½ sheet of paper and Chemistry book out About ¼-½ a page Use your own words to describe acids and...

transcript

½ sheet of paper and Chemistry book out

• About ¼-½ a page

• Use your own words to describe acids and bases. – Give examples of acids and bases.– What is pH?

– (Mr. B Note, do this as a class discussion. K of a KWL)

½ sheet of paper and Chemistry book out

• My example: Chicken bone in vinegar.

• Acids such as Pop absorb the calcium out of bones and make the bones weak and rubbery. That’s why pop is not sold in many schools.

• Can skip pH demo and go to slide 8.

Record this orderHCl, NaOH, H2SO4, HC2H3O2,

KOH, LiOH, HNO3

• Make observations when the phenolphthalein is added.

KOH, LiOH, HNO3

• Predict what will happen when phenolphthalein is added to the last 2 solutions.

KOH, LiOH, HNO3

• Predict - What will happen when phenolphthalein is added to the last 2 solutions?

• Predict – What will happen when a solid chunk of NaOH is added to water? HCl?

KOH, LiOH, HNO3

• Explain, create a theory, about why some solutions turn pink.

Acids and Bases

Acids taste sour, become less acidic when mixed with bases.

Bases feel slippery and are bitter, become less basic when mixed

with acids.

What is the common name of a hydrogen ion?

What are the atomic parts of a hydrogen atom?

Hydrogen Ion?

What is the common name of a hydrogen ion?

What are the atomic parts of a hydrogen atom?

Proton and electron

Hydrogen Ion?Proton

What did you see at the start of all the acid formulas? (repeated next slide)

Arrhenius definition of:acid: generates [H+] in solution (HCl)

base: generates [OH-] in solution(NaOH)

Some textbooks call acids a Hydrogen donor instead of a proton donor.

HCl + H2O = H+ (aq) + Cl-(aq)NaOH(s) + H2O NaOH(aq)

NaOH(aq) = Na+(aq) + OH-(aq)

Arrhenius definition of:acid: generates [H+], Often Positive

base: generates [OH-] Often NegativeBut they are not always positive and

negative.Often but NOT ALWAYS!

For example,Sometimes they are neutral and have no charge. The can both be negative or positive, but the acid is always less

negative or the more positive.

Arrhenius definition of:acid: generates [H+], Often Positive

base: generates [OH-] Often Negative

So look at the signs and the one that is “more positive” is always the acid

because it has the [H+].

Common Bases. What do you notice common in their formulas?

Typical Acid Reaction in Water, H+ gets lonely and often combines with water.

Is water an acid or base?

So if acids begin with H and bases end with OH,What is the correct chemical formula for water?

Is water an acid or base? Both

So if acids begin with H and bases end with OH,What is the correct chemical formula for water? HOH (not H20)

Oldest or original definition:Copy the following into your powerpoint notes:

Acid Neutral Base (Water)pH 1 pH 7 pH 14 Strong Weak Weak Strong

Protons HydroxideH+ HOH OH-

H+ meet with OH- in the middle to form HOH

Bronsted-Lowry:acid: anything that donates a H+ ion

(proton donor)base: anything that accepts a H+ ion

(proton acceptor)Means a base does not have to have OH -

This definition is the most commonly used in industry.

HCl + Mg MgCl2 + H2Flashback: How do you balance this?

Lewis: acid= accept a pair of electrons

to form a covalent bondBase= e- donor

Acid with Covalent Bond: H : Cl H+ + Cl - = H:Cl H accepts e- from Cl

OH – as a base, donating an e- to H + H+ + OH - = H:OH

HCl + Mg MgCl2 + H2

Mg has formed a 2+ ion losing 2 electron H+ have each gained an electron forming H2

Remember all 3 definitions for the test:

Remember for test:When an acid and base react,

they producesalt and water

HCl + NaOH H+ + Cl- + Na+ + OH-

HCl + NaOH NaCl + HOH

Conjugate acid / Conjugate base pair:they are acid/base on the right or product side

of a reversible reaction(acid and base are reactants, Conjugates are

always Proton transfer, never OH).

