unit 12-solutions & acids and bases

Chemistry Spring 2020 Sanders

Unit 12-Solutions & Acids and Bases The suggested schedule for this unit: Week of April 27th- do all of the notes and skim through the chapters in your text book Week of May 4th-finish the Choose your own adventure item, and the Unit 12 Review either in your notebook or online

Mandatory Items: Suggested date for completion and turn in is Monday, April 27th

To be turned in to Sanders

Notes and problems 12.1





Unit 12 Review Red notebook or digital x

Choose your own adventure-Pick 1 of the following items x Chapter 14 and Chapter 18 Questions-textbook

# 1-36 odds (answers in the back of the book)

Study Guide: chapter 14 and chapter 18-connects with your textbook

Google.classroom link or paper based

PhET Simulation for Acids and Bases

Explain at least 10 observations that you can make about acids and bases from this simulation. https://phet.colorado.edu/en/simulation/acid-base-solutions

Article Review Find a scientific article that discusses some of the topics we have covered this quarter and write a short paper (less than 1 page) that highlights a summary of the article and how the topic pertains to your life

https://phet.colorado.edu/en/simulation/acid-base-solutions

https://phet.colorado.edu/en/simulation/acid-base-solutions

Chem Unit 12.1 Notes Types of Mixtures

12.1 Types of Mixtures

What's in this stuff?

MixturesMixture: combination of two or more substances.

Heterogeneous mixtures: don’t blend smoothly – individual components remain distinct.

Homogeneous mixture: have uniform composition.

Heterogeneous MixturesSuspension: A mixture that contains particles that settle out if left undisturbed.

Example: Tanana River water.

Heterogeneous MixturesThixotropic Mixture: A solidlike mixture that separates into a liquid and solid layer when agitated.

Ex: Tanana River mud. Jiggling makes it separate through liquefaction.

Heterogeneous MixturesColloid: Mixture of dispersing medium and particles between 1 nm and 1000 nm. Particles don’t settle out.

1. Ex: Milk. medium = water particles = fat globules.

2. Ex: Jello. medium = gelatin networkparticles = water solution.

Heterogeneous MixturesBrownian Motion: movement of particles in a colloid. Particles collide with dispersion medium, never settling out.Tyndall Effect: Scattering of light passing through colloid particles. (Laser Demo)

http://en.wikipedia.org/wiki/File:Milk.jpg

Chem Unit 12.1 Notes Types of Mixtures

Homogeneous MixturesSolutions: substances composed of two or more components having uniform composition.

Solvent: Substance that dissolves something.

Solute: Substance that is dissolved. 3. Ex: Sugar in water solution – sugar is dissolved (solute), water dissolves it (solvent)

Homogeneous Solution TypesUnsaturated – More solute can be dissolved

Saturated – Solvent holds the maximum amount of solute. Rate of solvation equals rate of crystallization.

Supersaturated – An unstable situation – more solute is dissolved than ‘should’ be possible.

Happens when solute is dissolved at high temperature, and then the temp is reduced. (Sodium Acetate Demo)

Factors Speeding DissolutionAgitation – stirring

or shaking

Larger surface area – pulverize solute

Heating – solids dissolve faster in warm solvent

Gases do not dissolve in warm solvent, however, but do in cold solvent.

Other TermsSoluble: Solid that dissolves in a particular solvent.

Insoluble: Solid that doesn’t dissolve .

4. List three solid substances that don't dissolve in water.

Sand, steel, wood, granite.

Other Other TermsMiscible: When describing liquids – two liquids that will dissolve into each other.5. List two miscible liquids.

Glycol in water.

Immiscible: When two liquids won’t mix.6. List two immiscible liquids.Oil in water.

Homework

12.1 Problems. Due: Next Class.

Chem Unit 12.2 Notes Solutions & Concentration

12.2 Solution Concentration Lab SolutionsConcentration: amount of solute dissolved in solvent.

Care for a spot of tea?

