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Review of Molecular Compounds, Lewis
Diagrams, Ionic Compounds,
Electrolytes, Chemical Equations, Moles,
Stoichiometry, and Light

The topics on the exam are listed in the title of this page. The sections of this document provide a few practice exercises for each topic. They are not comprehensive and only represent typical types of questions. By attempting to answer them you should be able to identify areas where further review is required. For sections you complete easily, spend less time reviewing. For sections you struggle with, spend more time reviewing. Use the learning targets for each topic, shared elsewhere, to guide what you need to review for each topic.

If you are looking at this document online then each topic or subtopic will link to a relevant activity with further information and/or examples.

Molecular Compounds

Names and Formulas

Given a name, write a formula. Given a formula, write a name.

  1. PCl5
  2. P4O10
  3. SF6
  4. PCl3
  5. H2O
  1. trisilicon tetranitride
  2. dioxygen difluoride
  3. iodine heptafluoride
  4. arsenic triiodide
  5. carbon monoxide

Lewis Structures and 3-D Shapes

Fill in the following table by calculating the total number of valence electrons, drawing a correct Lewis structure, and giving the name of the 3-D shape.

FormulaTotal
Valence
Electrons
Structural Drawing3-D Shape

CS2
   

AlF3
   

CBr4
   

PH3
   

H2S
   

Ionic Compounds and Electrolytes

Monatomic Ions

Assign the correct ionic charge to the following elements. The first one is done for you as an example.

  1. Li+
  2. Be
  3. B
  1. N
  2. O
  3. F

Build all possible compounds from the following ions and write their names. The first one is done for you.
K+, Ca2+, Al3+, P3–, S2–, I

  1. K3P potassium phosphide
  2.  
  3.  
  4.  
  5.  
  1.   
  2.   
  3.   
  4.   

Build all possible compounds from the following ions and write their names. Remember that some ions, those made from the transition elements in groups 3 – 12, can have more than one possible charge. The name must include the charge of the ion as a roman numeral. The first one is done for you.
Fe2+ (iron(II)), Fe3+ (iron(III)), N3–, O2–, F

  1. Fe3N2 iron(II) nitride
  2.  
  3.  
  4.  
  5.  
  1.  
  2.  
  3.  
  4.  

Polyatomic Ions

Write the name of the compound given a formula or write the formula given the name. The Ions Reference will be helpful here. Remember that acids have formulas starting with the hydrogen ion (H+) like HCl orH2SO4.

  1. Fe(NO2)2
  2. Fe(NO3)3
  3. CuOH
  4. Cu(OH)2
  5. CaCO3
  6. Ni2(CO3)3
  7. NiCO3
  8. H2SO4
  1. sodium sulfate 
  2. aluminum sulfate 
  3. cobalt(II) nitrite 
  4. cobalt(III) sulfite 
  5. magnesium phosphate 
  6. chromium(III) chlorate 
  7. barium chloride 
  8. nitric acid 

Electrolytes

Answer the following questions.

  1. What makes the formula of an electrolyte different from the formula of a non-electrolyte? Give examples for the formulas of each type of compound.
  2. Why do solutions of electrolytes in water conduct electricity?

Moles: Numbers and Masses

Molar Masses

For each of the following elements or compounds calculate the mass of 1 mole of particles of that substance. Express answers in units of g/mol. Use at least five significant figures for the mass of each element when calculating molar masses.

  1. CO2
  2. Ba3(PO4)2
  1. C6H12O6
  2. AgNO3

Putting Molar Masses to Work

For each of the masses, convert to number of moles. For each quantity given in moles, convert to mass in grams. Express each answer with the correct number of significant figures.

  1. 5.9 mol CO2
  2. 3.8 × 10-3 mol Ba3(PO4)2
  1. 1200 g C6H12O6
  2. 37.98 g AgNO3




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Chemical Equations

Balancing Equations

Balance the following chemical equations.

  1.    As +    NaOH →    Na3AsO3 +    H2
  2.    KClO3 →    KCl +    O2
  3.    KClO3 →    KClO4 +    KCl
  4.    Al +    Fe2O3 →    Al2O3 +    Fe
  1.    Li2O +    H2O →    LiOH
  2.    N2O5 +    H2O →    HNO3
  3.    H2SO4 +    HI →    H2S +    I2 +    H2O
  4.    Al +    O2 →    Al2O3


Classifying Chemical Reactions

Identify the type of reaction for each of the following chemical equations. The types used are Synthesis, Decomposition, Single Replacement, Double Replacement, and Combustion.

You may also practice balancing them, if you like. For that matter, go ahead and identify the types of reaction for the equations given above.