Proton transfers .

acid+1 + base-

2 base-1 + acid+

acid+1 loses proton to become base-

base-2 gains proton to become acid+

. Proton transfers back

acid+1 + base-

2 base-1 + acid+

When the proton is returned, the process reverses or goes back the other direction.

Conjugate acid / Conjugate base pair:they are acid/base on the right or

product side of a reversible reaction(acid and base are reactants)

Ammonia plus water makes ammonium plus hydroxide

Note: any question that asks about conjugate means

Conjugate on the right

acid/base always means left side.

HOWEVER! If the word conjugate is NOT in the problem, then the acid or base may be on either side of the equation.

HCl (l) + H2O

(l) <--> H3O+(aq) + Cl -

Label the acid/base and conjugate acid/base

HCl (l) + H2O

(l) <--> H3O+(aq) + Cl -

Acid:_________

Base:_________

Conjugate Acid:_____________

Conjugate Base:_____________

Water reacts with the H+ in solution and forms the hydronium ion H3O+

Self-ionization of waterH2O ↔ H+ + OH-

New Concept:Water, acids, and bases have both

H+ and OH- in them at the same time.

It probably appeared that acid only has H+ but it actually has both of them. Bases also have

Remember for test:All water contains all three

of the following:Water Molecules,

Hydronium ions, and Hydroxide Ions.

Hydronium Ion is H30+

Hydroxide Ion is OH-

Know ion formula and charge.

Important. REMEMBER THIS!

ion-product constant for water (Kw):

Where have we seen that 14 before?

Important. REMEMBER THIS!

ion-product constant for water (Kw):

[concentrations] :Brackets around a element

means concentration. What do we measure concentration in?

[concentrations] :are measured

In Molarity = moles/L of Solution

(remember: solute + solvent = solution)

acidic solution = [H+] is greater than [OH-]; but

solutions have both H+ and OH- in them

(and water molecules).

[H+] of an acidic solution is greater than

1 x 10-7M

NOTES: ACIDS: [H+] > 1 x 10-7M

How concentrated is the acid?The acidity is defined most typically by

the pH value,

pH= -log[H+]

(added my me)

pH is the exponent on the 10 (made positive).

pH 2 means 1.0 x 10-2 Molarity of [H+]

[H+] pH Example

Acids 1 X 100 0 HCl

1 x 10-1 1 Stomach acid

1 x 10-2 2 Lemon juice

1 x 10-3 3 Vinegar

1 x 10-4 4 Soda

1 x 10-5 5 Rainwater

1 x 10-6 6 Milk

Neutral 1 x 10-7 7 Pure water

Bases 1 x 10-8 8 Egg whites

1 x 10-9 9 Baking Soda

1 x 10-10 10 Tums® antacid

1 x 10-11 11 Ammonia

1 x 10-12 12 Mineral Lime - Ca(OH)2

1 x 10-13 13 Drano®

The pH scale is a measure of the concentration of H+ in solutionthe higher the H+ concentration

the lower the pH number

pH means probability of Hydrogen.

The pH scale is a measure of the concentration of H+ in solutionthe higher the H+ concentration

the lower the pH number

pOH scale. Note that it is just the reverse of pH.Add pink line to your pH notes:

Acid Neutral Base (Water)pOH 14 pOH 7 pOH 1 Strong Weak Weak Strong

Protons HydroxideH+ HOH OH-

H+ meet with OH- in the middle to form HOH

Know these Equations for the test:pH + pOH = 14

pH= -log[H+]

pOH= -log[OH-]

10-pH = [H+]

10-pOH = [OH-](Discuss how to do on calculator. Point out the opposites. 2 and 4, 3 and 5.)

Examples of last slide, how to use calculator.

Given pH = 2.6, find pOH.Use pH + pOH = 14

Answer: 14 - 2.6 = 11.4

Given Molarity of H+ = [H+] = .0023 MFind pH. Use: pH= -log[H+]

Put in Calculator: -log[.0023] Answer: pH = 2.6 (2.638227)

Given pH = 2.6, find Molarity of H+ = [H+] Use10-pH = [H+]

Put in Calculator: 10-2.638227 Answer: .0023 or 2.3 x 10-3 M (or .0025)

(note: The bottom 2 equations or examples are opposites.)

