Aqueous Reactions Chapter 4 Aqueous Reactions and Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO  2006, Prentice Hall, Inc. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten

Aqueous Reactions Solutions: Homogeneous mixtures of two or more pure substances. The _____ is present in greatest abundance. All other substances are _____.

Aqueous Reactions Dissociation When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them. This process is called _____.

Aqueous Reactions Electrolytes Substances that dissociate into ions when dissolved in water. Example: A _____ may dissolve in water, but it does not dissociate into ions when it does so. Example:

Aqueous Reactions Electrolytes and Nonelectrolytes _______________ _______________ tend to be electrolytes.

Aqueous Reactions Electrolytes and Nonelectrolytes ________________ tend to be nonelectrolytes, except for _____ and _____.

Aqueous Reactions SAMPLE EXERCISE 4.1 Relating Relative Numbers of Anions and Cations to Chemical Formulas The diagram below represents an aqueous solution of one of the following compounds: MgCl 2, KCl, or K 2 SO 4. Which solution does it best represent?

Aqueous Reactions Electrolytes A strong electrolyte dissociates __________________ __________________ A weak electrolyte only dissociates __________________ __________________

Aqueous Reactions Strong Electrolytes Are… Strong acids Strong bases Soluble ionic salts

Aqueous Reactions Precipitation Reactions When one mixes ions that form compounds that are insoluble (as could be predicted by the solubility guidelines), a precipitate is formed.

Aqueous Reactions Metathesis (Exchange) Reactions a.k.a. Double Replacement Rxns Metathesis comes from a Greek word that means ______________ AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

Aqueous Reactions Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means __________ It appears the ions in the reactant compounds __________________________ AgNO 3 (aq) + KCl (aq) 

Aqueous Reactions AgNO3 (aq) + KCl (aq)  How did we know that silver chloride was a solid??? We checked the ____________________.

Aqueous Reactions

Aqueous Reactions Predict the products of the following reactions BaCl 2 (aq) + K 2 SO 4 (aq) Fe 2 (SO 4 ) 3 (aq) + LiOH (aq) Mg(NO 3 ) 2 (aq) + CaS (aq) NaCl (aq) + KNO 3 (aq)

Aqueous Reactions Solution Chemistry It is helpful to pay attention to exactly what species are present in a reaction mixture (i.e., solid, liquid, gas, aqueous solution). If we are to understand reactivity, we must be aware of just what is changing during the course of a reaction.

Aqueous Reactions Molecular Equation The _______________ equation lists the reactants and products in their molecular form. AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

Aqueous Reactions Ionic Equation In the ionic equation all __________________ (strong acids, strong bases, and soluble ionic salts) are _______________ into their ___________. This _______________ reflects the species that are found in the reaction mixture. Ag + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq)  AgCl (s) + K + (aq) + NO 3 - (aq)

Aqueous Reactions Net Ionic Equation To form the _____ ionic equation, __________ anything that does not change from the left side of the equation to the right. Ag + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq)  AgCl (s) + K + (aq) + NO 3 - (aq)

Aqueous Reactions Net Ionic Equation To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. The only things left in the equation are _______________________ (i.e., react) during the course of the reaction. Ag + (aq) + Cl - (aq)  AgCl (s)

Aqueous Reactions Net Ionic Equation To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. The only things left in the equation are those things that change (i.e., react) during the course of the reaction. Those things that didn’t change (and were deleted from the net ionic equation) are called ___________. Ag + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq)  AgCl (s) + K + (aq) + NO 3 - (aq)

Aqueous Reactions Writing Net Ionic Equations 1.Write a 2.Dissociate all 3.Cross out anything that remains unchanged from the left side to the right side of the equation. 4.Write the net ionic equation with the species that remain.

Aqueous Reactions Writing Net Ionic Equations Write the net ionic equation for each reaction Pb(NO 3 ) 2 (aq) + KI (aq) Li 2 S (aq) + BaBr 2 (aq) NH 4 Cl (aq) + Sr(OH) 2 (aq)

Aqueous Reactions Acids: Substances that increase the concentration of H + when dissolved in water (__________). Proton donors (________________).

Aqueous Reactions Acids There are only seven strong acids: Hydrochloric (HCl) Hydrobromic (HBr) Hydroiodic (HI) Nitric (HNO 3 ) Sulfuric (H 2 SO 4 ) Chloric (HClO 3 ) Perchloric (HClO 4 )

Aqueous Reactions Bases: Substances that increase the concentration of OH − when dissolved in water (________). Proton acceptors (______________).

Aqueous Reactions Bases The strong bases are the soluble salts of hydroxide ion:

Aqueous Reactions Acid-Base Reactions In an acid-base reaction, _____ donates a proton (H + ) to the _____.

Aqueous Reactions Neutralization Reactions Generally, when solutions of an acid and a base are combined, the products are ____________________. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)

Aqueous Reactions Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l )

Aqueous Reactions Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l ) H + ( aq ) + Cl - (aq) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l ) H+ (aq) + OH- (aq) → H2O (l)

Aqueous Reactions Neutralization Reactions What does this have to do with you??? What happens when you have a stomach ache? What do you do about it? Why?

