NOTES 10 – Acids, Bases, & pH. Ion Review An ion is an atom that gains or loses electrons giving it an overall positive or negative charge An ion is an.

NOTES 10 – Acids, Bases, & pHNOTES 10 – Acids, Bases, & pH

Ion ReviewIon Review An ion is an atom that gains or loses electrons An ion is an atom that gains or loses electrons

giving it an overall positive or negative chargegiving it an overall positive or negative charge Lose electrons = positively charged ionLose electrons = positively charged ion Gain electrons = negatively charged ionGain electrons = negatively charged ion

Sometimes a compound acts like an ionSometimes a compound acts like an ion Hydrogen atoms have 1 proton and 1 electronHydrogen atoms have 1 proton and 1 electron Compounds that take hydrogen’s electron can Compounds that take hydrogen’s electron can

become negative ions (more electrons than become negative ions (more electrons than protons)protons)

The leftover hydrogen proton becomes a The leftover hydrogen proton becomes a positive hydrogen ionpositive hydrogen ion

Water Molecules Form IonsWater Molecules Form Ions

Water molecules break apart into ions and then Water molecules break apart into ions and then reform into moleculesreform into molecules

Water forms two different ionsWater forms two different ions Hydrogen IonsHydrogen Ions = = HH++

Hydroxide IonsHydroxide Ions = = OHOH--

HH22O O H H++ + OH + OH--

When water breaks into ions, it is called When water breaks into ions, it is called dissociationdissociation (Water (Water dissociatesdissociates into ions) into ions)

In pure water there are equal numbers of In pure water there are equal numbers of hydrogen and hydroxide ionshydrogen and hydroxide ions

Dissociation of WaterDissociation of Water

In any sample of water, very few of In any sample of water, very few of the molecules are dissociated at the molecules are dissociated at any one timeany one time

About 1 in 550 million  About 1 in 550 million  There is constant change There is constant change As one hydrogen ion reattaches to As one hydrogen ion reattaches to

a hydroxide ion to form a water a hydroxide ion to form a water molecule, another water molecule molecule, another water molecule dissociates to replace the hydrogen dissociates to replace the hydrogen ion and the hydroxide ion in ion and the hydroxide ion in solutionsolution

What are acids?What are acids? AcidAcid – a compound that increases the number – a compound that increases the number

of hydrogen ions (Hof hydrogen ions (H++) when dissolved in water) when dissolved in water In water, acids dissociate producing HIn water, acids dissociate producing H++ ions ions Acidic solutions (acid substance + water) have Acidic solutions (acid substance + water) have

more hydrogen ions than hydroxide ions (More more hydrogen ions than hydroxide ions (More HH++ than OH than OH--))

Acids taste sourAcids taste sour Acids can cause burnsAcids can cause burns Acids can be good conductors of electricityAcids can be good conductors of electricity EX. acetic acid, citric acid, ascorbic acid EX. acetic acid, citric acid, ascorbic acid

Strong Vs. Weak AcidsStrong Vs. Weak Acids Strong acids ionize completelyStrong acids ionize completely

Every molecule of the acid produces HEvery molecule of the acid produces H++ ions ions and negative acid ionsand negative acid ions

Strong acids have a pH in the range of 0 to 3Strong acids have a pH in the range of 0 to 3 EX. Nitric acid in waterEX. Nitric acid in water

HNOHNO33 H H++ + NO + NO33--

Weak acids do not ionize completelyWeak acids do not ionize completely Some molecules form ions, some do notSome molecules form ions, some do not Weak acids have a pH above 3Weak acids have a pH above 3 EX. Acetic acid in waterEX. Acetic acid in water

CHCH33COOH COOH CH CH33COOCOO-- + H + H++

Acids Are Useful But Can Be DangerousAcids Are Useful But Can Be Dangerous

Acids are used for cleaning, in batteries, Acids are used for cleaning, in batteries, making fertilizers, dyes, etc.making fertilizers, dyes, etc.

Foods contain acids (vinegar & citrus Foods contain acids (vinegar & citrus fruits)fruits)

Stomach acid helps digest your foodStomach acid helps digest your food Acids in concentrated forms can cause Acids in concentrated forms can cause

severe skin damagesevere skin damage Acid vapors can damage the eyes, mouth, Acid vapors can damage the eyes, mouth,

and lungsand lungs

What are bases?What are bases?

BaseBase – a compound that increases the number – a compound that increases the number of hydroxide ions (OHof hydroxide ions (OH--) when dissolved in water) when dissolved in water

In water, bases dissociate producing OHIn water, bases dissociate producing OH-- ions ions Basic solutions (base substance + water) have Basic solutions (base substance + water) have

more hydroxide ions than hydronium ions (More more hydroxide ions than hydronium ions (More OHOH-- than H than H++))

Bases taste bitterBases taste bitter Bases feel slippery and may cause burnsBases feel slippery and may cause burns EX. baking soda, bleach, ammoniaEX. baking soda, bleach, ammonia

Strong Vs. Weak BasesStrong Vs. Weak Bases Strong bases are ionic compounds that contain Strong bases are ionic compounds that contain

hydroxide ions (OHhydroxide ions (OH--)) When dissolved in water, a strong base When dissolved in water, a strong base dissociatesdissociates (separates) forming hydroxide (separates) forming hydroxide ionsions

EX. Sodium hydroxide in waterEX. Sodium hydroxide in water

NaOH NaOH Na Na++ + OH + OH--

Weak bases do not contain hydroxide ions, but Weak bases do not contain hydroxide ions, but form them when mixed with waterform them when mixed with water EX. Ammonia and waterEX. Ammonia and water

NHNH33 + H + H22O O NH NH44++ + OH + OH--

Bases Are Useful But Can Be DangerousBases Are Useful But Can Be Dangerous

Bases are used to make soaps, to clean Bases are used to make soaps, to clean drains, to make cement, fertilize soil, etc.drains, to make cement, fertilize soil, etc.