Examples of last slide, how to use calculator.

Given [H+] = 2.3 x 10-3 Mfind pOH.

Put in Calculator: -log[.0023]

Gives pH = 2.6 Use pH + pOH = 14

Answer: 14 - 2.6 = 11.4 pOH = 11.4

[concentrations] ion-product constant for

water (Kw)

Important. REMEMBER THIS for

test!10 -14 / [H+] = [OH-] 10 -14 / [OH-] = [H+]

To change an acid to a base:Take away a H+ or add OH-

Take away a H+ Ex: HPO4 2- = PO4 3- + H+

Add OH- Ex: HCl + OH- = Cl- + HOH

Remember to balance charges! To change a base to an acid:

Add a H+ or take away an OH-

Ex: PO4 3- + H+ = HPO4 2-

For Conjugate Acids, take away H+

For Conjugate Bases, add H+ .

Remember to balance charges!

Monoprotic AcidDonates 1 H+

HCl = H+ + Cl-

Diprotic Acid Donates 2 H+

H2SO4 = 2H+ + SO4

Triprotic Acid Donates 3 H+

H3PO4 = 3H+ + PO4

Note: Number of H+ Donated may be different than the number of H. CH3COOH only donates 1 H+ and is Monoprotic.

If the [H+] in a solution is 1.0 x10-5 M, is the

solution acidic, basic, or neutral?

What is the [OH-] of this solution?

If the [H+] in a solution is 1.0 x10 -5 M, is the

My way:Exp is 5 so pH is 5.14-5 = 9 = pOH

[OH-] =1.0 x10 -9 M

• A solution has a [H+] of 0.0023M what is the pH? What is the pOH.

• Does this solution contain more H+ or OH-?

• (error due to rounding on calculator.)

The pH is 4.7, what is the pOH, what is the [H+] (hydrogen ion

concentration)?

The pH is 4.7, what is the pOH, what is the [H+] (hydrogen ion

concentration)?O

You try it.The pOH is 6, what is the pH and

what is the [H+]?

The pOH is 6, what is the pH and what is the [H+]?

indicator (HIn) = a weak acid / base that undergoes dissociationin a known pH range

(changes colors).[H+] + [In-]

WOD: (HIn) Something that changes color to indicate a pH level.

Color Indicators

Acid dissociationconstant (Ka): is the ratio of the concentration of the dissociated (or ionized) form of an acid to

the concentration of the undissociated (nonionized) form.

Note: Dissolved Ions on top. Undissolved on bottom.

WOD in 2 slides.

Acid dissociationconstant (Ka):

HCl H+ + Cl-

The HCl and H+ + Cl- exist in the water at the same time.

Acid dissociationconstant (Ka): is the ratio of the

molarity of the ions over the molarity of the whole acid. High

number means strong acid.For WOD: Also Copy equation

Strong acids/bases completely dissociate in water, so do not

have Ka values. .Do not confuse . Ka and Kw. .

Ka: How Strong . Kw: How Much .

Weak acids/bases only partly dissociate in water

If Ka value exists, then the reaction is

reversible and the right side is a

conjugate acid/base pair.

Weak acids have small Ka values.

The stronger the weak acid, the larger the

Ka value, the more of the solid that

dissolves.

The words concentrated and dilute indicate

how much of an acid or base is dissolved in solution.

(Molarity)

Not if it is a strong or weak acid/base.

The words concentrated and dilute indicate

how much of an acid or base is dissolved in solution.

(Molarity)

Not if it is a strong or weak

a strong acid can be concentrated or diluted.

