Chapter 8 Solutions, Acids, and Bases. 8.1 Formation of SolutionsSolutions, Acids, and Bases 8.1 Formation of Solutions Any state of matter – solid,

8.1 Formation of Sol8.1 Formation of Solutionsutions

Solutions, Acids, and BasesSolutions, Acids, and Bases

Chapter 8Chapter 8

Solutions, Acids, and Solutions, Acids, and BasesBases

8.1 Formation of Solutions8.1 Formation of Solutions Solutions, Acids, and BasesSolutions, Acids, and Bases

8.1 Formation of Solutions8.1 Formation of Solutions

Any state of matter – solid, liquid, or gas Any state of matter – solid, liquid, or gas – can become part of a solution. – can become part of a solution.

For a solution substance must dissolve in For a solution substance must dissolve in another.another.


DissolvingDissolving

A solution is a homogenous mixture of two A solution is a homogenous mixture of two or more substances. or more substances.

Every solution has two types of Every solution has two types of components. components. A solute is a substance whose particles A solute is a substance whose particles

are dissolved in a solutionare dissolved in a solution The substance in which the solute is The substance in which the solute is

dissolved is called the solvent. dissolved is called the solvent.


The solution takes the state of the The solution takes the state of the solvent. solvent.

Figure 2 lists some common solutions Figure 2 lists some common solutions and the states of their solutes and and the states of their solutes and solvents. solvents. For example nitrogen, 78% of air, is For example nitrogen, 78% of air, is

the solvent. the solvent. Oxygen, carbon dioxide, argon, and Oxygen, carbon dioxide, argon, and

other gases are the solutes. other gases are the solutes.


Substances can dissolve in water in three Substances can dissolve in water in three ways – dissociation, dispersion, and ways – dissociation, dispersion, and ionization. ionization.


Dissociation of Ionic Dissociation of Ionic CompoundsCompounds

For a solute to dissolve in water, the For a solute to dissolve in water, the solute and solvent particles must attract solute and solvent particles must attract one another. one another.

The particles within the solute are The particles within the solute are attracted to one another. attracted to one another.

The particles within the solvent are The particles within the solvent are attracted to one another. attracted to one another.


Before a solution can form, the attractions Before a solution can form, the attractions that hold the solute together and the that hold the solute together and the solvent together must be overcome.solvent together must be overcome.

Figure 3 illustrates how NaCl crystals Figure 3 illustrates how NaCl crystals dissolve in water. dissolve in water.

NaCl is an ionic compound. NaCl is an ionic compound. Water is a polar molecule and is attracted Water is a polar molecule and is attracted

to the ions in solute. to the ions in solute.


The crystal dissolves as the NaThe crystal dissolves as the Na++ and Cl and Cl−− ions are pulled into solution by the ions are pulled into solution by the surrounding water molecules. surrounding water molecules.

The process in which an ionic compound The process in which an ionic compound separates into ions as it dissolves is separates into ions as it dissolves is called dissociation.called dissociation.




Dispersion of Molecular Dispersion of Molecular CompoundsCompounds

Sugar dissolves in water by dispersion, Sugar dissolves in water by dispersion, or breaking into small pieces that spread or breaking into small pieces that spread throughout the water. throughout the water.

Both sugar and water are polar Both sugar and water are polar molecules, so they attract one another. molecules, so they attract one another.

Because the water molecules are Because the water molecules are constantly moving, they collide frequently constantly moving, they collide frequently with the sugar crystals. with the sugar crystals.


When enough water molecules have When enough water molecules have surrounded a sugar molecule, the surrounded a sugar molecule, the attractions between them are enough to attractions between them are enough to overcome the attractions holding the overcome the attractions holding the sugar molecule to the crystal. sugar molecule to the crystal.

The sugar molecule breaks free, and is The sugar molecule breaks free, and is pulled into solution. pulled into solution.


Ionization of Molecular Ionization of Molecular CompoundsCompounds

Hydrogen chloride is a molecular Hydrogen chloride is a molecular compound in which a hydrogen atom and compound in which a hydrogen atom and a chlorine atom share a pair of electrons. a chlorine atom share a pair of electrons.

