Reactions in Aqueous Solutions and Stiochiometry Chapter 4

Objectives 2.0 Define key terms and concepts. 2.7 Balance chemical equations. 2.8 Predict the products for basic chemical reactions. 2.9 Predict if a precipitate will form in a reaction. 2.10 Write the net ionic equation for a reaction.

Objectives 2.11 Identify the stoichiometric relationship between chemicals using a chemical reaction. 2.12 Calculate theoretical yield using stoichiometry. 2.13 Determine the limiting reagent in a reaction. 2.14 Calculate the percent yield for a reaction. 2.15 Determine the amount of a compound present in solution by using gravimetric or volumetric analysis.

Chemical Reactions and Chemical Equations Process by which a substance is changed into one or more new substances Chemical Equation Uses chemical symbols to show what occurs during a chemical reaction Must be balanced

Chemical Equations Reactants products yields

Chemical Equations

Tricks to Balancing the Equations If an element is present in two different compounds on both sides of the reaction, balance that element first. Treat polyatomic ions as one unit If –OH is present on the reactant side and water on the product side, balance water as H-OH. Balance lone elements or diatomic elements last

Balance the Following Equations Al + O2 → Al2O3 SnO2 + H2 → Sn + H2O C2H6 + O2 → CO2 + H2O H2SO4 + LiOH  H2O + Li2SO4

The reaction of potassium permanganate with hydrochloric acid yeilds potassium chloride, manganese (II) chloride, water, and chlorine gas. Write the balanaced chemical equation for this reaction.

When calcium hydroxide reacts with phosphoric acid, water and calcium phosphate are produced. Write the chemical equation for this reaction.

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Types of Reactions

Complete and balance the following reactions. MgO  Ba + HNO3  Cu2O  C3H8 + O2 

Complete and balance the following reactions. Zn(NO3)2 + AgI  CaCl2 x 2H2O + heat  AgNO3 + Na3PO4  C10H22 + O2 

Types of Reactions Precipitation When an insoluble solid forms during a reaction Can determine precipitate using solubility rules

Solubility Rules Soluble Compounds Almost all salts of Na+, K+, and NH4+ Salts of NO3-, ClO3-, ClO4-, C2H3O2- Exceptions Almost all salts of Cl-, Br-, I- Halides of Ag+, Hg2+, Pb2+ Compounds containing F- Fluorides of Mg2+, Ca2+, Sr2+, Ba2+, and Pb2+ Salts of SO42- Sulfates of Ca2+, Sr2+, Ba2+, Pb2+ Insoluble Compounds Most salts of CO32-, PO43-, C2O42-, CrO42- Salts of NH4+ and alkali metal cations Most metal sulfides, S2- Most metal hydroxides and oxides

Net Ionic Equations

Write the net ionic equation for the following reaction Pb(NO3)2 + KI 

Write the net ionic equation for the following reaction Ba(NO3)2 + MgSO4 →

Write the net ionic equation for the following reaction NaOH + H2SO4 

Write the net ionic equation for the following reaction HC2H3O2 + NaHCO3 

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Acid-Base Reactions Acids Have a sour taste Will turn litmus paper red Will conduct electricity when in aqueous solution Reacts with metals such as Zn, Mg, and Fe to produce hydrogen gas 2HCl(aq) + Zn(s)  ZnCl2(aq) + H2(g) Will react with carbonates and bicarbonates to produce CO2 2HCl(aq) + CaCO3(s)  CaCl2(aq) + H2O(l) + CO2(g)

Acid-Base Reactions Strong Acids Weak Acids Will completely ionize in water H2SO4  H+ + HSO4- Only a few strong acids HCl, HNO3, H2SO4, HBr, HI, HClO4 Weak Acids Will only partially ionize in water Most acids are weak HF, acetic acid, citric acid

Acid-Base Reactions Bases Have a bitter taste Feel Slippery Turns litmus paper Blue Will conduct electricity when in aqueous solution