Mass solute: 12.6 gMass solution: 12.6 g NaCl + 100.0 g water = 112.6 g

Percent by MassRatio of solute’s mass expressed as percent.

1. Ex: What is the % mass of a solution made of 12.6 grams NaCl and 100.0 grams water?

Percent by VolumeUsed when both solute and solvent are liquids: ratio of solute’s volume expressed as a percent (alcohol demo).

2. What is the % volume of ethanol in a solution containing 35 mL ethanol and 155 mL water?Volume solute: 35 mLVolume total: 35 mL + 155 mL = 190 mL

Molarity (M)Moles of solute dissolved per liter of solution:

Molarity units are mol/L.

Ex 3: what's the molarity if 1.8 moles NaCl are dissolved in water, making 2.5 liters of solution?

4. Another Molarity ExampleOften, you make a mass to mole conversion first.What is the molarity of a NaCl solution if 18 g are dissolved and made into a 0.25 L solution? NaCl molar mass = 58.44 g/mole.Moles of NaCl:

Then:

http://en.wikipedia.org/wiki/File:Volumetric_flasks.jpg

Chem Unit 12.2 Notes Solutions & Concentration

5. More Molarity!How many g NaCl are needed to make 1.8 L of a 0.35 M solution?First, calculate moles NaCl:

Last: moles to mass conversion (NaCl = 58.44 g/mol)

6. If you added NaCl to 1000 mL water, how would that affect concentration?You’d have a volume larger than 1 L: the solution would be less than 1 M.

Making SolutionsTo make 1.0 L of a 1.0 M aqueous solution of NaCl:1. Mass out one mole of NaCl (58.44 g).2. Dissolve in 500 mL of water in a Volumetric Flask.3. Add water to the 1000 mL mark.

Volumetric Flask

Diluting Molar Solutions

Dilution equation (from condition 1 to condition 2):

M = molarityV = volume

Stock solution: a concentrated solution.Dilute solution: a solution prepared from a stock solution.

7. Dilution ExampleTo what volume would you dilute 55 mL of a 3.5 M stock solution to get a concentration of 0.36 M?

8. Another Dilution ExampleWhat would the resulting concentration be, if 250 mL of 3.8 M NaCl were diluted to 1.0 L?First, realize V2 = 1000 mL

Homework

12.2 ProblemsDue: Next Class

Chem Unit 12.3 Notes Intro to Acids & Bases

Review!1. What element do all acids contain?

2. What polyatomic ion do bases contain?

3. What are the two products of an acid base reaction?

Hydrogen Ion: H+

Hydroxide Ion: OH

Water and an ionic compound (called a salt)

12.3 Introduction to Acids and Bases Physical:

Acids taste tart or sour: lemons, vinegarAcids turn blue litmus* paper red (Demo)Bases taste bitter and feel slippery: ever eaten soap?Bases turn red litmus* paper blue (Demo)* Litmus is a pH sensitive compound historically extracted from lichens. First used in the 1300's, the chromophore (color sensitive compound) in litmus is 7hydroxyphenoxozone.

Don’t identify chemicals by taste or feel!See Acid/Base Resource: P. 8.

Properties of Acids and Bases

Both acids and bases are electrolytes.

Acids can react with metals to produce hydrogen gas and a metal salt.

Demo: Zn + HCl à ZnCl2 + H2

Acids react with carbonates to produce carbon dioxide, water, and a salt (ionic compound). Demo: Limestone (CaCO3) + HCl.

Properties of Acids and Bases Hydronium and Hydroxide IonsWater hydrolyzes (breaks up) into hydroxide and hydrogen ions. The hydrogen ions merge with water forming hydronium ions (H3O+).

In a neutral solution (pH = 7), these ions are equal.In acids, (pH < 7) hydronium outnumbers hydroxide. In bases (pH > 7) hydroxide outnumbers hydronium.

Arrhenius model of acids/basesSvante Arrhenius in 1883 proposed a model that defined acids as substances that contain hydrogen atoms which ionize in water.

Bases contain hydroxide ions.