When HCl gas dissolves in water, the HWhen HCl gas dissolves in water, the H++ from each HCl molecule is transferred to from each HCl molecule is transferred to a water molecule. a water molecule.

For each HCl molecule that reacts, a For each HCl molecule that reacts, a hydronium ion, Hhydronium ion, H33OO++, and a chloride ion, , and a chloride ion, ClCl−−, are produced. , are produced.


When hydrogen chloride and water form When hydrogen chloride and water form a solution, two molecular compounds a solution, two molecular compounds react to form two ions. react to form two ions.

The process in which neutral molecules The process in which neutral molecules gain or lose electrons is known as gain or lose electrons is known as ionization. ionization.


Unlike dissociation and dispersion, which Unlike dissociation and dispersion, which are physical changes, ionization is a are physical changes, ionization is a chemical change. chemical change.

When a solute dissolves by dissociation, When a solute dissolves by dissociation, the ions pulled into solution are the ions the ions pulled into solution are the ions present in the solute. present in the solute.

When a solute dissolves by ionization, When a solute dissolves by ionization, the ions in solution are formed by the the ions in solution are formed by the reaction of solute and solvent particles.reaction of solute and solvent particles.


Properties of Liquid SolutionsProperties of Liquid Solutions

Three physical properties of a solution Three physical properties of a solution that can differ from those of its solute and that can differ from those of its solute and solvent are solvent are conductivityconductivity freezing point freezing point boiling pointboiling point


ConductivityConductivity

The ions in solution will conduct an The ions in solution will conduct an electric current.electric current.


Freezing Point and Freezing Point and Boiling PointBoiling Point

Figure 6A shows how ice forms when Figure 6A shows how ice forms when water molecules are able to arrange water molecules are able to arrange themselves in a rigid structure. themselves in a rigid structure.

Figure 6B shows how the presence ions Figure 6B shows how the presence ions interferes with the freezing process. interferes with the freezing process.

Water at sea level freezes at 0Water at sea level freezes at 0ooC. C. Salt solutions can have a freezing point Salt solutions can have a freezing point

as low as −15as low as −15ooC. C.


A solute can also raise the boiling point A solute can also raise the boiling point of the solvent. of the solvent.

Ethylene glycol, CEthylene glycol, C22HH66OO22, raises the , raises the

boiling point and is used as a coolant in boiling point and is used as a coolant in car radiators to prevent overheating. car radiators to prevent overheating.


Heat of SolutionHeat of Solution

During formation of a solution, energy is During formation of a solution, energy is either released or absorbed. either released or absorbed.

Like chemical reactions, the solution Like chemical reactions, the solution process can be described as exothermic process can be described as exothermic or endothermic. or endothermic.

In order for a solution to form, both the In order for a solution to form, both the attractions among solute particles and attractions among solute particles and the attractions among solvent particles the attractions among solvent particles must be broken. must be broken.


Breaking attractions requires energy. Breaking attractions requires energy. As the solute dissolves, new attractions As the solute dissolves, new attractions

form between solute and solvent form between solute and solvent particles. particles.

The formation of attractions releases The formation of attractions releases energy. energy.

The difference between these energies is The difference between these energies is known as the heat of solution.known as the heat of solution.


Factors Affecting the Rates Factors Affecting the Rates of Dissolvingof Dissolving

Rates of dissolving depend on the Rates of dissolving depend on the frequency and energy of collisions that frequency and energy of collisions that occur between particles of the solute and occur between particles of the solute and solvent. solvent.

Factors that affect the rate of dissolving Factors that affect the rate of dissolving include: include: surface areasurface area stirringstirring temperature temperature



The greater the surface area of a solid The greater the surface area of a solid solute, the more frequent the collisions solute, the more frequent the collisions are between solute and solvent are between solute and solvent particles. particles.

More collisions result in a faster rate of More collisions result in a faster rate of dissolving. dissolving.

