationOpens in new window ; Wyzant: GasesOpens in new window
    1. 10.5 oC (don’t forget to change temperatures to Kelvin)
    2. 420. oC (don’t forget how to change to Kelvin back to Celsius)
    3. 42.0 oC (several of the above went wrong!)
    4. –126 oC
    5. 315 oC (mixed up initial and final conditions)
  6. Which of the following sublevels does not exist as written?
    Khan Academy: Quantum Numbers and OrbitalsOpens in new window
    1. 3f (the fourth f-sublevel appears for the first time in the fourth shell)
    2. 6f
    3. 2s
    4. 5d
    5. 8s (the number of sublevels—s, p, d, f, etc.—increase by one as the main energy level increases by one)
  7. What is the molecular shape of PH3? 
    Khan Academy: Hybridization and Hybrid OrbitalsOpens in new window
    1. tetrahedral (the lone electron pair isn’t counted in the shape)
    2. trigonal planar (don’t forget to include the lone electron pair)
    3. bent
    4. linear
    5. trigonal pyramidal
  8. What is the percent by mass concentration of sodium bromide in a solution which contains 50.0 g of sodium bromide in 200.0 g of water?
    Wyzant: SolutionsOpens in new window
    1. 40.0 %
    2. 20.0 %
    3. 25.0 % (forgot to add 50+250 for the total solution mass)
    4. 33.3 %
    5. 50.0 %
  9. How many milliliters of 6.00 M HCl solution would be required to prepare 2.00 L of 0.140 M HCl by dilution?
    Wyzant: SolutionsOpens in new window
    1. 420 mL (mixed up which volume needed to calculate total moles HCl)
    2. 168 mL
    3. 85.6 mL (moles x volume gives moles)
    4. 46.7 mL (2.00 x 0.140 gives total moles HCl; dividing that by 6.00 gives volume needed)
    5. 30.0 mL
  10. What is the molar concentration of 2000. mL of aqueous solution containing 135 g of glucose, C6H12O6?
    Wyzant: SolutionsOpens in new window ; Khan Academy: Introduction to the AtomOpens in new window
    1. 12.15 M (don’t forget how to correctly convert grams to moles)
    2. 0.750 M
    3. 67.5 M (don’t forget to change grams to moles)
    4. 0.667 M
    5. 0.375 M 
  11. What is the formula of copper (II) sulfate pentahydrate?
    Wyzant: CompoundsOpens in new window
    1. Cu2(SO4)2 . 5 H2O (ionic compounds written with simplest subscripts)
    2. Cu2(SO4) . 5 H2O (wrong charges on your ions)
    3. CuSO4 . 6 H2O (hexahydrate would be the correct name here)
    4. CuSO4 . 5 H2O
    5. None of the above
  12. What is the electron configuration for the nitride ion?
    Khan Academy: Electron ConfigurationsOpens in new window ; Wyzant: CompoundsOpens in new window
    1. 1s2 2s2 2p1
    2. 1s2 2s2 2p3 (this is just a nitrogen atom by itself)
    3. 1s2 2s2 2p5 (nitrogen needs to add three electrons to achieve the noble gas configuration)
    4. 1s2 2s2 2p6 (nitride has a negative three charge—adding three electrons to the N-atom)
    5. None of the above
  13. A tank has a pressure of 30.0 atm at a temperature of 22.0oC. After heating, the temperature rises to
    35.0oC. What is the new pressure?
    Khan Academy: Ideal Gas EquationOpens in new window ; Wyzant: GasesOpens in new window
    1. 54.3 atm
    2. 31.3 atm
    3. 28.7 atm (mixed up initial and final conditions—pressure should go up!)
    4. 47.7 atm (don’t forget to change temperature to Kelvin)
    5. 30.6 atm
  14. Which pair is immiscible?
    Wyzant: SolutionsOpens in new window ; Khan Academy: SolubilityOpens in new window
    1. ethanol and water (both are polar)
    2. water and octane, C8H18 (like dissolves like—water is polar, while octane is nonpolar)
    3. isopropyl alcohol and water
    4. acetic acid and water (both are polar)
    5. octane and oil (both are nonpolar)
  15. How many grams of sodium hydroxide are required to prepare 250.0 mL of a 6.00 M solution?
    Wyzant: SolutionsOpens in new window ; Khan Academy: Introduction to the AtomOpens in new window
    1. 1.50 g (these are the moles of sodium hydroxide needed—be sure to convert to grams)
    2. 0.0375 g (don’t forget how to convert moles to grams)
    3. 0.600 g (incorrect conversion of mL to L)
    4. 3.75 g (combined errors from b and c)
    5. 60.0 g 
  16. 5.60 L of a gas at STP has a mass of 13.0 g. What is the molar mass of the gas?
    Khan Academy: Ideal Gas EquationOpens in new window ; Wyzant: GasesOpens in new window
    1. 33.2 g/mol (keep in mind that STP = 273 K, 1 atm)
    2. 66.4 g/mol (1 mol of gas at STP = 22.4 L)
    3. 26.0 g/mol
    4. 52.0 g/mol
    5. none of the above
  17. What volume of 0.62 M sodium hydroxide is required to neutralize 20.00 mL of 0.391 M nitric acid? Word reaction with reactants only. (Students should predict products): Sodium hydroxide + nitric acid 
    Khan Academy: Balancing Chemical EquationsOpens in new window ; Wyzant: ReactionsOpens in new window , Basic StoichiometryOpens in new window
    1. 23.6 mL
    2. 16.9 mL
    3. 9.03 mL
    4. 11.8 mL
    5. none of the above (correct amount is 12.6 mL; the two reactants are in a 1:1 mol ratio)
