One way the U.S. Environmental Protection Agency (EPA) tests for chloride contaminants in water is by titrating a sample of silver nitrate solution. Any chloride anions in solution will combine with the silver cations to produce bright white silver chloride precipitate. Suppose an EPA chemist tests a 250. mL sample of groundwater known to be contaminated with cadmium chloride, which would react with silver nitrate solution like this: 2 AgCl(s) + Cd(NO),(aq) CdCl2(aq) + 2 AgNO3(aq) 2 AgCl(s) + Cd( The chemist adds 24.0 mM silver nitrate solution to the sample until silver chloride stops forming. He then washes, dries, and weighs the precipitate. He finds he has collected 5.5 mg of silver chloride. Calculate the concentration of cadmium chloride contaminant in the original groundwater sample. Round your answer to 2 significant digits. mg L G

A 1.345-g sample of a compound of barium and oxygen was dissolved in hydrochloric acid to give a solution of barium ion, which was then precipitated with an excess of potassium chromate to give 2.012 g of barium chromate, BaCrO4. What is the formula of the 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.

Arsenic acid, H3AsO4, is a poisonous acid that has been used in the treatment of wood to prevent insect damage. Arsenic acid has three acidic protons. Say you take a 25.00-mL sample of arsenic acid and prepare it for titration with NaOH by adding 25.00 mL of water. The complete neutralization of this solution requires the addition of 53.07 mL of 0.6441 M NaOH solution. Write the balanced chemical reaction for the titration, and calculate the molarity of the arsenic acid sample.

One method for determining the purity of aspirin (C9H8O4) is to hydrolyze it with NaOH solution and then to titrate the remaining NaOH. The reaction of aspirin with NaOH is as follows: A sample of aspirin with a mass of 1.427 g was boiled in 50.00 mL of 0.500 M NaOH. After the solution was cooled, it took 31.92 mL of 0.289 M HCl to titrate the excess NaOH. Calculate the purity of the aspirin. What indicator should be used for this titration? Why?

A 25.0-mL sample of sodium sulfate solution was analyzed by adding an excess of barium chloride solution to produce barium sulfate crystals, which were filtered from the solution. Na2SO4(aq)+BaCl2(aq)2NaCl(aq)+BaSO4(s) If 5.719 g of barium sulfate was obtained, what was the molarity of the original Na2SO4 solution?

Consider the following generic equation: H+(aq)+ B(aq)HB(aq)For which of the following pairs would this be the correct prototype equation for the acid-base reaction in solution? If it is not correct, write the proper equation for the acid-base reaction between the pair. (a) nitric acid and calcium hydroxide (b) hydrochloric acid and CH3NH2 (c) hydrobromic acid and aqueous ammonia (d) perchloric acid and barium hydroxide (e) sodium hydroxide and nitrous acid