CHM 111 Lecture Notes - Lecture 12: Barium Nitrate, Chemical Equation, Ionic Compound

The Behavior of Substances in Water

Part 1:

1. Ammonia, NH₃, is a weak electrolyte. It forms ions in solution by reacting with water molecules to form the ammonium ion and hydroxide ion. Write the balanced chemical reaction for this process, including state symbols.
2. From everyday experience, you are probably aware that table sugar (sucrose), C₁₂H₂₂O₁₁, is soluble in water. When sucrose dissolves in water, it doesn’t form ions through any reaction with water. It just dissolves without forming ions, so it is a nonelectrolyte. Write the chemical equation for the dissolving of sucrose in water.
3. Both NH₃ and C₁₂H₂₂O₁₁ are soluble molecular compounds, yet they behave differently in an aqueous solution. Briefly explain why one is a weak electrolyte and the other is a nonelectrolyte.
4. Hydrochloric acid, HCl, is a molecular compound that is a strong electrolyte. Write the chemical reaction of HCl with water.
5. Compare the ammonia reaction with that of hydrochloric acid. Why are both of these substances considered electrolytes?
6. Explain why HCl is a strong electrolyte and ammonia is a weak electrolyte.
7. Classify each of the following substances as either ionic or molecular:

• KCl
• NH₃
• CO₂
• MgBr₂
• HCl
• Ca(OH)₂
• PbS
• HC₂H₃O₂  

8. For those compounds above that, you classified as ionic, use the solubility rules to determine which are soluble.
9. The majority of ionic substances are solids at room temperature. Describe what you would observe if you placed a soluble ionic compound and an insoluble ionic compound in separate beakers of water.
10. Write the chemical equation(s), including state symbols, for what happens when each soluble ionic compound that you identified above is placed in water. Are these substances reacting with water when they are added to water?
11. How would you classify the soluble ionic compounds: strong electrolyte, weak electrolyte, or nonelectrolyte? Explain your answer.
12. Sodium chloride, NaCl, is a strong electrolyte, as is hydroiodic acid, HI. Write the chemical equations for what happens when these substances are added to water. m
13. Are NaCl and HI strong electrolytes because they have similar behavior in an aqueous solution? If not, describe, using words and equations, the different chemical process that takes place in each case.

Part 2:

You have two hypothetical molecular compounds, AX and AY. AX is a strong electrolyte and AY is a weak electrolyte. The compounds undergo the following chemical reactions when added to water.

AX (aq) + H₂O (l) → AH₂O⁺ (aq) + X⁻ (aq)

AY (aq) + H₂O (l) → AH₂O⁺ (aq) + Y⁻ (aq)

1. Explain how the relative amounts of AX ( aq ) and AY ( aq ) would compare if you had a beaker of water with AX and a beaker of water with AY.
2. How would the relative amounts of X⁻ ( aq) and Y⁻ ( aq) in the two beakers compare? Be sure to explain your answer.