  18. How many moles are in 20.0 g of sodium carbonate?
    Khan Academy: Introduction to the AtomOpens in new window ; Wyzant: Moles and PercentagesOpens in new window
    1. 1.89 mol (no unit conversions of grams are required)
    2. 212 mol
    3. 2.12 x 103 mol (remember how to correctly convert grams to moles)
    4. 0.189 mol
    5. 18.9 mol (no unit conversions of grams are required)
  19. The percent of nitrogen in magnesium nitride is
    Khan Academy: Molecular CompositionOpens in new window ; Wyzant: Moles and PercentagesOpens in new window , CompoundsOpens in new window
    1. 27.8%
    2. 36.6% (write correct formula for compound, remembering monatomic charges)
    3. 16.1%
    4. 72.2% (this is the mass percent of magnesium)
    5. 63.4% (write correct formula for compound, remembering monatomic charges)
  20. What is the molar concentration of 250. mL of aqueous solution containing 48.8 g of glucose, C6H12O6?
    Wyzant: SolutionsOpens in new window ; Khan Academy: Introduction to the AtomOpens in new window
    1. 5.12 M (combination of errors from b and e)
    2. 0.923 M (inverted the definition of molarity = moles ÷ volume in liters)
    3. 0.271 M
    4. 1.08 M
    5. 0.195 M (must convert grams to moles first) 
  21. How many grams of aluminum metal will react with 0.0500 mole of oxygen gas according to the unbalanced equation given? Aluminum + Oxygen -> Aluminum Oxide
    Khan Academy: StoichiometryOpens in new window ; Wyzant: Basic StoichiometryOpens in new window
    1. 1.35 g (first balance equation to convert moles diatomic oxygen to moles aluminum)
    2. 1.01 g
    3. 4.32 g
    4. 2.06 g
    5. 1.80 g
  22. For the equation given, how many grams of methane will react with 125 g of oxygen? Word reaction with reactants only. (Students should predict products):
    Methane (CH4) burns in oxygen
    Khan Academy: StoichiometryOpens in new window ; Wyzant: Basic Stoichiometry Opens in new window
    1. 39.1 g
    2. 19.5 g
    3. 15.6 g
    4. 31.3 g
    5. 62.5 g (must use diatomic oxygen and its molar mass in this calculation)
  23. For problems 24 - 25, Given the word reaction with reactants only (students should predict products):
    phosphoric acid reacts with magnesium carbonate
  24. From the balanced chemical equation the simplest whole number coefficient for the product magnesium phosphate is:
    Khan Academy: Balancing Chemical EquationsOpens in new window ; Wyzant: ReactionsOpens in new window
    1. 1
    2. 2 (be sure to use correct charges on ions when balancing)
    3. 3
    4. 4
    5. none of the above
  25. If 50.0 g of magnesium carbonate reacts completely with phosphoric acid, the grams of gas produced is:
    Khan Academy: Balancing Chemical EquationsOpens in new window ; Wyzant: ReactionsOpens in new window , Basic StoichiometryOpens in new window
    1. 52.2 g
    2. 26.1 g
    3. 13.1 g
    4. 50.0 g (balance the equation to start, then convert reactant grams to moles)
    5. 55.0 g (the gas produced is carbon dioxide, molar mass = 44.01 g/mol)
  26. How many molecules are in 5.8 g of acetone, C3H6O?
    Khan Academy: Atomic Mass and MolesOpens in new window ; ChemTutor: Moles and PercentagesOpens in new window
    1. 0.10 molecules (this is the number of moles, not molecules)
    2. 6.0 x 1022 molecules
    3. 3.5 x 1024 molecules
    4. 6.0 x 1023 molecules (this is roughly Avogadro’s number, the number molecules in a mol)
    5. none of the above
  27. This reaction is an example of which of the following types? Aluminum reacts with bromine to produce aluminum bromide
    Wyzant: ReactionsOpens in new window
    1. combination (two or more reactants produce a single product)
    2. single displacement
    3. decomposition
    4. gas formation
    5. precipitation
  28. What is the simplest whole number coefficient for aluminum bromide in the above reaction (#27)?
    Khan Academy: Balancing Chemical EquationsOpens in new window ; Wyzant: ReactionsOpens in new window
    1. 1 (recall that bromine is diatomic, as well as the correct charges on the monatomic ions)
    2. 2
    3. 3
    4. 4
    5. none of the above
  29. How many moles of oxygen are required for the complete reaction of 45 g of C2H4 when it is burned?
    Khan Academy: Balancing Chemical EquationsOpens in new window , StoichiometryOpens in new window ; Wyzant: ReactionsOpens in new window , Basic StoichiometryOpens in new window
    1. 1.3 x 102 mol (balance the equation to start, then convert reactant grams to moles)
    2. 0.64 mol
    3. 112.4 mol
    4. 4.8 mol
    5. none of the above
  30. If 14.0 g of C2H4 is burned and the actual yield of water is 7.84 g, the percent yield in the reaction is: 
    Khan Academy: Balancing Chemical Equations, Stoichiometry; Wyzant: ReactionsOpens in new window , Stoichiometry Opens in new window
    1. 0.56%
    2. 43.6%
    3. 87.1% (be sure to balance the equation and convert moles reactant to moles product)
    4. 56.0%
    5. 82.0%

Answers:

1d 2c 3c 4a 5d 6a 7e 8b 9d 10e 11d 12d 13b 14b 15e 16d 17e 18d 19a 20d 21e 22d 23(NA) 24a 25b 26b 27a 28b 29d 30b