H+ OH H+ OH

H+ OH

HCl

NaOHKOH

H2SO4

Zn(OH)2

4. You do!Move the following chemicals into the acid or base corrals!

Acids

Bases

Chem Unit 12.3 Notes Intro to Acids & Bases

HCl + H2O H3O+ + Cl

BrønstedLowry ModelFocuses on H+ transfer: an acid is a H+ donor; a base is a H+ acceptor.

Example: HCl and water:

Here, water is a base because it accepts the H+ ion. Can give

up hydrogen.Can acceptHydrogen

HCl + H2O H3O+ + Cl

ConjugatesIn accepting H+, a base becomes a Conjugate Acid. In giving up a H+, an acid becomes a Conjugate Base.

5. Example:

From our example, on the product side, the hydronium can give up H+, and the chloride can accept one.

6. Ammonia ExampleAmmonia (NH3) acts as a base in aqueous solution, because it absorbs a hydrogen from water, becoming the ammonium ion.

Which is the conjugate acid, and which is the conjugate base of this reaction?

NH3 + H2O NH4+ + OH

The different components can be paired up:Acid – conjugate base pair: water hydroxide ion.Base – conjugate acid pair: ammonia ammonium ion.

AcidBaseConjugate

AcidConjugate

BaseNH3 + H2O NH4

+ + OH

6. Ammonia Example

Mono and Polyprotic acidsMonoprotic acids have one ionizable hydrogen ion. Polyprotic – “many protons”, such as:Diprotic = two. Ex: sulfuric acid.Triprotic = three. Ex: phosphoric acid.

7. Why is acetic acid (vinegar)(CH3COOH) monoprotic? The H atoms connected to carbon don't dissociate.

Sulfuric Acid has two ionizable hydrogen atoms.

Homework12.3 Problems.Due: Next Class.

Chem Unit 12.4 Notes Strengths of Acids & pH

1. What makes an acid or base strong?It’s got nothing to do with whether it eats holes in things, or its concentration.Strong acids or bases ionize completely in water and are good electrolytes; weak ones do/are not. Demo Class models acetic acid (5% ionized).

(Resources 8)12.4 Strengths of Acids and Bases Acid Demo

Concentrated, strong acids are dangerous! Paper Sugar

Ion Product of WaterWater selfreacts to form a hydroxide ion (OH) and a hydronium ion (H3O+):

The concentration of these ions in pure water is low:1.0 E 7 M.

pHAn expression of acidity:Low pH = acidic, high pH = basic.

Mathematically:

[H+] = hydrogen ion concentration (M).

LOG

Calculator Tutorial:Press the button.Press the button.Enter hydrogen ion concentration.

()

2. pH Example AWhat is the pH of a 0.03 M solution of HCl?

Find the concentration of hydrogen ions first. HCl breaks up in a 1:1 ratio, so a 0.03 M solution of HCl yields a 0.03 M concentration of H+ and Cl ions.

3. pH Example BWhat is the pH of a 0.008 M solution of H2SO4?

Find the concentration of hydrogen ions first.

H2SO4 breaks up in a 2 H+:1 SO42 ratio:

0.008 M H2SO4 yields a 0.016 M concentration of H+ ions.

Chem Unit 12.4 Notes Strengths of Acids & pH

pOHLike pH, but looks at hydroxide ion concentration.

Mathematically:

[OH] = hydroxide ion concentration (M).

For any aqueous solution:pH + pOH = 14.00.

4. pOH ExampleWhat is the pOH of the solution in Example 2? The pH was 1.79.

()

From pH or pOH, molar concentration is:

Calculator Tutorial: Press , then the button (10x function).Press the button.Enter pH (or pOH).

Or:

LOG2nd

Concentration 5. Molarity from pH ExampleWhat is HNO3 molarity if pH = 2.5 ?

OHH+

Salt Hydrolysis.Salts form acidic, basic or neutral solutions in water.Weak acids and strong bases make basic salts, Strong acids and weak bases make acidic salts.Neutral salts: equally strong (or weak) acids and bases.As they dissolve, they hydrolyze water (break it apart), releasing or combining with H+ or OH ions.Ex: Sodium fluoride (NaF) is a basic salt because it's made from NaOH (strong base) and HF (weak acid).