The more finely divided a solid solute is, The more finely divided a solid solute is, the faster it dissolves. the faster it dissolves.



Stirring moves dissolved particles away Stirring moves dissolved particles away from the surface of the solid and allows from the surface of the solid and allows for more collisions between solute and for more collisions between solute and solvent particles. solvent particles.

Substances dissolve faster when Substances dissolve faster when stirred.stirred.



Increasing the temperature of the solvent Increasing the temperature of the solvent will speed up the rate of reaction by will speed up the rate of reaction by causing the particles to move faster. causing the particles to move faster.

The solute goes into solution more The solute goes into solution more quickly because both the number of quickly because both the number of collisions and the energy of these collisions and the energy of these collisions increase.collisions increase.


8.2 Solubility and Concentration8.2 Solubility and Concentration Solutions, Acids, and BasesSolutions, Acids, and Bases

8.2 Solubility and 8.2 Solubility and ConcentrationConcentration


SolubilitySolubility

The maximum amount of a solute that The maximum amount of a solute that dissolves in a given amount of solvent at dissolves in a given amount of solvent at a constant temperature is called a constant temperature is called solubility. solubility.

Solubility is usually expressed in grams Solubility is usually expressed in grams of solute per 100 grams of solvent at a of solute per 100 grams of solvent at a specified temperature. specified temperature.


Depending on the amount of solute in Depending on the amount of solute in solution, solutions are described as solution, solutions are described as saturated, unsaturated, or saturated, unsaturated, or supersaturated. supersaturated.


Saturated SolutionsSaturated Solutions

Table sugar is very soluble in water. At Table sugar is very soluble in water. At 2020ooC, 203.9 g will dissolve in 100 g of C, 203.9 g will dissolve in 100 g of water.water.

If you try to dissolve more sugar in the If you try to dissolve more sugar in the same amount of water it will not dissolve. same amount of water it will not dissolve.

The solution is saturated. The solution is saturated. A saturated solution contains as much A saturated solution contains as much

solute as the solvent can hold at a given solute as the solvent can hold at a given temperature. temperature.


Unsaturated SolutionsUnsaturated Solutions

A solution that has less than the A solution that has less than the maximum amount of solute is called maximum amount of solute is called unsaturated. unsaturated.

A solution is unsaturated as long as the A solution is unsaturated as long as the amount of solute is less than the amount of solute is less than the solubility at that temperature. solubility at that temperature.


Supersaturated SolutionsSupersaturated Solutions

A solvent can sometimes dissolve more A solvent can sometimes dissolve more solute than expected, based on its solute than expected, based on its solubility. solubility.

If a solvent is heated above the specified If a solvent is heated above the specified temperature, more solute may dissolve. temperature, more solute may dissolve.


If the solvent is cooled back to the If the solvent is cooled back to the specified temperature, the extra solute specified temperature, the extra solute may stay in solution.may stay in solution.

A supersaturated solution contains more A supersaturated solution contains more solute than it can normally hold at a given solute than it can normally hold at a given temperature. temperature.

Supersaturated solutions are very Supersaturated solutions are very unstable.unstable.


Factors Affecting SolubilityFactors Affecting Solubility

Solubility varies not only with the solvent Solubility varies not only with the solvent used but also with the conditions of the used but also with the conditions of the solution process. solution process.

Factors that affect the solubility of a solute Factors that affect the solubility of a solute include:include: the polarity of the solvent the polarity of the solvent temperaturetemperature pressurepressure


Polar and Nonpolar Polar and Nonpolar SolventsSolvents

A common guideline for predicting A common guideline for predicting solubility is ‘like dissolves like.” solubility is ‘like dissolves like.”

Solution formation is more likely to Solution formation is more likely to happen when the solute and solvent are happen when the solute and solvent are either both polar or both nonpolar. either both polar or both nonpolar.


TemperatureTemperature

In general, the solubility of solids In general, the solubility of solids increases as the temperature of the increases as the temperature of the solvent increases. solvent increases.

Unlike most solids, gases usually Unlike most solids, gases usually become less soluble as the temperature become less soluble as the temperature of the solvent increases. of the solvent increases.