A 0.100M solution of methanoic acid is only partially ionized. The [H+] is 2.0 x 10-3 M. What is the acid dissociation constant (Ka) of methanoic

1. What are 5 equations from this chapter (pH and pOH)?

2. What is the pH and pOH of a 0.000316M solution of HCl?

3. In your own words describe acids and bases (2-3 sentences). (Give examples, pH…)

4. What is the pH and pOH of a 0.00055M solution of NaOH?

1.) pH + pOH = 14 pH= -log[H+]

pOH= -log[OH-]10-pH = [H+]

10-pOH = [OH-]2.) pH=3.5 pOH= 10.5

3.) Individual Descriptions 4.) pH=3.25 pOH= 10.75

Any rain that falls with a pH below 5.6 is considered acid rain

Salts = compoundsconsisting of an anion

from an acid and a cation from

a base. Ex: HCl = H+ + Cl-

NaOH = OH- + Na+

Cl- is an Anion Na+ is a Cation

Put the anion and cation together to form a salt.

neutralization reactionsacids and bases react in water

to produce a salt and water (what kind of reaction is this?)When acids and bases react

in “equal” quantities to make neutral water.(Equal H+ and OH-)

Equivalence point when the number of moles

of hydrogen ions equals the

number of moles of hydroxide ions (neutralized)

What is pH, pOH, [H+], [OH-]?

How many moles of hydrochloric acid are

required to neutralize 0.50 mol of

calcium hydroxide?

How many moles of hydrochloric acid are required to neutralize 0.50 mol ofcalcium hydroxide?

Step 1.) Make sure equation is balanced.Step 2.) List known. Step 3.) List Unknown.Step 4.) Use dimensional analysis to change known to unknown (multiply by molar ratio.

calcium hydroxide?

calcium hydroxide?=1

You try it!How many moles of

calcium hydroxide are required to neutralize 1.37

mol of hydrochloric acid?

How many moles of calcium hydroxide are

hydrochloric acid?

TitrationAdding a known amount of base or

acid to an unknown to find the pH of the unknown.

Uses:Equivalence point, End

Point, Neutralization, and

Indicators

TitrationA titration is done to find the

molarity of an unknown solution by neutralization . A pH indicator that changes color at 7 is added. A standard solution of a base such as

Ca(OH)2 is added to an acid until the solution changes color. The known pH of the added base is used to find

the starting pH of the acid.

End Point The point at which the indicator changes color

during a titration.

TitrationShow titration videos

Intro:

http://www.youtube.com/watch?v=3iuVXHxyB1k&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

2 short samples.

http://www.youtube.com/watch?v=g8jdCWC10vQ&safety_mode=true&persist_safety_mode=1&safe=active

http://www.youtube.com/watch?v=s1TCH3Vj2RY&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

Optional. 6min http://www.youtube.com/watch?v=YDzzMcrdyB4&feature=grec_index&safety_mode=true&persist_safety_mode=1&safe=active

Example of caluculations http://www.youtube.com/watch?v=BllRQAc76Y0&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

Find the moles needed to make the solution reach the equivalence point

3 steps to solve a titration:1. Find moles of known or

added H+ or OH-

L x M = n (known) 2. Find moles of unknown.

Use equivalent point: moles of unknown = moles

of known3. Find molarity of

unknown.n / L = M (unknown)

A 33-mL solution of HCl is completely neutralized by 22-mL of 1.0M Ca(OH)2.

What is the concentration (molarity) of the HCl

solution?

A 33-mL solution of HCl is completely neutralized by 22-mL of 1.0M Ca(OH)2. What is the concentration (molarity) of the HCl solution?

A 50-mL solution of Ca(OH)2 is completely neutralized by 25-mL of 1.0M HCl. What is the concentration (molarity)

of the HCl solution?

A 50-mL solution of Ca(OH)2 is completely neutralized by 25-mL of 1.0M HCl. What is the concentration (molarity)

of the calcium hydroxide solution?

A 50-mL solution of Ca(OH)2 is completely neutralized by 25-mL of 1.0M HCl. What is the concentration (molarity) of the calcium hydroxide solution?

Buffer is a solution in which the pH remains

relatively constantwhen small amounts of acid or base are added.

buffer capacity is the amount of acid or base

that can beadded to a buffer solution

before a significant change in pH occurs.

½ sheet of paper and Chemistry book out About ¼-½ a page Use your own words to describe acids and...

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