Chapter 10Chapter 10

Acids and basesAcids and bases

Identifying features of acidIdentifying features of acid

Sour tastes ( ex. lemon juice, vinegar)Sour tastes ( ex. lemon juice, vinegar)

Conducts electricity when in liquid Conducts electricity when in liquid (electrolyte) (electrolyte)

React with a base to form water & a React with a base to form water & a salt (neutralization rxn) salt (neutralization rxn)

A salt is the ionic product of an acid A salt is the ionic product of an acid base rxnbase rxn

Identifying features of acidIdentifying features of acid

Acids react with certain metals to Acids react with certain metals to form Hform H22 gas. gas.

Look at table J.Look at table J.

All metals that are above Hydrogen All metals that are above Hydrogen will react with it, but those below will react with it, but those below wont.wont.

Cause indicators to change colors Cause indicators to change colors (more on this later)(more on this later)

BasesBases

Bitter taste (bleach, ammonia, soap)Bitter taste (bleach, ammonia, soap)

Slippery or soapy feelingSlippery or soapy feeling

Conduct electricity in liquid Conduct electricity in liquid (electrolyte)(electrolyte)

React with acids to form water and a React with acids to form water and a saltsalt

Cause indicators to change colors Cause indicators to change colors (more on this later)(more on this later)

What makes an acid an acidWhat makes an acid an acid

Scientists had known for a long time Scientists had known for a long time common features of acids, but they common features of acids, but they didn’t know why an acid displayed didn’t know why an acid displayed those featuresthose features

What was it that made an acid an What was it that made an acid an acid.acid.

Arrhenius Arrhenius Svante Arrhenius proposed that an Svante Arrhenius proposed that an acid is any substance that when acid is any substance that when mixed with water will give off a mixed with water will give off a Hydrogen ion.Hydrogen ion.

HCl ----HCl ---- H H++ & Cl & Cl--

HNOHNO22---- H H++ & NO & NO22--

HH22SOSO44 2H 2H++ & SO & SO442-2-

Not everything with a hydrogen is Not everything with a hydrogen is an acidan acid

Methane CHMethane CH44

& Sugar C& Sugar C66HH1212OO66 are molecules with are molecules with a hydrogen that are not acids.a hydrogen that are not acids.

Molecules with H are only acids if the Molecules with H are only acids if the molecule is ionic, but if the molecule molecule is ionic, but if the molecule is covalent the H is not released in is covalent the H is not released in liquid.liquid.

So what makes a hydrogen acidic?So what makes a hydrogen acidic?When a HWhen a H++ ion is in water it cannot remain ion is in water it cannot remain there alone.there alone.

It will quickly react with water to form HIt will quickly react with water to form H3300++

This new molecule is called a hydronium This new molecule is called a hydronium ion.ion.So all the acidic substances act the way So all the acidic substances act the way they do, bc of their Hydronium ions. they do, bc of their Hydronium ions.

BasesBasesAccording to the Arrhenius theory a base According to the Arrhenius theory a base is any substance that increases the is any substance that increases the amount of OHamount of OH-- (hydroxide) ions in water. (hydroxide) ions in water.

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

KOH KOH K K++ & OH & OH--

Ca(OH)Ca(OH)22 Ca Ca+2+2 & 2OH & 2OH--

The properties of a base is because of the The properties of a base is because of the OH OH

ExceptionException

NH3 (ammonia) is classified as a NH3 (ammonia) is classified as a base even though it lacks OH.base even though it lacks OH.

But upon closer examination we find But upon closer examination we find NH3 does create OHNH3 does create OH-- ions. ions.

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

Table K & LTable K & L

On your reference table the common On your reference table the common acids and bases you need to know acids and bases you need to know for the regents are listed. for the regents are listed.

Strength of acids and basesStrength of acids and bases

Hydrocloric acid --- very dangerousHydrocloric acid --- very dangerous

Citric acid ----Found in plantsCitric acid ----Found in plants

Boric acid--- used in eye washesBoric acid--- used in eye washes

Strenghts of acidsStrenghts of acids

A very strong acid will have all of its A very strong acid will have all of its Hydrogen’s leave the compound and Hydrogen’s leave the compound and enter the waterenter the water

A very weak acid will only have a few A very weak acid will only have a few of its H’s leave the compound and of its H’s leave the compound and enter the waterenter the water

ReactionsReactions

As we saw on from table J acids react As we saw on from table J acids react with most metals to release Hwith most metals to release H22 gas. gas.

We also have a Neutralization We also have a Neutralization reaction. This is when an acid and reaction. This is when an acid and base react to balance each other out.base react to balance each other out.

Neutralization reactionsNeutralization reactions

HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl

Acid + Base Acid + Base Water + salt Water + salt

Neutralization reactionNeutralization reaction

The H of acid combines with the OH The H of acid combines with the OH of base to create Hof base to create H22OO

The left over molecules combine to The left over molecules combine to make a salt.make a salt.

Neutralization reactionNeutralization reaction

HNO3 + KOH HNO3 + KOH ??