Na+F

6. Parent Chemical Example

What are the parent chemicals of ZnSO4?Will it be acidic, basic or neutral in water?

Zn(OH)2 (weak base), and H2SO4 – (strong acid).It forms an acidic solution.


Chem Unit 12.5 Notes Neutralization

12.5 NeutralizationWarning! Neutralization Lab Next Class!

1. Lab Quiz

What do you neutralize an acid spill with?Baking soda!

Acid Base ReactionsIn a neutralization reaction, an acid and a base will react and produce an ionic compound and water.

Ionic compound (called a 'salt') made of a cation from the base and an anion from the acid.In the process, the pH of the reaction mixture will approach 7.0 (neutral). Mg(OH)2 + 2 HCl à MgCl2 + 2 H2O

2. Neutralization ExampleBalance the neutralization reaction of magnesium hydroxide and hydrochloric acid.

Correct chemical formulas are essential:magnesium hydroxide = Mg(OH)2hydrochloric acid.= HCl

TitrationTitration: Method of determining concentration.

React a known volume of an unknown concentration with an amount of a known solution (called a titrant).Ex: to determine the concentration of an unknown acid, use a measured amount of a base of known concentration.

Procedure1. Put a measured volume of unknown concentration of acid or base in a beaker.

2. Fill A buret with a titrant of known concentration.

3. Add measured volumes of titrant (called aliquots) until the reaction reaches the equivalence point (end point).

A Buret

Chem Unit 12.5 Notes Neutralization

Equivalence Point (End Point)Def: The point in a neutralization when moles of H+ and OH equal each other.How is this point determined?1. pH meter (if available): stop reaction at desired pH.2. Indicators change color at a specific pH: Phenolpthalien: clear to pink above pH = 8.2, Bromothymol Blue: yellow to blue above pH = 6.8.

(Demo with indicators in test tubes)

Not useful if necessary pH level is different than indicator's changing pH, or if solution is colored.

1. Write a balanced acidbase reaction.2. Determine hydrogen ions of acid, and hydroxide ions of base. 3. Use the equation:

# H+ = acid's hydrogen numberMA = Acid’s molarityVA = Acid’s volume # OH = base's hydroxide numberMB = Base’s molarityVB = Base’s volume

Calculating Concentration

NaOH + HCl NaCl + H2O

3. Titrating NaOH with HClObserve this procedure so the lab makes sense!

Reaction:Calculate NaOH:

Data Chart

NaOH Volume 25.0 mLHCl Concentration 0.25 M

Beginning HCl Volume 0.0 mLEnding HCl Volume 16.6 mLTotal HCl Volume 16.6 ml

16.625.0

0.166 M


Unit 12 Test Preparation Questions

Name _____________________________________________ Date ____________________ Class ___________________

Chemistry: Matter and Change Study Guide

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14

Mixtures and Solutions

Section 14.1 Heterogeneous and Homogeneous Mixtures In your textbook, read about suspensions and colloids.

For each statement below, write true or false.

____________ 1. A solution is a mixture containing particles that settle out of the mixture if left undisturbed.

____________ 2. The most abundant substance in a colloid is the dispersion medium.

____________ 3. A colloid can be separated by filtration.

____________ 4. A solid emulsion consists of a liquid dispersed in a solid.

____________ 5. Whipped cream is an example of a foam.

____________ 6. In an aerosol, the dispersing medium is a liquid.

____________ 7. Brownian motion results from the collisions of particles of the dispersion medium with the dispersed particles.

____________ 8. Dispersed particles in a colloid do not tend to settle out because they have polar or charged atomic groups on their surfaces.

____________ 9. Stirring an electrolyte into a colloid stabilizes the colloid.

____________ 10. Colloids demonstrate the Tyndall effect.

The table below lists the characteristics of particles in colloids, solutions, and suspensions. Place a check in the column of each mixture whose particles have a particular characteristic.