PressurePressure

To produce a carbonated beverage To produce a carbonated beverage manufacturers pressure to force COmanufacturers pressure to force CO22 to to

dissolve in the liquid. dissolve in the liquid. Increasing the pressure on a gas Increasing the pressure on a gas

increases its solubility in a liquid. increases its solubility in a liquid. The pressure of COThe pressure of CO22 in a sealed can of in a sealed can of

cola can be two or three times cola can be two or three times atmospheric pressure. atmospheric pressure.


Concentration of SolutionsConcentration of Solutions

The concentration of a solution is the The concentration of a solution is the amount of solute dissolved in a specified amount of solute dissolved in a specified amount of solution. amount of solution.

Concentration can be expressed as:Concentration can be expressed as: percent by volumepercent by volume percent by masspercent by mass molaritymolarity


Percent by VolumePercent by Volume

Percent by volume is determined by Percent by volume is determined by dividing the volume of solute by the dividing the volume of solute by the volume of solution. volume of solution.


Percent by MassPercent by Mass

Concentration expressed as a percent by Concentration expressed as a percent by mass is more useful when the solute is a mass is more useful when the solute is a solid. solid.

Percent by mass is the percent of a Percent by mass is the percent of a solution’s total mass that is accounted for solution’s total mass that is accounted for by the solute. by the solute.


MolarityMolarity

To compare the number of solute To compare the number of solute particles in solutions, chemists often use particles in solutions, chemists often use moles to measure concentration. moles to measure concentration.

A mole is the amount of a substance that A mole is the amount of a substance that contains 6.02 ×10contains 6.02 ×102323 particles of that particles of that substance. substance.

Molarity is the number of moles of a Molarity is the number of moles of a solute dissolved per liter of solution. solute dissolved per liter of solution.


Table sugar , CTable sugar , C1212HH2222OO1111, has a molar , has a molar

mass of 342 grams. mass of 342 grams. To make a 1-molar (1M) solution of table To make a 1-molar (1M) solution of table

sugar water, add 342 g of sugar to sugar water, add 342 g of sugar to enough water to make one liter of enough water to make one liter of solution. solution.

8.3 Properties of Acids and Bases8.3 Properties of Acids and Bases Solutions, Acids, and BasesSolutions, Acids, and Bases

8.3 Properties of Acids and 8.3 Properties of Acids and BasesBases


Identifying AcidsIdentifying Acids

An acid is a compound that produces An acid is a compound that produces hydronium (Hhydronium (H33OO++) ions when dissolved ) ions when dissolved

in water.in water. When hydrogen chloride gas dissolves When hydrogen chloride gas dissolves

in water, it ionizes and forms hydronium in water, it ionizes and forms hydronium ions and chlorine gas. ions and chlorine gas. HCl + HHCl + H22O → HO → H33OO++ + Cl + Cl−−


Some general properties of acids Some general properties of acids include:include: sour taste sour taste reactivity with metals reactivity with metals ability to produce color changes in ability to produce color changes in

indicators. indicators.


Sour TasteSour Taste

Foods that taste sour often contain acids. Foods that taste sour often contain acids. For example, lemons, limes, and oranges For example, lemons, limes, and oranges

contain citric acid., Ccontain citric acid., C66HH88OO7.7.

While many foods that are edible contain While many foods that are edible contain acids, NEVER test an acid by tasting it. acids, NEVER test an acid by tasting it.


Reactivity with MetalsReactivity with Metals

The reaction between an acid and a The reaction between an acid and a metal is an example of a single-metal is an example of a single-replacement reaction. replacement reaction. Zn + 2HCl → HZn + 2HCl → H22 + ZnCl + ZnCl22

shows how zinc replaces hydrogen in shows how zinc replaces hydrogen in hydrochloric acid, hydrogen gas and hydrochloric acid, hydrogen gas and zinc (II) chloride are produced. zinc (II) chloride are produced.


Color Changes in Color Changes in IndicatorsIndicators

An indicator is any substance that An indicator is any substance that changes color in the presence of an acid changes color in the presence of an acid or base. or base.