Acid-Base Reactions Strong Bases Weak Bases Will completely ionize in water NaOH  Na+ + OH- The hydroxides of Group I & II metals are considered to be strong bases Weak Bases Weak Bases do not furnish OH- ions by dissociation. Instead, they react with water to generate OH- ions. NH3 + H2O  NH4 + OH-

Acid-Base Reactions Neutralization Salt The reaction between a strong acid and a strong base with produces salt and water Double replacement reaction Salt An ionic compound that does not have H+ or OH- ions

Complete the following neutralization reactions Complete the following neutralization reactions. H2SO4 + KOH  H3PO4 + Mg(OH)2  HNO3 + Ca(OH)2 

NaHCO3 + HNO3  NaNO3 + H2O + CO2 Acid-Base Reactions Some acid-base reactions will also produce a gas. These usually involve a carbonate, bicarbonate, sulfite, or sulfide Na2CO3 + 2HCl  2NaCl + H2CO3 NaHCO3 + HNO3  NaNO3 + H2O + CO2 K2S + 2HBr  2KBr + H2S

Redox Reactions Involve the gain and lose of electrons by chemicals in a reaction Oxidation Reaction Loss of an electron Reducing Agent Provides Electrons (is oxidized) Reduction Reaction Gain of an electron Oxidizing Agent Accepts Electrons (is reduced)

Redox Reactions LEO the lion goes GER Lose Electrons – Oxidation Gain Electrons – Reduction H2 + F2 → 2HF Oxidation Reaction: H2 → 2H+ + 2e- Reduction Reaction: F2 + 2e- → 2F-

Identify what is being oxidized and reduced in the following reactions. H2 + O2  H2O Fe + CuSO4  FeSO4 + Cu Fe + S8  FeS Mg + HCl  MgCl2 + H2

Redox Reactions Combination Reactions 2H2(g) + O2(g)  2H2O(l) Decomposition Reactions 2H2O(l)  2H2(g) + O2(g) 2HgO(s) + heat  2Hg(l) + O2(g) Combustion Reactions 2C4H10(g) + 13O2(g)  8CO2(g) + 10H2O(l) + heat

Redox Reactions Displacement Reactions Hydrogen Displacement Mg(s) + HCl(aq)  MgCl2(aq) + H2(g) Metal Displacement Cu + AgCl  CuCl2(aq) + Ag(s) Halogen Displacement Cl2(g) + 2KBr(aq)  2KCl(aq) + Br2(l) Disproportion Reaction 2H2O2(aq)  2H2O(l) + O2(g)

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Stoichiometry The quantitative study of reactants and products in a chemical reaction. Can relate moles of one compound to moles of another compound using a chemical equation to determine Theoretical Yield, or how much product you would expect to produce.

Stoichiometry Mass of Compound A Moles of Compound A Mass of A ÷ Molar Mass of A Use chemical equation to determine molar relationship Mass of Compound B Moles of Compound B Moles of B x Molar Mass of B

Al + O2 → Al2O3 2.6 moles of aluminum reacts with oxygen gas to produce aluminum oxide. How many moles of aluminum oxide are produced?

H3PO4 + Mg(OH)2  Mg3(PO4)2 + H2O 6.5g of phosphoric acid reacts with magnesium hydroxide to produce magnesium phosphate and water. How many moles of water are produced?

Oxygen gas and hydrofluoric acid are produced when fluorine gas is reacted with water. F2(g) + H2O(l)  HF(g) + O2(g) If 24.8g of fluorine gas are reacted with excess water, how many grams of oxygen can be produce?

Limiting Reagents Limiting Reagents Excess Reagents The reactant that is used up first in the reaction Determines the amount of product that will be produced. Excess Reagents Will not be fully used up during the reaction because it is present in excess of the limiting reagent

H3PO4 + Mg(OH)2  Mg3(PO4)2 + H2O What is the limiting reagent? If 12.6g of phosphoric acid are reacted with 25.3 g of magnesium hydroxide in the following reaction: H3PO4 + Mg(OH)2  Mg3(PO4)2 + H2O What is the limiting reagent?