Characteristics of Particles Colloid Solution Suspension

11. Less than 1 nm in diameter

12. Between 1 nm and 1000 nm in diameter

13. More than 1000 nm in diameter

14. Settle out if undisturbed

15. Pass through standard filter paper

16. Lower vapor pressure

17. Scatter light

Name _____________________________________________ Date ____________________ Class ___________________


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13 14

14 Section 14.2 Solution Concentration In your textbook, read about expressing concentration and using percent to describe concentration.

Data related to aqueous solutions of sodium chloride (NaCl) and aqueous solutions of ethanol (C2H5OH) are provided in the table below. Use the table to answer the following questions. Circle the letter of the choice that best answers the question.

Mass (g) Volume (mL)

Solution NaCl H2O Solution C2H5OH H2O 1 3.0 100.0 5 2.0 100.0

2 3.0 200.0 6 5.0 100.0

3 3.0 300.0 7 9.0 100.0

4 3.0 400.0 8 15.0 100.0

1. What is the percent by mass of NaCl in solution 1? a. 0.030% b. 2.9% c. 3.0% d. 33%

2. Which of the following solutions is the most dilute? a. Solution 1 b. Solution 2 c. Solution 3 d. Solution 4

3. What is the percent by volume of C2H5OH in Solution 5? a. 0.2% b. 1.9% c. 2.0% d. 22%

4. Which of the following solutions is the most concentrated? a. Solution 5 b. Solution 6 c. Solution 7 d. Solution 8

In your textbook, read about molarity and preparing molar solutions.

Read the following problem and then answer the questions.

An 85.0-mL aqueous solution contains 7.54 g iron(II) chloride (FeCl2). Calculate the molarity of the solution.

5. What is the mass of the solute? ___________________________________________________________________

6. What is the volume of the solution? _______________________________________________________________

7. Write the equation that is used to calculate molarity.

______________________________________________________________________________________________

8. In what unit must the amount of the solute be expressed to calculate molarity? ______________________________

9. In what unit must the volume of the solution be expressed to calculate molarity? ____________________________

10. Write the expression needed to convert the volume of the solution given in the problem to the volume needed to calculate molarity. __________________________________________________________

Name _____________________________________________ Date ____________________ Class ___________________


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13 14

14 Section 14.2 continued

11. What quantity must be used to convert the mass of the solute given in the problem to the amount of solute needed to calculate molarity? ______________________________________________________________________________________________

12. Write the expression used to calculate the amount of solute. ______________________________________________________________________________________________

13. Calculate the molarity of the solution. Show all your work.

In your textbook, read about molality and mole fractions.

Answer the following questions.

14. How does molality differ from molarity? ______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

15. Calculate the molality of a solution of 15.4 g sodium bromide (NaBr) dissolved in 125 g of water. Show all your work.

16. What is mole fraction? ______________________________________________________________________________________________

______________________________________________________________________________________________

17. Calculate the mole fraction of HCl in an aqueous solution that contains 33.6% HCl by mass. Show all your work.

Name _____________________________________________ Date ____________________ Class ___________________


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14 Section 14.3 Solvation and Solubility? In your textbook, read about the characteristics of solutions.

Use each of the terms below just once to complete the passage.

immiscible liquid soluble solution

insoluble miscible solute solvent

Air is a(n) (1) ____________________ of oxygen gas dissolved in nitrogen gas.

The oxygen in air is the (2) ____________________, and nitrogen is the (3) ___________________.

Because oxygen gas dissolves in a solvent, oxygen gas is a(n) (4) __________________ substance.

A substance that does not dissolve is (5) ___________________. (6) _____________________ solutions

are the most common type of solutions. If one liquid is soluble in another liquid, such as acetic acid in

water, the two liquids are (7) _____________________. However, if one liquid is insoluble in another,

the liquids are (8) _____________________.

Read about solvation in aqueous solutions in your textbook.

