PRACTICE CHEMISTRY PLACEMENT EXAM
with Weblinks for Self-Guided Tutorial
- An atom with an electron configuration of 1s2 2s2 2p3 has how many valence electrons?
Khan Academy: Electron Configurations ; Wyzant: Atomic Structure- 2
- 3
- 4
- 5 (must use highest shell electrons only—2+3)
- 7
- The ___ sublevel of an atom has a total of five orbitals.
Khan Academy: Quantum Numbers and Orbitals ; Wyzant: Atomic Structure
- s (all s-sublevels have just one orbital)
- p (all p-sublevels have three orbitals)
- d
- f (all f-sublevels have seven orbitals)
- g (all g-sublevels have nine orbitals)
- 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 Equation ; Wyzant: Gases- The balloon expanded and burst.
- The balloon froze solid.
- The balloon shrank. (pressure and temperature directly proportional)
- The balloon dissolved.
- The child forgot Charles’ Law.
- What kind of bonding occurs in the compound potassium oxide?
Khan Academy: Types of Chemical Bonds
- ionic (strongly metallic elements, K, and electronegative nonmetals, O, form ionic bonds)
- nonpolar covalent
- polar covalent (double bond)
- polar covalent (single bond)
- None of the above
- 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 Equation ; Wyzant: Gases
- 10.5 oC (don’t forget to change temperatures to Kelvin)
- 420. oC (don’t forget how to change to Kelvin back to Celsius)
- 42.0 oC (several of the above went wrong!)
- –126 oC
- 315 oC (mixed up initial and final conditions)
- Which of the following sublevels does not exist as written?
Khan Academy: Quantum Numbers and Orbitals
- 3f (the fourth f-sublevel appears for the first time in the fourth shell)
- 6f
- 2s
- 5d
- 8s (the number of sublevels—s, p, d, f, etc.—increase by one as the main energy level increases by one)
- What is the molecular shape of PH3?
Khan Academy: Hybridization and Hybrid Orbitals
- tetrahedral (the lone electron pair isn’t counted in the shape)
- trigonal planar (don’t forget to include the lone electron pair)
- bent
- linear
- trigonal pyramidal
- 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: Solutions
- 40.0 %
- 20.0 %
- 25.0 % (forgot to add 50+250 for the total solution mass)
- 33.3 %
- 50.0 %
- 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: Solutions
- 420 mL (mixed up which volume needed to calculate total moles HCl)
- 168 mL
- 85.6 mL (moles x volume gives moles)
- 46.7 mL (2.00 x 0.140 gives total moles HCl; dividing that by 6.00 gives volume needed)
- 30.0 mL
- What is the molar concentration of 2000. mL of aqueous solution containing 135 g of glucose, C6H12O6?
Wyzant: Solutions ; Khan Academy: Introduction to the Atom- 12.15 M (don’t forget how to correctly convert grams to moles)
- 0.750 M
- 67.5 M (don’t forget to change grams to moles)
- 0.667 M
- 0.375 M
- What is the formula of copper (II) sulfate pentahydrate?
Wyzant: Compounds- Cu2(SO4)2 . 5 H2O (ionic compounds written with simplest subscripts)
- Cu2(SO4) . 5 H2O (wrong charges on your ions)
- CuSO4 . 6 H2O (hexahydrate would be the correct name here)
- CuSO4 . 5 H2O
- None of the above
- What is the electron configuration for the nitride ion?
Khan Academy: Electron Configurations ; Wyzant: Compounds- 1s2 2s2 2p1
- 1s2 2s2 2p3 (this is just a nitrogen atom by itself)
- 1s2 2s2 2p5 (nitrogen needs to add three electrons to achieve the noble gas configuration)
- 1s2 2s2 2p6 (nitride has a negative three charge—adding three electrons to the N-atom)
- None of the above
- 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 Equation ; Wyzant: Gases- 54.3 atm
- 31.3 atm
- 28.7 atm (mixed up initial and final conditions—pressure should go up!)
- 47.7 atm (don’t forget to change temperature to Kelvin)
- 30.6 atm
- Which pair is immiscible?
Wyzant: Solutions ; Khan Academy: Solubility- ethanol and water (both are polar)
- water and octane, C8H18 (like dissolves like—water is polar, while octane is nonpolar)
- isopropyl alcohol and water
- acetic acid and water (both are polar)
- octane and oil (both are nonpolar)
- How many grams of sodium hydroxide are required to prepare 250.0 mL of a 6.00 M solution?
