Chemistry Exam 4

What is the concentration of K+ in 0.15 M of K2S?

0.3M

Look again at the table in Part B, repeated below. Solid Concentration (M) Strength of light emitted A 0.20 Bright B 0.20 Dim C 0.20 None D 0.20 Bright The student is told that one of the four solids tested is actually barium chloride ,BaCl2. Which of the solids could be BaCl2?

A, D All ionic substances and strong acids are strong electrolytes.

Imagine that A and B are cations and X, Y, and Z are anions, and that the following reactions occur: AX(aq)+BY(aq)→no precipitate AX(aq)+BZ(aq)→precipitate Which of the following choices is insoluble? Imagine that and are cations and , and are anions, and that the following reactions occur: Which of the following choices is insoluble? AX AY AZ BX BY BZ

AZ

Enter the net ionic equation for the reaction of aqueous sodium chloride with aqueous silver nitrate.

Ag+(aq)+Cl−(aq)→AgCl(s) S

A student tests four solids for their ability to complete an electrical circuit when dissolved in water by observing their ability to close a circuit containing a light bulb and obtains the following results: Solid Concentration (M) Strength of light emitted A 0.20 Bright B 0.20 Dim C 0.20 None D 0.20 Bright Which of the solids is a weak electrolyte when dissolved in water?

B Molecular compounds that are weak acids or weak bases are weak electrolytes. They dissociate into component ions incompletely in water. For example, ammonia is a weak electrolyte.

Precipitation Reactions

Here are some general solubility rules: 1. Compounds of group I ions are soluble. 2. Nitrates and chlorates are soluble. 3. Except for the compounds covered by rule 1, carbonates, hydroxides, phosphates, and sulfides are insoluble.

Ion Concentration

Ion concentration refers to the molar concentration of an ion in solution. It may be identical to, or greater or less than, the molar concentration of the compound containing the ion that was used to make the solution. For soluble salts, the molarity of a particular ion is equal to the molarity of that compound times the subscript for that ion. For example, 1 M of AlCl3 is 1 M in Al3+ and 3 M in Cl−. 1 M of (NH4)2SO4 is 2 M in NH4+ and 1 M in SO42−

Insoluble sulfide compounds are generally black in color. Which of the following combinations could yield a black precipitate? Check all that apply. Na2S(aq)+KCl(aq) Li2S(aq)+Pb(NO3)2(aq) Pb(ClO3)2(aq)+NaNO3(aq) AgNO3(aq)+KCl(aq) K2S(aq)+Sn(NO3)4(aq)

Li2S(aq)+Pb(NO3)2(aq) K2S(aq)+Sn(NO3)4(aq)

The student is now told that the four solids, in no particular order, are barium chloride (BaCl2), sugar (C6H12O6), butanoic acid (C3H7COOH), and potassium bromide (KBr). Assuming that conductivity is correlated to the number of ions in solution, rank the four substances based on how well a 0.20 M solution in water will conduct electricity. Rank from most conductive to least conductive. To rank items as equivalent, overlap them. HelpReset

Most Conductive to Least COnductive Barium chloride potassium bromide butanoic acid sugar

CHeck off the samples that will conduct electricity Sugar solution Solid sugar NaCl solution Solid NaCl

NaCl solution

Classify these compounds as soluble or insoluble.

SOLUBLE strontium hydroxide sodium sulfate calcium hydroxide potassium sulfate nickel(II) sulfate potassium hydroxide iron(II) sulfate INSOLUBLE strontium sulfate copper(II) hydroxide magnesium sulfide

Classify each of these soluble solutes as a strong electrolyte, a weak electrolyte, or a nonelectrolyte. Solutes-- Formula Hydrochloric acid-- HCl Calcium hydroxide-- Ca(OH)2 Acetic acid-- H3CCOOH Ammonia-- NH3 Aluminum chloride-- AlCl3 Butanol-- C4H9OH Sucrose-- C12H22O11

STRONG hydrochloric acid calcium hydroxide aluminum chloride WEAK ammonia acetic acid NON sucrose butanol

Each of the following reactions shows a solute dissolved in water. Classify each solute as a strong electrolyte, a weak electrolyte, or a nonelectrolyte. X(s)→X(aq) CD(aq)⇌C+(aq)+D−(aq) YZ(s)→Y+(aq)+Z−(aq) PQ(aq)→P+(aq)+Q−(aq) R(l)→R(aq)

STRONG ELECTROLYTE YZ, PQ NON-ELECTROLYTE CD WEAK ELECTROLYTE X, R

Electrolytes

if a solute produces electrolytes when dissolved, it is called an electrolyte becasue the resulting ions in solution will allow the solution to conduct electricity. A solute that completely dissociates into ions is a stronger electrolyte than one that only partially dissociates into ions. If a solute remains as a molecule when dissolved, it is called a nonelectrolyte.

A scientist wants to make a solution of tribasic sodium phosphate, Na3PO4, for a laboratory experiment. How many grams of Na3PO4 will be needed to produce 700. mL of a solution that has a concentration of Na+ ions of 0.800 M ?

mass of Na3PO4 = 30.6gif