Aqueous Reactions Neutralization Reactions What does this have to do with you??? Many antacids contain magnesium hydroxide. It undergoes a neutralization reaction with stomach acid. What acid constitutes the largest quantity of stomach acid? Write a net ionic equation for the neutralization reaction between magnesium hydroxide and hydrochloric acid. Mg(OH) 2 (s) + H + (aq) → Mg 2+ (aq) + H 2 O (l)

Aqueous Reactions Neutralization Reactions Observe the reaction between Milk of Magnesia, Mg(OH) 2, and HCl. Can you overdoes on antacid?? What do you think would happen?

Aqueous Reactions Gas-Forming Reactions These metathesis reactions do not give the _______________________. The __________________ decomposes to give a gaseous product ( ). CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) NaHCO 3 (aq) + HBr (aq)  NaBr (aq) + CO 2 (g) + H 2 O (l) SrSO 3 (s) + 2 HI (aq)  SrI 2 (aq) + SO 2 (g) + H 2 O (l)

Aqueous Reactions Gas-Forming Reactions This reaction gives the predicted product, but you had better carry it out in the hood, or you will be very unpopular! Just as in the previous examples, a gas is formed as a product of this reaction: Na 2 S (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 S (g)

Aqueous Reactions A Carbonated Beverage is Another Example How is a beverage carbonated? What happens to the dissolved gas? H 2 O (l) + CO 2 (g) ↔ H 2 CO 3 (aq) H 2 O (l) + CO 2 (g) ↔ 2H + (aq) + CO 3 -2 (aq)

Aqueous Reactions Oxidation-Reduction Reactions An _______ occurs when an atom or ion loses electrons. A _______ occurs when an atom or ion gains electrons.

Aqueous Reactions Oxidation-Reduction Reactions

Aqueous Reactions Oxidation Numbers To determine if an oxidation-reduction reaction has occurred, we assign an _________________ to each element in a neutral compound or charged entity.

Aqueous Reactions Oxidation Numbers Elements in their elemental form have an oxidation number of _____. The oxidation number of a monatomic ion is ___________________.

Aqueous Reactions Oxidation Numbers Nonmetals tend to have negative oxidation numbers, ________________________________ ______________________________.  Oxygen has an oxidation number of −2, except in the peroxide ion in which it has an oxidation number of −1.  Hydrogen is −1 when bonded to a metal, +1 when bonded to a nonmetal.

Aqueous Reactions Oxidation Numbers Nonmetals tend to have negative oxidation numbers, although some are positive in certain compounds or ions.  Fluorine always has an oxidation number of −1.  The other halogens have an oxidation number of −1 when they are negative; they can have positive oxidation numbers, however, most notably in oxyanions.

Aqueous Reactions Oxidation Numbers The sum of the oxidation numbers in a neutral compound is 0. The sum of the oxidation numbers in a polyatomic ion is the _________________.

Aqueous Reactions Oxidation Numbers Find the oxidation numbers for each of the following species. CO 3 2- H 2 S S 8 SCl 2 SO 4 2- Cr 2 O 7 2-

Aqueous Reactions Displacement Reactions In displacement reactions, ions ________________. The ions, then, are reduced.

Aqueous Reactions Displacement Reactions In this reaction, silver ions ________ copper metal. Cu (s) + 2 Ag + (aq)  Cu 2+ (aq) + 2 Ag (s)

Aqueous Reactions Displacement Reactions The reverse reaction, however, does not occur. Cu 2+ (aq) + 2 Ag (s)  Cu (s) + 2 Ag + (aq) x

Aqueous Reactions Activity Series

Aqueous Reactions Use the Activity Series to predict the products of the following reactions. If the reactions does take place, write the net ionic equation for the reaction. Lastly, identify the species being oxidized and reduced. Al (s) + HBr (aq) Fe (s) + KI (aq) Zn (s) + Ni(NO 3 ) 2 (aq)

Aqueous Reactions Molarity Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Molarity is one way to measure the __________________________________.

Aqueous Reactions Mixing a Solution How many grams of silver nitrate are required to make 100 mL of a 0.5 M solution? How many grams of NaOH are required to make 50 mL of an 8.2 M solution?

Aqueous Reactions Dilution

Aqueous Reactions Dilution You have 1L of a 1.00 M stock solution of hydrochloric acid. You need to make 500 mL of a 0.20M solution. How much of the stock solution is needed? You need to make 100 mL of 0.50 M nitric acid. The storage bottle reads 6.0M. How much of the 6.0M nitric acid will you need?

Aqueous Reactions Using Molarities in Stoichiometric Calculations How many grams of Ca(OH) 2 are needed to neutralize 20.0 mL of a M H 2 SO 4 solution?

Aqueous Reactions Using Molarities in Stoichiometric Calculations How many liters of M HCl are needed to react completely with mol Pb(NO 3 ) 2, forming the precipitate PbCl 2 ?

Aqueous Reactions Titration The _____________ technique in which one can calculate the ________________ ________________ ________________.

Aqueous Reactions Titration

Aqueous Reactions Titration Example A g sample of impure oxalic acid (H 2 C 2 O 4 ) is dissolved in water and an acid-base indicator is added. The sample required mL of M NaOH to reach the equivalence point. What is the mass of oxalic acid and what is its mass percent in the sample?

Aqueous Reactions Titration A g sample of sodium carbonate, a base, requires mL of aqueous HCl for titration to the equivalence point. What is the molarity of the HCl?