Bases attack living tissue very quicklyBases attack living tissue very quickly In concentrated form, bases can be very In concentrated form, bases can be very

harmfulharmful Even in diluted form, some bases can be Even in diluted form, some bases can be

fairly dangerousfairly dangerous

Acids, Bases, & ElectricityAcids, Bases, & Electricity Strong acids and strong bases are good Strong acids and strong bases are good

conductors of electricity (electrolytes)conductors of electricity (electrolytes) ElectrolyteElectrolyte – a substance that dissolves in – a substance that dissolves in

water forming a solution that conducts water forming a solution that conducts electricityelectricity

EX. A solution of sulfuric acid and water EX. A solution of sulfuric acid and water conducts electric current in car batteriesconducts electric current in car batteries

What is pH?What is pH? pHpH – a number used to indicate how acidic or – a number used to indicate how acidic or

basic a solution isbasic a solution is The pH scale goes from 0 to 14The pH scale goes from 0 to 14 Solutions with a pH below 7 are acidsSolutions with a pH below 7 are acids

Lower number = stronger acidLower number = stronger acid EX. A solution with a pH of 2 is a stronger EX. A solution with a pH of 2 is a stronger

acid than a solution with a pH of 5acid than a solution with a pH of 5

What is pH?What is pH? Solutions with a pH above 7 are basesSolutions with a pH above 7 are bases

Higher number = stronger baseHigher number = stronger base EX. A solution with a pH of 13 is a stronger EX. A solution with a pH of 13 is a stronger

base than a solution with a pH of 9base than a solution with a pH of 9 Pure water has a pH of 7 and is neither acid nor Pure water has a pH of 7 and is neither acid nor

basebase

pH measures the pH measures the relative amount of Hrelative amount of H++

ions in a solutionions in a solution

NeutralizationNeutralization

To neutralize means to To neutralize means to make the pH of a solution make the pH of a solution 77

Acids and bases can Acids and bases can neutralize each otherneutralize each other

If the amounts are equal:If the amounts are equal: strong base + strong acid = neutral solutionstrong base + strong acid = neutral solution strong base + weak acid = weaker base solutionstrong base + weak acid = weaker base solution weak base + strong acid = weaker acid solutionweak base + strong acid = weaker acid solution

Neutralization ReactionsNeutralization Reactions Acids and bases react to form water and saltAcids and bases react to form water and salt

SaltSalt – an ionic compound that is a product of – an ionic compound that is a product of a neutralization reaction between an acid and a neutralization reaction between an acid and a basea base

The base provides the OHThe base provides the OH-- and the acid and the acid provides the Hprovides the H++

OHOH- - + H + H++ H H22OO The other ions from the acid and base form the The other ions from the acid and base form the

saltsalt EX. sodium hydroxide + hydrochloric acidEX. sodium hydroxide + hydrochloric acid

NaOH + HCl NaOH + HCl NaCl + H NaCl + H22OO

What is acid rain?What is acid rain? Normal rain is slightly acidic, with a pH over 5.7Normal rain is slightly acidic, with a pH over 5.7 Acid rainAcid rain – rain with a pH below 5.5 – rain with a pH below 5.5 Acid rain can harm plantsAcid rain can harm plants Acid rain can harm animals, particularly those Acid rain can harm animals, particularly those

that live in the waterthat live in the water Acid rain can damage buildings and other Acid rain can damage buildings and other

structuresstructures

How does acid rain form?How does acid rain form? Burning fossil fuels releases sulfur and nitrogen Burning fossil fuels releases sulfur and nitrogen

compounds into the atmospherecompounds into the atmosphere Sulfur dioxide reacts with moisture in clouds to Sulfur dioxide reacts with moisture in clouds to

produce sulfuric acidproduce sulfuric acid Nitrogen oxides react with moisture producing Nitrogen oxides react with moisture producing

nitric acidnitric acid The acids drop the pH of rainwater below 5.5The acids drop the pH of rainwater below 5.5 The largest natural cause of acid rain is the The largest natural cause of acid rain is the

release of sulfur dioxide by volcanoesrelease of sulfur dioxide by volcanoes

Acids & Bases - Main IdeaAcids & Bases - Main Idea

Acids and bases react in water to form Acids and bases react in water to form ions ions

Acid and base solutions contain large Acid and base solutions contain large amounts of positive or negative ionsamounts of positive or negative ions

These solutions are highly reactiveThese solutions are highly reactive When mixed, acid and base solutions can When mixed, acid and base solutions can

neutralize one anotherneutralize one another pH scale measures the strength of an acid pH scale measures the strength of an acid

or baseor base