  1.      Mg(OH)2 →      MgO +      H2O
  2.      C +      O2 →      CO
  3.      CO +      O2 →      CO2
  4.      O3 →      O2
  5.      Fe2O3 +      H2 →      Fe +      H2O
  1.      Pb(NO3)2 +      NaCl →      PbCl2 +      NaNO3
  2.      Cu +      AgNO3 →      Ag +      Cu(NO3)2
  3.      C4H10 +      O2 →      H2O +      CO2
  4.      S8 +      O2 →      SO2
  5.      Al(NO3)3 +      NaOH →      Al(OH)3 +      NaNO3

Stoichiometry with Limiting Reactants

Solve the following stoichiometry problems.

  1. Nitrogen Gas and Hydrogen Gas react to form Ammonia. (All reactants and products are gases).
    N2 + 3H2 → 2NH3
    1. If you have 1 mol of nitrogen gas and 4 mol of hydrogen gas how many moles of ammonia form? If any reactant gases are leftover give the amount of each in moles that did not react.
    2. If you want to make 25 mol of ammonia, how much nitrogen and hydrogen gas do you need in moles?
    3. If you have 3 mol of nitrogen gas and 3 mol of hydrogen gas how many moles of ammonia form? If any reactant gases are leftover give the amount of each in moles that did not react.
    4. If you have 5.7 mol of nitrogen gas and 12.9 mol of hydrogen gas how many moles of ammonia form? If any reactant gases are leftover give the amount of each in moles that did not react.
    5. You have 12 mol nitrogen and an unlimited supply of hydrogen. How much ammonia can you make (in moles)?
  2. Zinc and Hydrochloric Acid react to form Zinc Chloride and Hydrogen Gas.
    Zn + 2HClZnCl2 + H2
    1. You want to make 0.75 mol of hydrogen gas. How many grams of zinc do you need to use?
    2. You have 10 mol zinc and 15 mol hydrochloric acid. How many moles of hydrogen gas can you make? If any reactants are leftover give the amount of each in moles that did not react.
    3. You have 130.8 g of zinc and 1 mol of hydrochloric acid. How many moles of hydrogen gas can you make? If any reactants are leftover give the amount in grams of each that did not react.
  1. Benzene (C6H6) burns in oxygen to form carbon dioxide and water.
    2C6H6 + 15O2 → 12CO2 + 6H2O
    1. If you burn 2 mol of benzene how much oxygen (in moles) is required to burn all of the benzene?
    2. How many moles of carbon dioxide result from the burning of 2 mol of benzene?
    3. How many moles of water result from the burning of 78.1 g of benzene?
    4. How many grams of carbon dioxide result from the burning of 156.2 g of benzene?
  2. Elemental sulfur (S8) reacts with fluorine gas to form sulfur hexafluoride.
    S8 + 24F2 → 8SF6
    1. How many moles of fluorine gas are required to react with each mole of elemental sulfur?
    2. If you have 12 mol of fluorine gas and 2 mol elemental sulfur then how many moles of sulfur hexafluoride can you make? If any reactants are leftover give the amount of each in moles that did not react.
    3. If you have 2.4 mol of fluorine gas and 0.05 mol elemental sulfur then how many moles of sulfur hexafluoride can you make? If any reactants are leftover give the amount of each in moles that did not react.
    4. You have 128.25 g of elemental sulfur. How many grams of fluorine gas are required to react with all of the sulfur?
    5. You have 384.8 g of elemental sulfur. If you have more than enough fluorine gas to react with all of the sulfur then how many grams of sulfur hexafluoride can you make?

Light and Atoms

Answer the following questions based on your class notes. The link is to a document we did not use but which contains much the same information as your notes.

  1. Draw a simple wave and label wavelength and amplitude.
  2. Draw two waves with different frequencies. How can the drawing tell you about the frequency of the wave?
  3. Fill in the blanks with the word ‘increases’ or ‘decreases’.
    As wavelength increases, frequency __________________.
    As frequency increases, wavelength __________________.
    As frequency increases, energy per photon __________________.
    As frequency decreases, energy per photon __________________.
  4. What is meant by the ground state and excited state of an atom?
  5. An electron must gain energy to move farther away from the nucleus. According to your reading how do electrons gain energy to move to higher energy levels?
  6. Just as a ball naturally rolls downhill (and not uphill) an electron naturally falls down to lower energy levels, eventually reaching the ground state. How is the excess energy released when this happens?
  7. Why do different elements have different bright line spectrums?
  8. What are the different regions of the electromagnetic spectrum called? List them in order from longest to shortest wavelength.
  9. What are the different regions of the electromagnetic spectrum called? List them in order from largest to smallest energy.
This review was written to give students something concrete to do in order to prepare for the final exam in June 2021 for Chemistry-3.
Last updated: Jun 10, 2021       Home