Name:



Name: Date: Period:

Note taking Guide: Acids and Bases: Properties – Part I

Essential Questions:

← What are acids and bases?

← How can they be identified or classified?

← What are some properties of acids and bases?

← Do their strengths differ?

← How can we measure their strengths?

← How can they be neutralized?

Examples and Characteristics of

|Acids |Bases |

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Acids

1. The word acid comes from Latin word acidus meaning , ___ or .

2. Vinegar means sour wine. Vinegar is diluted .

3. Citrus fruits also have a sour or tart taste due to a different acid called .

Sweet-Tarts get their sour or tart taste from citric acid.

List of common acids:

1.

2.

3.

4.

5.

6.

Bases

1. What is the opposite of an acid?

2. The opposite would be something that can neutralize or cancel the acid.

3. The name for the opposite of acid is or basic. Let's see where the word "alkaline" came from Known for their bitter taste and slippery feel.

4. The common alkaline compounds come from the or the (no big surprise). These metal hydroxides are alkaline because they release "OH-" that can neutralize "H+" by turning it into water.

List of common bases:

1.

2.

3.

4.

5.

6.

Salts

← Created from a reaction between an aqueous acid and an aqueous base

← Ionic compounds made up from a from the base and an ________ from the acid

← Double replacement reaction

Name: Date: Period:

Note taking Guide: Classifying Acids and Bases – Part II

Arrhenius

← – produces in aqueous solutions (water).

HCl (aq) → H+ (aq) + Cl- (aq)

← – produces in aqueous solutions (water).

NaOH (aq) → Na+ (aq) + OH- (aq)

← It restricts acids and bases to water solutions.

← Only compounds with OH- can be classified as a base.

← But what about ammonia, NH3? It has the properties of a base, but would not be recognized as an Arrhenius base …

To overcome the limitations of the Arrhenius definition, chemists needed to define acids and bases in a broader, more general way.

Brønsted and Lowry.

← – donates a hydrogen ion (or H+ or proton) in a reaction.

← – accepts a hydrogen ion (or H+ or proton) in a reaction.

← The Brønsted - Lowry system involves a reaction.

← Acids and bases come in pairs.

|HCl + H2O ↔ H3O+ + Cl- |

|acid base |

HCl donates a H+ to H2O so it is the

H2O accepts the H+ from HCl so it is the

|NH3 + H2O ↔ NH4+ + OH- |

|base acid |

H2O donates a H+ to NH3 so it is the

NH3 accepts the H+ from H2O so it is the

← We know that acids and bases always come in pairs.

← How do we label the products on the right-hand side here?

|HCl + H2O ↔ H3O+ + Cl- |

|acid base |

← H3O+ is the particle formed when the original base accepts the H+ from HCl and is called the .

← Cl- is the remainder when the original acid donates the H+ from HCl and is called the .

Water – An acid or a base?

← Water “goes both ways” and can be act as an acid or a base

NH3 + H2O ↔ NH4+ + OH-

base acid c.a. c.b.

HCl + H2O ↔ H3O+ + Cl-

acid base c.a. c.b.

← – a substance that can act as both an acid and base

Let’s practice:

Label each substance as an acid or base and link the conjugate pairs.

1. NaOH (s) + H2O (l) ( Na+ (aq) + OH – (aq)

2. HCl (aq) + H2O ( H3O+ (aq) + Cl – (aq)

3. H2CO3 (g) + H2O (l) ( H3O+ (aq) + HCO3 – (aq)

4. HCl (aq) + NH3 ( NH4+ (aq) + Cl – (aq)

Arrhenius Acid and Base Practice

• Arrhenius acids produce hydrogen ions (H+) when dissolved in water. These hydrogen ions are attracted to the water molecules to produce hydronium ions (H3O+).

• Arrhenius bases produce hydroxide ions (OH-) when dissolved in water.

• Salts are ionic compounds not identified as Arrhenius bases. They result from acid-base neutralization reactions.

Identify the following compounds as either an Arrhenius acid, Arrhenius base, or salt.

HCl _________ NaOH _________ KCl _________ KOH _________

MgCl2 _________ HNO3 _________ Zn(NO3)2 _________ NaCl _________

RbOH _________ CaO _________ H2SO4 _________ AlCl3 _________

H3PO4 _________ PbSO4 _________ LiOH _________ HC2H3O2 _________

Bronsted-Lowry Acid and Base Practice

To determine whether the compound is an acid or a base using this definition, the reaction needs to be examined.

• A Bronsted-Lowry Acid is a proton (H+) donor. If the compound loses a hydrogen ion, the compound is a Bronsted-Lowry acid.

• A Bronsted-Lowry Base is a proton (H+) acceptor. If the compound gains a hydrogen ion, the compound is a Bronsted-Lowry base.

