A student is provided with an unknown solution, which will contain one of the follow cations: Ba? (aq), Ca* (aq), Pb²* (aq), or K* (aq). The unknown solution is mixed with aqueous sodium chloride, sodium hydroxide, and sodium sulfate. The student's observations are shown below. NaCl (aq) NaOH (aq) Na,SO4 (aq) Unknown solution precipitate precipitate precipitate Which anion does the unknown solution contain? O Barium ion, Ba* (aq) Calcium ion, Ca²* (aq) Potassium ion, K* (aq) Lead(II) ion, Pb²* (aq)

Separate samples of a solution of an unknown soluble ionic compound are treated with KCl, Na2SO4, and NaOH. A precipitate forms only when Na2SO4 is added. Which cations could be present in the unknown soluble ionic compound?

The Behavior of Substances in Water Part 1: a 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. b From everyday experience you are probably aware that table sugar (sucrose), C12H22O11, is soluble in water. When sucrose dissolves in water, it doesnt 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. c Both NH3 and C12H22O11 are soluble molecular compounds, yet they behave differently in aqueous solution. Briefly explain why one is a weak electrolyte and the other is a nonelectrolyte. d Hydrochloric acid, HCl, is a molecular compound that is a strong electrolyte. Write the chemical reaction of HCl with water. e Compare the ammonia reaction with that of hydrochloric acid. Why are both of these substances considered electrolytes? f Explain why HCl is a strong electrolyte and ammonia is a weak electrolyte. g Classify each of the following substances as either ionic or molecular. KCl NH3 CO2 MgBr2 HCl Ca(OH)2 PbS HC2H3O2 h For those compounds above that you classified as ionic, use the solubility rules to determine which are soluble. i 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. j 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? k How would you classify the soluble ionic compounds: strong electrolyte, weak electrolyte, or nonelectrolyte? Explain your answer. l 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 Are NaCl and HI strong electrolytes because they have similar behavior in 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) a 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. b How would the relative amounts of X(aq) and Y(aq) in the two beakers compare? Be sure to explain your answer.

A student is asked to identify the metal nitrate present in an aqueous solution. The cation in the solution can be either Na+, Ba2+, Ag+, or Ni2+. Results of solubility experiments are as follows: unknown + chloride ions—no precipitate unknown + carbonate ions—precipitate unknown + sulfate ions—precipitate What is the cation in the solution?