A common indicator is litmus, a dye A common indicator is litmus, a dye derived from lichens. derived from lichens.

Blue litmus paper turns red in the Blue litmus paper turns red in the presence of an acid. presence of an acid.


If an unknown solution is dropped on If an unknown solution is dropped on blue litmus paper and the paper turns blue litmus paper and the paper turns red, the solution can be classified as an red, the solution can be classified as an acid. acid.


Acetic acid CH3COOH Vinegar

Carbonic acid H2CO3 Carbonated beverages

Hydrochloric acid HCI Digestive juices in stomach

Nitric acid HNO3 Fertilizer production

Phosphoric acid H3PO4 Fertilizer production

Sulfuric acid H2SO4 Battery acid


Identifying BasesIdentifying Bases

A base is a compound that produces A base is a compound that produces hydroxide ions (OHhydroxide ions (OH−−) when dissolved in ) when dissolved in water. water.

When sodium hydroxide dissolves in When sodium hydroxide dissolves in water, it dissociates into sodium ions and water, it dissociates into sodium ions and hydroxide ions. hydroxide ions. NaOH → NaNaOH → Na++ + OH + OH−−


Some general properties of bases Some general properties of bases include:include: bitter tastebitter taste slippery feel slippery feel the ability to produce color changes in the ability to produce color changes in

indicators. indicators.


Unlike acids, bases usually do not react Unlike acids, bases usually do not react with metals. with metals.

Low reactivity with metals is not Low reactivity with metals is not considered a general property of bases. considered a general property of bases.


Bitter TasteBitter Taste

Unsweetened chocolate tastes bitter due Unsweetened chocolate tastes bitter due to the presence of a base called to the presence of a base called theobromine, Ctheobromine, C77HH88NN44OO22. .


Slippery FeelSlippery Feel

Bases feel slippery. Bases feel slippery. Wet soap and many cleaning products Wet soap and many cleaning products

that contain bases are slippery to the that contain bases are slippery to the touch. touch.

Some wet rocks feel slippery because Some wet rocks feel slippery because the water dissolves compounds in the the water dissolves compounds in the rocks and produces a basic solution. rocks and produces a basic solution.


Aluminum hydroxide Al(OH)3 Deodorant, antacid

Calcium hydroxide Ca(OH)2 Concrete, plaster

Magnesium hydroxide Mg(OH)2 Antacid, laxative

Sodium hydroxide NaOH Drain cleaner, soap production


Color Changes in Color Changes in IndicatorsIndicators

Bases turn red litmus paper blue. Bases turn red litmus paper blue. Phenolphthalein is another example of an Phenolphthalein is another example of an

acid-base indicator. acid-base indicator. In a solution containing a base, In a solution containing a base,

phenolphthalein is red. phenolphthalein is red. In a solution containing an acid, In a solution containing an acid,

phenolphthalein is colorless. phenolphthalein is colorless.


The plant, hydrangea, is a natural The plant, hydrangea, is a natural indicator. indicator.

When grown in acidic soil, hydrangeas When grown in acidic soil, hydrangeas have bluish-purple flowers. have bluish-purple flowers.

When they are grown in basic soil, the When they are grown in basic soil, the flowers are pink. flowers are pink.




Neutralization and SaltsNeutralization and Salts

The reaction between an acid and a base The reaction between an acid and a base is called neutralization. is called neutralization.

During neutralization, the negative ions in During neutralization, the negative ions in an acid compound combine with the an acid compound combine with the positive ions in a base to produce an positive ions in a base to produce an ionic compound called a salt. ionic compound called a salt.


At the same time, the hydronium ions At the same time, the hydronium ions from the acid combine with the hydroxide from the acid combine with the hydroxide ions from the base to produce water. ions from the base to produce water.

The neutralization reaction between an The neutralization reaction between an acid and a base produces a salt and acid and a base produces a salt and water. water.


