Chem 4 - Sample Exam #2

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1. Complete the following statements:

The total number of atoms present before and after a chemical reaction takes place must be _______________________.

Name and write the formula for three strong acids that are used frequently in the laboratory

_____________________ _____________________ _____________________

Name and write the formula for two bases that are used frequently in the laboratory

_____________________ _____________________

When an ionic compound dissolves, the solution contains ____________ and is an electrolyte.

2. Write the correct formula for each of the following compounds:

potassium hydroxide _________________________________

sodium carbonate _________________________________

nitric acid _________________________________

cobalt(III) nitrate _________________________________

calcium chloride _________________________________

lead(IV) oxide _________________________________

dinitrogen pentoxide _________________________________

ammonium chromate _________________________________

iron(II) chloride _________________________________

barium sulfate _________________________________

3. When you combine Na metal with water, there is a reaction. One of the products is a gas and the other is NaOH. Write the balanced equation. What is the gas? ______________________.

4. Answer the following True/False questions:

___ T ___ F A weak acid is one that does not ionize very well

___ T ___ F Since NaCl is ionic, it always conducts electricity, whether solid or in solution

___ T ___ F All compounds containing the S^2- ion are insoluble in water

___ T ___ F Every reaction that undergoes oxidation uses oxygen as the oxidizing agent

___ T ___ F When an atom gains electrons, it is reduced and becomes an anion

___ T ___ F When Zinc reacts with HCl, Cl₂ and H₂ gases are produced

___ T ___ F For both CH₄ and CO₂, carbon has a valence of -4

___ T ___ F Combustion reactions always product water and carbon monoxide

___ T ___ F A decomposition reaction is the formation of water from H₂ and O₂

___ T ___ F The reaction between H⁺ and OH^- is often called an acid-base reaction

___ T ___ F The ionic compound produced from an acid-base reaction is a salt

___ T ___ F The mass percentage of hydrogen in water is 100%

___ T ___ F The empirical formula is always different from the actual formula

___ T ___ F For this reaction C + O₂ --> CO₂, 1 gram of C reacts with exactly 1 gram O₂

___ T ___ F Spectator ions love to watch Monday Night Football, and root for the home team

5. List 4 ways you can determine if a chemical reaction has occurred.

_________________________________ _________________________________

_________________________________ _________________________________

6. Show the products and balance the following reactions. Then, write the complete and net ionic equations for each.

Ca(NO₃)₂ (aq) + H₂SO₄ (aq) -->

Na₂CO₃ (aq) + CoCl₂ (aq) -->

7. Balance the following equations. If products are not shown, write the correct formulas yourself, and then balance the equation.

SiO₂ + HF --> SiF₄ + H₂O

Co + O₂ --> Co₂O₃

NH₃ + O₂ --> NO + H₂O

FeCl₃ + KOH -->

H₂ + N₂ -->

8. Write the balanced equation for the combustion (oxidation) of propane (C₃H₈) with O₂.

9. The percentage composition of a new compound is 40% sulfur and 60% oxygen. What is its empirical formula? If this compound has molar mass of 160 grams. What is its actual formula?

10. Calculate the number of moles in 42.5 g phenol (C₆H₆O).

11. What is the molar mass of:

CH₄ _________________________

potassium sulfate ____________________

AgI _________________________

sodium hydroxide ____________________

CO₂ _________________________

sulfuric acid _______________________

12. Show the complete electron configuration for following elements (e.g. N = 1s² 2s² 2p³)

Ne = ______________________________________________

Li = ______________________________________________

Br = ______________________________________________

Cs = ______________________________________________

13. You react Al with O₂ to produce Al₂O₃. You start with 10 grams of Al and 20 grams of O₂. Which reactant is limiting? __________________ Based on the limiting reactant, how many grams of Al₂O₃ will you produce?

14. How many electrons (2n² ) will be in each of the first three principal energy levels? Show the names for the different electron orbitals present in each energy level.

	# Subshells	Maximum # Electrons	Names of orbitals present
n =1
n = 2
n = 3

EXTRA CREDIT (4 points): Do all oxidation reactions require oxygen? ____ Yes ____ No

Write an equation for the oxidation of Mg with O₂. Show the reaction that occurs when you add this product to water. (These reactions were performed in the lab.)

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