Acid + Base Acid + Base Water & salt Water & salt

H & OH combine to make HH & OH combine to make H22OO

NONO33 & K combine as the salt = KNO & K combine as the salt = KNO3 3

Neutralization reactionsNeutralization reactions

HNO3 + NaOH HNO3 + NaOH

HCl + KOHHCl + KOH

  H3PO4 + 3 NaOH H3PO4 + 3 NaOH

PH ScalePH Scale

In chemistry we measure the In chemistry we measure the concentration of an acid or base on a concentration of an acid or base on a scale of 1-14scale of 1-14

This is called the PH scale. This is called the PH scale.

On the PH scale 0-7 is acidic. The lower On the PH scale 0-7 is acidic. The lower the number the more acidic. (More the number the more acidic. (More HH++))

7-14 is basic. The higher the number 7-14 is basic. The higher the number the more basic (more OHthe more basic (more OH--))

7 is neutral. (Pure water)7 is neutral. (Pure water)

PH ScalePH Scale

If bananas have a PH of about 5 & If bananas have a PH of about 5 & milk is about 6, which is more acidic?milk is about 6, which is more acidic?

Ammonia has a PH of 11, soap has a Ammonia has a PH of 11, soap has a PH of 12. Which has more OHPH of 12. Which has more OH-- Ions Ions

IndicatorIndicator

An indicator is a chemical that will An indicator is a chemical that will change colors in order when placed change colors in order when placed in a certain PH.in a certain PH.

They are used to indicate what the They are used to indicate what the PH of a liquid is.PH of a liquid is.

PH ScalePH Scale

Each number moved on the PH scale Each number moved on the PH scale is increased 10 times more acidic, or is increased 10 times more acidic, or basic.basic.

Example if HCl is a ph of 1Example if HCl is a ph of 1

And Acetic acid is a ph of 2And Acetic acid is a ph of 2

How much more acidic is HCl then How much more acidic is HCl then acetic acid? acetic acid?

PHPH

If 1 number on the scale is 10 times If 1 number on the scale is 10 times more acidic (or basic)more acidic (or basic)

Then 2 numbers is 100 times more Then 2 numbers is 100 times more acidic (or basic)acidic (or basic)

And 3 numbers is 1000 times moreAnd 3 numbers is 1000 times more

ExampleExample

How much more basic is a solution of How much more basic is a solution of PH 10 then a solution of PH 8? What PH 10 then a solution of PH 8? What about PH 9? PH 7?about PH 9? PH 7?

How much more acidic is ph 6 then How much more acidic is ph 6 then 7?7?

ExampleExample

A truck carrying nitric acid overturns A truck carrying nitric acid overturns and spills its content in a neerby and spills its content in a neerby lake, that had a PH of 8.lake, that had a PH of 8.

After the spill the lake is 1000 times After the spill the lake is 1000 times more acidic.more acidic.

What is the new PH? What is the new PH?

TitrationTitration

In a neutralization reaction there In a neutralization reaction there must be a 1:1 ratio of Hmust be a 1:1 ratio of H++ to OH to OH--

Using this knowledge we can Using this knowledge we can determine the concentration of an determine the concentration of an acid by only knowing the acid by only knowing the concentration of the base it reacted concentration of the base it reacted with.with.

Titration Titration

For exampleFor example

If I have 1 L of 1 molarity acid I will If I have 1 L of 1 molarity acid I will need 1 L of 1 molarity base to cancel need 1 L of 1 molarity base to cancel it out.it out.

What about if I only had 2 Molarity What about if I only had 2 Molarity base, how much would I need to base, how much would I need to cancel out the acid?cancel out the acid?

TitrationTitration

I would only need half a liter of the 2 I would only need half a liter of the 2 Molarity base to cancel out all the Molarity base to cancel out all the acid.acid.

TitrationTitration

The formula for titration is found on The formula for titration is found on your reference table.your reference table.

It is MIt is Maa * V * Vaa = M = Mbb * V * Vbb

This mean Molarity of acid X volume This mean Molarity of acid X volume of acid = Molarity of base X volume of acid = Molarity of base X volume of baseof base

TitrationTitration

What is the concentration of sulfuric What is the concentration of sulfuric acid if 50 mL of .25 Molarity KOH are acid if 50 mL of .25 Molarity KOH are needed to neutralize 20 mL of the needed to neutralize 20 mL of the acid?acid?

MMaa * V * Vaa = M = Mbb * V * Vbb

X * (20) =(.25) * (50)X * (20) =(.25) * (50)

X is the Molarity of sulfuric acidX is the Molarity of sulfuric acid

Bronsted Lowry theoryBronsted Lowry theory

There is another theory of acids & There is another theory of acids & bases besides Arrhenious called the bases besides Arrhenious called the Bronsted Lowry theory.Bronsted Lowry theory.

The regents just calls it the The regents just calls it the alternative theory.alternative theory.

Bronsted Lowry theoryBronsted Lowry theory

According to this theory an acid is According to this theory an acid is anything which is a Hanything which is a H++ donor donor

And a base is anything that accepts And a base is anything that accepts HH++