Chem 4 - Sample Exam #4

Sample Exams are designed to give you an idea of the types of questions you can expect.  Exam numbers may not exactly agree with currently assigned material, so you may need to examine other sample exams to see questions that might be on the upcoming exam.

1. You neutralize 125 mL of acetic acid with 175 mL of 0.165 M NaOH. From these data, what is the molarity of acid in your 125-mL sample? How many moles of NaOH were used to perform this neutralization?

2. Answer the following True/False questions:

___ T ___ F A strong 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 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, Zn gets oxidized

___ T ___ F Combustion reactions are always oxidation-reduction reactions

___ 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 Spectator ions, although not involved in the reaction, are important

___ T ___ F Fe(OH)₃ is a strong base, because it contains the OH^- ion

8 3. The system N₂(g) + 3 H₂(g) --> 2NH₃(g) is at equilibrium. Use Le Chatelier's Principle to predict the direction in which the equilibrium will shift (forward, reverse, or no change) for the following :

[NH₃] increased _______________________ [N₂] increased _______________________

[H₂] decreased _______________________ everything doubled _______________________

4. Based on the activity series, predict whether the following reactions will occur. Show the products. If reaction does not occur as shown, write "No Reaction" for the products.

Zn + CuSO₄ -->

Ag + CuSO₄ -->

Cu + AgNO₃ -->

Zn + Mg(NO₃)₂ -->

8 5. For each of the following oxidation-reduction reactions, (a) balance the chemical equation, (b) identify the element oxidized and which is reduced, (c) show the total number of electrons lost and total number of elctrons gained.

O₂+ F₂ --> OF₂

Element oxidized: _______ Element reduced: _______

Total electrons lost: _______ gained __________

Mg + Cl₂ --> MgCl₂

Element oxidized: _______ Element reduced: _______

Total electrons lost: _______ gained ___________

6. Based on the following oxidation-reduction reaction:  MnO₄^- + Fe²⁺ --> Mn²⁺+ Fe³⁺

write the two half reactions (one for Mn and another for Fe). Remember to balance oxygens by adding water, balance hydrogens by adding H⁺, and balance charge on each side by adding electrons. Electrons gained must equal electrons lost.

7. Definition the following

acid ____________________________________________________________

base ____________________________________________________________

Oxidation ____________________________________________________________

Reduction ____________________________________________________________

acid-base conjugate pair ________________________________________________

neutralization _________________________________________________________

pH ____________________________________________________________

[H⁺] ____________________________________________________________

8. Acids and bases exist as acid-base conjugate pairs. Write the correct formula for the conjugate acid of the following bases:

NO₃^- _____________________

HPO₄^2- _____________________

Cl^- _____________________

NH₃ _____________________

Now, write the conjugate base for each of the following acids:

NH₄⁺ _____________________

H₂SO₄ _____________________

H₂O _____________________

H₃O⁺ _____________________

9. Show correct formulas for  each of the following acids or bases. Then indicate whether it is a strong or weak acid or a strong or weak base.

hydrochloric acid _________________________ _________________________

sulfuric acid _________________________ _________________________

sodium hydroxide _________________________ _________________________

ammonium hydroxide _________________________ _________________________

calcium hydroxide _________________________ _________________________

10. You have a solution of NaOH which has a concentration of 0.350 M. Using a buret, you find that you need exactly 20.0 mL of this NaOH solution to completely neutralize 15.0 mL of nitric acid. What is the concentration of the acid? How many moles of NaOH and of HNO₃ did you use in this neutralization?

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