Sodium chloride NaCl Food flavoring, preservative

Sodium carbonate Na2CO3 Used to make glass

Potassium chloride KCl Used as a salt substitute to reduce dietary intake of sodium

Potassium iodide Kl Added to table salt to prevent iodine deficiency

Magnesium chloride MgCl2 De-icer for roads

Calcium carbonate CaCO3 Chalk, marble floors, and tables

Ammonium nitrate NH4NO3 Fertilizer, cold packs


Proton Donors and AcceptorsProton Donors and Acceptors

Hydronium ions are produced when acids Hydronium ions are produced when acids dissolve in water. dissolve in water.

When an acid and a base react in water, When an acid and a base react in water, a proton from the hydronium ion from the a proton from the hydronium ion from the acid combines with the hydroxide ion acid combines with the hydroxide ion from the base to form water. from the base to form water.


Acids lose, or “donate” protons. Acids lose, or “donate” protons. Bases “accept” protons forming water. Bases “accept” protons forming water. Acids can be defined as proton donors Acids can be defined as proton donors

and bases can be defined as proton and bases can be defined as proton acceptors. acceptors.

This definition allows a wider range of This definition allows a wider range of substances to be classified as acids or substances to be classified as acids or bases. bases.


Based on earlier definitions water is Based on earlier definitions water is neither an acid nor a base. neither an acid nor a base.

Using the proton-donor or proton-Using the proton-donor or proton-acceptor definition, water can be either acceptor definition, water can be either an acid or a base depending on the an acid or a base depending on the compound with which it reacts.compound with which it reacts.

8.4 Strength of Acids and Bases8.4 Strength of Acids and Bases Solutions, Acids, and BasesSolutions, Acids, and Bases

8.4 Strength of Acids and 8.4 Strength of Acids and BasesBases

One way to describe the acidity or One way to describe the acidity or basicity is to determine the concentration basicity is to determine the concentration of hydronium or hydroxide ions present in of hydronium or hydroxide ions present in solution. solution.

Another way is to describe how readily Another way is to describe how readily those ions are formed. those ions are formed.


The pH ScaleThe pH Scale

Chemists use a number scale from 0 to Chemists use a number scale from 0 to 14 to describe the concentration of 14 to describe the concentration of hydronium ions in a solution. hydronium ions in a solution.

It is known as the pH scale. It is known as the pH scale. The pH of a solution is a measure of its The pH of a solution is a measure of its

hydronium ion concentration. hydronium ion concentration.


The pH ScaleThe pH Scale


A pH of 7 indicates a neutral solution. A pH of 7 indicates a neutral solution. Acids have a pH less than 7. Acids have a pH less than 7. Bases have a pH greater than 7. Bases have a pH greater than 7. Distilled water falls in the middle of the Distilled water falls in the middle of the

pH scale.pH scale.


Water ionizes slightly. Water ionizes slightly. 2H2H22O O H H33OO++ + OH + OH−−

The arrow to the left is longer than the The arrow to the left is longer than the arrow to the right showing that water arrow to the right showing that water contains more molecules than ions. contains more molecules than ions.


Water is neutral because is has equal Water is neutral because is has equal concentrations of hydronium and concentrations of hydronium and hydroxide ions. hydroxide ions.


If an acid is added to water, the If an acid is added to water, the concentration of Hconcentration of H33OO++ increases and the increases and the

concentration of OHconcentration of OH−− decreases. decreases. The lower the pH value, the greater the The lower the pH value, the greater the

HH33OO++ ion concentration in solution is. ion concentration in solution is.


If a base is added to water, the If a base is added to water, the concentration of OHconcentration of OH−− increases and the increases and the concentration of Hconcentration of H33OO++ decreases. decreases.

The higher the pH value, the lower the The higher the pH value, the lower the HH33OO++ ion concentration is. ion concentration is.


Strong Acids and BasesStrong Acids and Bases

Some reactions go to completion while Some reactions go to completion while others reach equilibrium. others reach equilibrium.

When certain acids and bases dissolve in When certain acids and bases dissolve in water, the formation of ions from the water, the formation of ions from the solute almost goes to completion. solute almost goes to completion.