The diagram shows the hydration of solid sodium chloride to form an aqueous solution. Use the diagram to answer the following questions.

9. Hydration is solvation in which the solvent is water. What is solvation? ______________________________________________________________________________________________

______________________________________________________________________________________________

Name _____________________________________________ Date ____________________ Class ___________________


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13 14

14 Section 14.3 continued

10. As sodium chloride dissolves in water, what happens to the sodium and chloride ions? ______________________________________________________________________________________________

______________________________________________________________________________________________

11. Explain the orientation of the water molecules around the sodium ions and chloride ions. ______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

12. How does the strength of the attraction between water molecules and sodium and chloride ions compare with the strength of the attraction between the sodium ions and chloride ions? How do you know? ______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

______________________________________________________________________________________________

13. List three ways that the rate of solvation may be increased. ______________________________________________________________________________________________

______________________________________________________________________________________________

In your textbook, read about heat of solution, solubility, and factors that affect solubility.


________ 14. The overall energy change that occurs when a solution forms is called the heat of solution.

________ 15. Solubility is a measure of the minimum amount of solute that dissolves in a given amount of solvent at a specified temperature and pressure.

________ 16. Solvation continues as long as the solvation rate is less than the crystallization rate.

________ 17. In a saturated solution, solvation and crystallization are in equilibrium.

________ 18. Additional solute can be dissolved in an unsaturated solution.

________ 19. The solubility of a gas dissolved in a liquid decreases as the temperature of the solution increases.

Name _____________________________________________ Date ____________________ Class ___________________


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14

Section 14.4 Colligative Properties of Solutions In your textbook, read about electrolytes and colligative properties, vapor pressure lowering, boiling point elevation, and freezing point depression.

Use the table to answer the following questions.

Solution Density (g/L) Boiling Point (°C)

Freezing Point (°C)

1.0m C2H5OH(aq) 1.05 100.5 -1.8

1.0m HCl(aq) 1.03 101.0 -3.7

1.0m NaCl(aq) 1.06 101.0 -3.7

2.0m NaCl(aq) 1.12 102.1 -7.4

1. Which properties in the table are colligative properties? ______________________________________________________________________________________________

2. What can you conclude about the relationship between colligative properties and the number of ions in solution from the 1.0m NaCl(aq) and 2.0m NaCl(aq) solutions? ______________________________________________________________________________________________

3. What can you conclude about the relationship between colligative properties and the type of ions in solution from the 1.0m HCl(aq) and 1.0m NaCl(aq) solutions? ______________________________________________________________________________________________

Suppose that in a simple system, a semipermeable membrane is used to separate a sucrose-water solution from its pure solvent, water. Match the descriptions of the system in Column A with the terms in Column B.

Column A Column B

________ 4. Cannot cross the semipermeable membrane

________ 5. Can cross the semipermeable membrane

________ 6. The side that exerts osmotic pressure

________ 7. The diffusion of the solvent particles across the semipermeable membrane from the area of higher solvent concentration to the area of lower solvent concentration

________ 8. The barrier with tiny pores that allow some particles to pass through but not others

________ 9. The side from which more water molecules cross the semipermeable membrane

________ 10. A colligative property of solutions

a. osmotic pressure

b. water molecules

c. semipermeable membrane

d. sugar molecules

e. osmosis

f. solution side

g. pure solvent side

Name _____________________________________________ Date ____________________ Class ___________________


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Acids and Bases

Section 18.1 Acids and Bases: An Introduction In your textbook, read about the properties of acids and bases.

For each description below, write acid if it tells about a property of an acid or base if it tells about a property of a base. If the property does not apply to either an acid or a base, write neither. If it applies to both an acid and a base, write both.

____________________ 1. Can turn litmus paper a different color

____________________ 2. Reacts with certain metals

____________________ 3. Contains more hydrogen ions than hydroxide ions

____________________ 4. Feels slippery

____________________ 5. Reacts with carbonates

____________________ 6. Feels rough

____________________ 7. Contains equal numbers of hydrogen and hydroxide ions

____________________ 8. Tastes bitter

____________________ 9. Tastes sour

In your textbook, read about the different models of acids and bases.