Wyzant: Solutions ; Khan Academy: Introduction to the Atom- 1.50 g (these are the moles of sodium hydroxide needed—be sure to convert to grams)
- 0.0375 g (don’t forget how to convert moles to grams)
- 0.600 g (incorrect conversion of mL to L)
- 3.75 g (combined errors from b and c)
- 60.0 g
- 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 Equation ; Wyzant: Gases
- 33.2 g/mol (keep in mind that STP = 273 K, 1 atm)
- 66.4 g/mol (1 mol of gas at STP = 22.4 L)
- 26.0 g/mol
- 52.0 g/mol
- none of the above
- 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 Equations ; Wyzant: Reactions , Basic Stoichiometry
- 23.6 mL
- 16.9 mL
- 9.03 mL
- 11.8 mL
- none of the above (correct amount is 12.6 mL; the two reactants are in a 1:1 mol ratio)
- How many moles are in 20.0 g of sodium carbonate?
Khan Academy: Introduction to the Atom ; Wyzant: Moles and Percentages- 1.89 mol (no unit conversions of grams are required)
- 212 mol
- 2.12 x 103 mol (remember how to correctly convert grams to moles)
- 0.189 mol
- 18.9 mol (no unit conversions of grams are required)
- The percent of nitrogen in magnesium nitride is
Khan Academy: Molecular Composition ; Wyzant: Moles and Percentages , Compounds- 27.8%
- 36.6% (write correct formula for compound, remembering monatomic charges)
- 16.1%
- 72.2% (this is the mass percent of magnesium)
- 63.4% (write correct formula for compound, remembering monatomic charges)
- What is the molar concentration of 250. mL of aqueous solution containing 48.8 g of glucose, C6H12O6?
Wyzant: Solutions ; Khan Academy: Introduction to the Atom- 5.12 M (combination of errors from b and e)
- 0.923 M (inverted the definition of molarity = moles ÷ volume in liters)
- 0.271 M
- 1.08 M
- 0.195 M (must convert grams to moles first)
- 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: Stoichiometry ; Wyzant: Basic Stoichiometry- 1.35 g (first balance equation to convert moles diatomic oxygen to moles aluminum)
- 1.01 g
- 4.32 g
- 2.06 g
- 1.80 g
- 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: Stoichiometry ; Wyzant: Basic Stoichiometry- 39.1 g
- 19.5 g
- 15.6 g
- 31.3 g
- 62.5 g (must use diatomic oxygen and its molar mass in this calculation)
-
For problems 24 - 25, Given the word reaction with reactants only (students should predict products):
phosphoric acid reacts with magnesium carbonate - From the balanced chemical equation the simplest whole number coefficient for the product magnesium phosphate is:
Khan Academy: Balancing Chemical Equations ; Wyzant: Reactions- 1
- 2 (be sure to use correct charges on ions when balancing)
- 3
- 4
- none of the above
- If 50.0 g of magnesium carbonate reacts completely with phosphoric acid, the grams of gas produced is:
Khan Academy: Balancing Chemical Equations ; Wyzant: Reactions , Basic Stoichiometry
- 52.2 g
- 26.1 g
- 13.1 g
- 50.0 g (balance the equation to start, then convert reactant grams to moles)
- 55.0 g (the gas produced is carbon dioxide, molar mass = 44.01 g/mol)
- How many molecules are in 5.8 g of acetone, C3H6O?
Khan Academy: Atomic Mass and Moles ; ChemTutor: Moles and Percentages- 0.10 molecules (this is the number of moles, not molecules)
- 6.0 x 1022 molecules
- 3.5 x 1024 molecules
- 6.0 x 1023 molecules (this is roughly Avogadro’s number, the number molecules in a mol)
- none of the above
- This reaction is an example of which of the following types? Aluminum reacts with bromine to produce aluminum bromide
Wyzant: Reactions- combination (two or more reactants produce a single product)
- single displacement
- decomposition
- gas formation
- precipitation
- What is the simplest whole number coefficient for aluminum bromide in the above reaction (#27)?
Khan Academy: Balancing Chemical Equations ; Wyzant: Reactions
- 1 (recall that bromine is diatomic, as well as the correct charges on the monatomic ions)
- 2
- 3
- 4
- none of the above
- How many moles of oxygen are required for the complete reaction of 45 g of C2H4 when it is burned?
Khan Academy: Balancing Chemical Equations , Stoichiometry ; Wyzant: Reactions , Basic Stoichiometry- 1.3 x 102 mol (balance the equation to start, then convert reactant grams to moles)
- 0.64 mol
- 112.4 mol
- 4.8 mol
- none of the above
- 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: Reactions , Stoichiometry- 0.56%
- 43.6%
- 87.1% (be sure to balance the equation and convert moles reactant to moles product)
- 56.0%
- 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