Such acids and bases are classified as Such acids and bases are classified as strong. strong.


Strong AcidsStrong Acids

Hydrochloric acid is a strong acid.Hydrochloric acid is a strong acid. When hydrogen chloride dissolves in When hydrogen chloride dissolves in

water, almost all of its molecules ionize. water, almost all of its molecules ionize. When strong acids dissolve in water, they When strong acids dissolve in water, they

ionize almost completely. ionize almost completely. Other strong acids include: sulfuric acid Other strong acids include: sulfuric acid

(H(H22SOSO44), and nitric acid (HNO), and nitric acid (HNO33). ).


Strong BasesStrong Bases

Sodium hydroxide is an example of a Sodium hydroxide is an example of a strong base. strong base.

When dissolved in water, sodium When dissolved in water, sodium hydroxide almost completely dissociates hydroxide almost completely dissociates into sodium and hydroxide ions. into sodium and hydroxide ions.

Strong bases dissociate almost completely Strong bases dissociate almost completely in water. in water.


Other strong bases include calcium Other strong bases include calcium hydroxide {Ca(OH)hydroxide {Ca(OH)22}, and potassium }, and potassium

hydroxide (KOH). hydroxide (KOH).


Weak Acids and BasesWeak Acids and Bases

Weak acids and bases ionize or Weak acids and bases ionize or dissociate only slightly in water. dissociate only slightly in water.


Weak AcidsWeak Acids

A weak acid forms fewer hydronium ions A weak acid forms fewer hydronium ions than a strong acid of the same than a strong acid of the same concentration and has a higher pH than a concentration and has a higher pH than a strong acid. strong acid.

Concentration is the amount of solute Concentration is the amount of solute dissolved in a given amount of solution. dissolved in a given amount of solution.

Strength refers to the solute’s tendency Strength refers to the solute’s tendency to form ions in water. to form ions in water.


A strong acid may not have a low pH A strong acid may not have a low pH because concentration also affects pH because concentration also affects pH value. value.

For example, a dilute solution of HCl can For example, a dilute solution of HCl can have a pH of 6 and a concentrated have a pH of 6 and a concentrated solution of CHsolution of CH33COOH can have a pH of COOH can have a pH of

3. 3.


Weak BasesWeak Bases

When ammonia, NHWhen ammonia, NH33, dissolves in water , dissolves in water

very little ionizes. very little ionizes. It produces few hydroxide ions and It produces few hydroxide ions and

makes a weak base. makes a weak base.


BuffersBuffers

Weak acids and bases can be used to Weak acids and bases can be used to make buffers. make buffers.

A buffer is a solution that is resistant to A buffer is a solution that is resistant to large changes in pH. large changes in pH.

Buffers can be prepared by mixingBuffers can be prepared by mixing a weak acid and its salt a weak acid and its salt a weak base and its salt. a weak base and its salt.


ElectrolytesElectrolytes

An electrolyte is a substance that ionizes An electrolyte is a substance that ionizes or dissociates when it dissolves in water. or dissociates when it dissolves in water.

The electrolytes in sports drinks help The electrolytes in sports drinks help restore balance of ions in the body. restore balance of ions in the body.


Strong acids and bases are strong Strong acids and bases are strong electrolytes because they dissociate or electrolytes because they dissociate or ionize almost completely in water. ionize almost completely in water.

Salts also make strong electrolytes. Salts also make strong electrolytes.


Space shuttles use fuel cells to provide Space shuttles use fuel cells to provide electricity. electricity.

The fuel cells use the strong base The fuel cells use the strong base potassium hydroxide as an electrolyte. potassium hydroxide as an electrolyte.

The fuel cells use oxygen and hydrogen The fuel cells use oxygen and hydrogen instead of metal electrodes. instead of metal electrodes.

The fuel cells also produce water.The fuel cells also produce water.

Documents

Chapter 8 Solutions, Acids, and Bases. 8.1 Formation of SolutionsSolutions, Acids, and Bases 8.1 Formation of Solutions Any state of matter – solid,