<p>1. (10)What ions and/or molecules are present in relatively large proportions in a solution of a weak acid, HF (aq)?<br />Select all appropriate answers.<br /><br /> H+<br /> HF<br /> F-<br /> HF+<br /> F+<br /> F2+<br /> H2-<br /> F2-<br /> H<br /> F<br /><br />2. (10)What ions and/or molecules are present in relatively large proportions in a solution of a strong base NaOH (aq)?<br />Select all appropriate answers. <br /><br /> NaOH<br /> Na2+<br /> OH2-<br /> OH-<br /> NaO+<br /> OH+<br /> Na<br /> Na+<br /> OH<br /><br />3. (10)What ions and/or molecules are present in relatively large proportions in a solution of a strong acid HClO3 (aq)?<br />Select all appropriate answers.<br /><br /> HClO3<br /> ClO3-<br /> HCl+<br /> Cl+<br /> H+<br /> ClO3+<br /> O3-<br /> O32-<br /> HCl<br /> None of these is present in relatively large proportions<br /><br /> 4. (10)What ions and/or molecules are present in relatively large proportions in a solution of the soluble ionic compound NiCl2 (aq)?<br /> Select all appropriate answers. <br /><br /> Ni2+<br /> NiCl2<br /> Cl22-<br /> Cl2-<br /> Ni+<br /> Cl2-<br /> Ni<br /> Cl<br /> Cl2<br /> Cl-<br /><br />5. (5)Which of the following equations represents the proper net ionic equation for the precipitation of an insoluble sulfide compound from ZnBr2(aq) and Na2S(aq).<br /><br /> Na2S(aq) + ZnBr2(aq) ----&gt; 2 NaBr(aq) + ZnS(s)<br /> Zn2+(aq) + S2-(aq) ----&gt; ZnS(s)<br /> Na2S(aq) + 2 Br-(aq) ----&gt; 2 NaBr(s) + S2-(aq)<br /> Br-(aq) + Na+(aq) ----&gt; NaBr(s)<br /> S2-(aq) + ZnBr2(aq) ----&gt; ZnS(s) + 2 Br-(aq)<br /> 3 S2-(aq) + 2 Zn3+(aq) ----&gt; Zn2S3(s)<br /> Na2+(aq) + Br2-(aq) ----&gt; Na2Br2(s)<br /> Na2S(aq) + ZnBr2(aq) ----&gt; Na2Br2(aq) + ZnS(s)<br /> Zn+(aq) + S-(aq) ----&gt; ZnS(s)<br /><br />6. (5)Which of the following equations represents the proper net ionic equation for the complete neutralization reaction between the strong acid HI(aq) and the weak base NH3(aq)?<br /><br /> H+ (aq) + NH3(aq) ----&gt; NH4+ (aq)<br /> HI (aq) + OH- (aq) ----&gt; H2O (l) + I- (aq)<br /> HI (aq) + NH3(aq) ----&gt; NH4I (aq)<br /> I- (aq) + NH4+ (aq) ----&gt; NH4I (aq)<br /> H+ (aq) + OH- (aq) ----&gt; H2O (l)<br /> HI (aq) + OH- (aq) ----&gt; H2IO (aq)<br /> H+ (aq) + NH4+ (aq) ----&gt; NH5+ (aq)<br /> I- (aq) + OH- (aq) ----&gt; HIO (aq)<br /><br />mark<br /><br /> 7. (5)What are the spectator ions in the solution after completely precipitating an insoluble carbonate compound when mixing Ca(ClO3)2 (aq) and Na2CO3 (aq)?<br /><br /> Ca2+ , ClO3- , Na+ , and CO32-<br /> Na+ and CO32-<br /> CO32- and ClO3-<br /> CO32- and Ca2+<br /> Ca2+ and ClO3-<br /> Ca2+ and Na+<br /> Na+<br /> ClO3-<br /> ClO3- and Na+<br /> Ca2+<br /><br />8. (5)What are the spectator ions in the solution after the complete neutralization reaction occurs when mixing the weak acid H2S (aq) and the strong base KOH (aq)?<br /><br /> H+ , S2- , K+ , and OH-<br /> OH- and K+<br /> H+ and OH-<br /> OH- and S2-<br /> K+ and S2-<br /> K+ and H+<br /> S2- and H+<br /> K+<br /> S2-</p>

Fill the questions according to Data Table 7-2

5. balanced formula equation: for each combination of solutions that produced new product. write correct chemical formulas for the new compounds that could form from the ions present. Indicate which of the new compunds is a precipitate. If no reaction occurs, write NR.

6. complete ionic equation: write complete ionic equations for the precipitation reactions that you observed. show the reactants as ions, the precipitate as a solid, and the spectator ions as unchanged. balance each equation for mass and change. the total charge should be zero on each side of the equation.

7. net ionic equation: write the net ionic equations for each reaction in the preceding question.