AgNO3 (aq) + H2SO4 (aq) → Ag2SO4 (s) + HNO3 (aq) If 18.6g of AgNO3 is reacted with 3.6 moles of H2SO4 in the following reaction: AgNO3 (aq) + H2SO4 (aq) → Ag2SO4 (s) + HNO3 (aq) How many grams of silver sulfate will be produced?

If 2. 3 grams of silver nitrate are reacted with 6 If 2.3 grams of silver nitrate are reacted with 6.9g of sulfuric acid according to the following reaction, AgNO3 (aq) + H2SO4 (aq) → Ag2SO4 (s) + HNO3 (aq) How many grams of silver sulfate are produced?

Reaction Yield Actual Yield The amount of chemical actually obtained from the reaction Actual Yield Theoretical Yield Percent Yield = x 100

What is the percent yield for the synthesis of aluminum oxide if you calculate the theoretical yield to be 13.6g but you produce 10.5g experimentally?

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Gravimetric Analysis An analytical technique based on the measurement of mass. A sample of unknown composition is reacted with another compound to form a precipitate. The ion you want to analyze for is the limiting reagent in the reaction. The precipitate is then filtered, dried and massed. This information is used to calculate the amount of ion(s) present in the initial compound. Very accurate, but only works well for reactions that produce 100% yield.

Gravimetric Analysis

An excess of Na2SO4 is added to a solution containing soluble barium ion to produce BaSO4. How many grams of barium ion are present in the solution if 565mg of BaSO4 was produced?

An excess of HCl is added to a solution containing silver ion to produce AgCl. How many grams of silver ion are present in the solution if 1.6g of AgCl was produced?

25mL of lead (II) nitrate solution of an unknown concentration was reacted with rubidium arsenate, Rb3AsO4. After filtering and drying, 0.0814g of precipitate was formed. What was the concentration of lead (II) nitrate in the solution?

A 1.25L sample of river water was analyzed for Pb2+ ions by adding excess Na2SO4. If 231.6mg of PbSO4 is produced, what is the concentration of Pb ion in the water?

Acid-Base Titrations Titration Volumetric Analysis Indicators Addition of a solution of a known concentration (standard solution) to a solution of unknown concentration until the reaction is complete (reaches its equivalence point) Volumetric Analysis Indicators Utilized during titration to determine when the reaction is complete.

Acid-Base Titrations Indicator pH Range Thymol blue 1.2 red 2.8 yellow 8.0 9.6 blue Methyl orange 3.1 4.4 yellow/orange Bromocresol green 3.8 5.4 Methyl red 6.2 Phenolphthalein colorless 9.8 pink

How many mL of 0. 45M NaOH are needed to neutralize 50mL of a 0 How many mL of 0.45M NaOH are needed to neutralize 50mL of a 0.125M solution of HCl?

What is the concentration of a HNO3 solution if 32mL reacts with 42 What is the concentration of a HNO3 solution if 32mL reacts with 42.4mL if 0.150M Mg(OH)2 in the following reaction? HNO3(aq) + Mg(OH)2(aq)  Mg(NO3)2(aq) + H2O(l)

What volume of 0. 25M HNO3 reacts with 42. 4mL if 0 What volume of 0.25M HNO3 reacts with 42.4mL if 0.150M Na2CO3 in the following reaction? 2HNO3(aq) + Na2CO3(aq)  2NaNO3(aq) + H2O(l) + CO2(g)

What volume of 0. 30M acetic acid will react with 40. 5mL if 0 What volume of 0.30M acetic acid will react with 40.5mL if 0.275M sodium bicarbonate? What is the balanced chemical equation for this reaction?

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