Use the terms below to complete the passage. You may use each term more than once.

Arrhenius Brønsted-Lowry conjugate acid

conjugate base hydrogen hydroxide

The (10) ________________ model of acids and bases states that an acid contains the element

(11) ___________________ and forms ions of this element when it is dissolved in water. A base contains

the (12) _____________________ group and dissociates to produce (13) __________________________

ions in aqueous solution.

According to the (14) ___________________ model, an acid donates (15) __________________ ions,

and a base accepts (16) ______________________ ions. According to this model, in an acid-base reaction,

each acid has a (17) ______________________, and each base has a (18) _______________________.

Name _____________________________________________ Date ____________________ Class ___________________


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13 18

Section 18.2 Strengths of Acids and Bases In your textbook, read about strengths of acids.

Circle the letter of the choice that best completes the statement or answers the question.

1. Acid A and acid B are of equal concentration and are tested with a conductivity apparatus. When the electrodes are placed in acid A, the bulb glows dimly. When they are placed in acid B, the bulb glows more brightly. Which of the following is true? a. Acid A is stronger than acid B. b. Acid B is stronger than acid A. c. Acid A and acid B are of equal strength. d. No comparison of strength can be made from the results.

2. A chemical equation for the ionization of an acid uses a single arrow to the right (®) to separate the reactant and product sides of the equation. Which of the following is true? a. The arrow does not indicate relative strength. c. The ionizing acid is strong. b. The ionizing acid is half ionized. d. The ionizing acid is weak.

3. Sulfuric acid is a strong acid. What is true about its conjugate base? a. Its conjugate base is amphoteric. b. Its conjugate base is strong. c. Its conjugate base is weak. d. No conclusion can be made regarding the strength of the conjugate base.

4. In solution, a weak acid produces a. a mixture of molecules and ions. c. all molecules. b. all ions. d. anions, but no hydronium ions.

5. Why are Ka values all small numbers? a. The concentration of water does not affect the ionization. b. The equilibrium is not stable. c. The solutions contain a high concentration of ions. d. The solutions contain a high concentration of un-ionized acid molecules.

6. Which of the following dissociates entirely into metal ions and hydroxide ions in solution? a. a strong acid b. a strong base c. a weak acid d. a weak base

7. In general, compounds formed from active metals, and hydroxide ions are a. strong acids. b. strong bases. c. weak acids. d. weak bases.

Name _____________________________________________ Date ____________________ Class ___________________


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13 18

Section 18.3 Hydrogen Ions and pH In your textbook, read about the ion product constant for water.

Answer the following questions.

1. Write the simplest form of the chemical equation for the self-ionization of water. ______________________________________________________________________________________________

2. Write the equilibrium constant expression, Keq, for this equation. ______________________________________________________________________________________________

3. Write the expression for the equilibrium constant for water, Kw. ______________________________________________________________________________________________

4. Why can the concentration of water be ignored in the equilibrium expression for water? ______________________________________________________________________________________________

5. What is the numerical value of Kw at 298 K? ______________________________________________________________________________________________

6. In solution, if the hydroxide ion concentration increases, what happens to the hydrogen ion concentration? ______________________________________________________________________________________________

7. If the concentration of hydroxide ions in solution is 1.0´10 -6, what is the hydrogen ion concentration? ______________________________________________________________________________________________

8. Is the solution in question 7 acidic, basic, or neutral? Explain. ______________________________________________________________________________________________

In your textbook, read about pH and pOH.

In the space at the left, write true if the statement is true; if the statement is false, change the italicized word or number to make it true.

____________________ 9. The pH of a solution is the negative logarithm of its hydroxide ion concentration.

____________________ 10. Values for pH range from 0 to 14.

____________________ 11. Stomach contents can have a pH of 2, which means that they are basic.

____________________ 12. The hydrogen ion concentration in a solution with a pH of 3 is two times greater than the hydrogen ion concentration in a solution with a pH of 5.

Name _____________________________________________ Date ____________________ Class ___________________


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13 18

___________________ 13. The pH of a neutral solution at room temperature equals the pOH of the solution.

___________________ 14. If the pH of a solution is 3, its pOH is 10.

___________________ 15. The pH of a solution with a [H+] of 1´10-8 is 8.

___________________ 16. The pH of a solution with a [OH-] of 1´10-6 is 6.

In your textbook, read about calculating the pH of acids and bases.

Solve each of the following problems. Show your work.

17. What is the pH of a 4.3´10-2M HCl solution? HCl is a strong acid.

18. Calculate the pH of a 5.2´10-3M H2SO4 solution? H2SO4 is a strong acid.

19. What is the pH of a 2.5´10-5M NaOH solution? NaOH is a strong base.

20. Calculate the pH of a 3.6´10-6M Ca(OH)2 solution. Ca(OH)2 is a strong base.

In your textbook, read about measuring pH.

Complete the passage.

Indicator paper can be used to measure the (21) ______________ of a solution. Indicators are

substances that are different (22) ________________ depending on the pH of the solution tested. Another

way to measure the acidity of the solution is the (23) ______________, which uses electrodes placed in

solution to directly read the results.

Name _____________________________________________ Date ____________________ Class ___________________


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18

Section 18.4 Neutralization In your textbook, read about neutralization and titration.

For each item in Column A, write the letter of the matching item in Column B.

Column A Column B

_______ 1. A chemical dye that changes color based on the pH of a solution

_______ 2. A method for using a neutralization reaction to determine he concentration of a solution

_______ 3. A reaction in which an acid and a base react to produce a alt and water

_______ 4. A solution of known concentration

_______ 5. An ionic product of an acid-base reaction

_______ 6. The point in a titration in which an indicator changes color

_______ 7. The stoichiometric point of a titration

a. acid-base indicator

b. end point

c. equivalence point

d. neutralization

e. salt

f. standard solution

g. titration

Complete the following table, indicating the formula and name of the salt formed by a neutralization reaction between the listed acid and base.

Acid Base Salt formula Salt name 8. HCl KOH KCl potassium chloride 9. H2SO4 Mg(OH)2

10. H3PO4 NaOH

11. HNO3 Fe(OH)3

12. H3PO4 Ca(OH)2

In the space at the left, write 1 through 4 to show the correct sequence of the steps in performing a titration using a pH meter. Then, write 5 through 8 to sequence the steps used to calculate the concentration of the unknown solution.

Sequence of Steps

________ 13. Continue adding the standard solution to the solution of unknown concentration until the equivalence point is reached.

________ 14. Fill a buret with the standard solution.

________ 15. Start adding the standard solution slowly, with mixing, to the solution of unknown concentration, reading the pH at regular intervals.

Name _____________________________________________ Date ____________________ Class ___________________


49

13 18 Section 18.4 continued

________ 16. Use a pH meter to check the pH of a solution of known volume but unknown concentration.

Calculation _________ 17. Calculate the number of moles of acid or base in the volume of standard solution added.

_________ 18. Use the mole ratio from the balanced equation to calculate the number of moles of reactant in the unknown solution.

_________ 19. Use the number of moles and volume of the unknown solution to calculate molarity.

_________ 20. Write the balanced chemical equation for the neutralization reaction.

In your textbook, read about salt hydrolysis.

Complete the following concept map, using the terms acidic, basic, and neutral.

In your textbook, read about buffer solutions.


___________________ 24. Buffers resist change in pH.

___________________ 25. A buffer can be a mixture of a weak acid and its conjugate base.

___________________ 26. An example of a buffer solution is a mixture of acetic acid and sodiumacetate.

___________________ 27. A buffer solution changes pH only a small amount even if large amounts of acid or base are added.

___________________ 28. A buffer system should contain considerably more acid than base.

___________________ 29. Specific buffer systems should be chosen based on the pH that must be maintained.

unit 12-solutions & acids and bases

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