For each of the following reactions, identify the Bronsted-Lowry acid, the Bronsted-Lowry base, the conjugate acid, and the conjugate base.

Example:

NH3 + H2O ↔ NH4+ + OH-

(Base) (Acid) (Conjugate Acid) (Conjugate Base)

1. N2H4 + HSO4-1 ↔ SO4-2 + N2H5+1

Acid __________ Base ___________ Conjugate Acid _________ Conjugate Base _________

2. H2PO4-1 + H2O ↔ HPO4-2 + H3O+1

Acid __________ Base ___________ Conjugate Acid _________ Conjugate Base _________

3. HCO3-1 + H2S ↔ H2CO3 + HS-1

Acid __________ Base ___________ Conjugate Acid _________ Conjugate Base _________

Now Apply What You Learned!

1) Otis was collecting samples of Arrhenius acids and bases for a demonstration he was doing for elementary school kittens. What is an Arrhenius acid?

a. Any compound that reacts with water to produce negatively charge ions

b. Any compound that reacts with water to produce hydrogen ions

c. Any compound that reacts with water to produce hydroxide ions

d. Any compound that reacts with water to produce oxygen ions

2) Otis was collecting samples of Bronsted-Lowry acids and bases for a demonstration he was doing for elementary school kittens. What is an Bronsted-Lowry base?

a. Any compound in aqueous solution that donates a neutron

b. Any compound in aqueous solution that accepts a neutron

c. Any compound in aqueous solution that donates a proton

d. Any compound in aqueous solution that accepts a proton

3) Bronsted-Lowry acid and base reactions involve conjugate acids and bases as the products of the reactions. Given the following reaction, identify the Bronsted-Lowry acid and the conjugate acid.

NH3 + H2O ⎜⎝ NH4+ + OH-

a. The acid is H2O and the conjugate acid is NH4+

b. The acid is H2O and the conjugate acid is OH-

c. The acid is NH4+ and the conjugate acid is H2O

d. The acid is NH4+ and the conjugate acid is OH-

Now try some more problems

Name: Date: Period:

Note taking Guide: Strengths of Acids and Bases – Part III

Can you predict which the stronger acid or stronger base is?

Circle your prediction for each pairing? Are your right?

0.1 M HCl or 0.1 M HC2H3O2 0.1 M NaOH or 0.1 M NH4OH

Strength

• The strength of acids and bases is determined by the degree to which they ______________ in water.

Strong Acids

← Strong Acids and Strong Bases completely, or nearly completely, ionize in water making them excellent conductors of electricity

← Acids – Hydrochloric, sulfuric, nitric

← Bases – Sodium hydroxide, potassium hydroxide

Weak Acids

← Weak Acids and Weak Bases only partially ionize in water making them poor conductors of electricity

← Acids – Acetic, phosphoric, carbonic

← Bases – Ammonia, baking soda

Concentration

← The concentration of acids and bases is determined by the quantity of acid or base ______________ in a solution

← Strength and Concentration are very different!

Strength vs Concentration

← A very dilute strong acid or base may have little corrosive action because of the low concentration of H+ or OH- ions, while

← A very concentration solution of a weak acid or base may be very dangerous

Amphoteric Water

← We’ve talked about how water is or can be an acid, base or neutral.

← Water can react with itself to donate and accept H+ ions creating hydronium and hydroxide ions

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← Small but of H3O+ and OH– is created.

← Specifically, at 25°C, [H+] = [OH–] ≈ 1x10-7 moles/L

← Do you see any connection between this and a neutral pH of 7.0?

Kw = [H+][OH–] = (1×10-7)(1×10-7) = 1.0×10-14

This is called Kw

- Ionization constant or Ion product constant

Kw ALWAYS = 1.0 x 10-14 at 25 oC!

• This equilibrium constant is very important because it applies to all aqueous solutions — acids, bases, salts, and non-electrolytes — not just to pure water.

• Therefore if [H+] goes up [OH-] goes down

• [pic]

pH scale

← pH =

← Formula: pH = –log[H+]

– where [H+] is the concentration of hydrogen ions in moles/L

← Most solutions have a pH between 0 and 14.

← Acidic solutions have a pH

← As a solution becomes more acidic, the pH decreases.

← Basic solutions have a pH

← As a solution becomes more basic, the pH increases.

← Measures the and basicity of a solution

← Represents the relative concentration of hydrogen and hydroxide ions

← Used to simplify discussions concerning the amount of acid or base in the solution

← Uses a scale

← The pH scale uses powers of ten to express the hydrogen ion concentration.

← Because pH numbers represent log values based on the power of 10,

← pH 5 is 10 times more acidic than pH 6

← pH 4 is 100 times more acidic than pH 6

← It’s a bit like the way earthquakes are measured on the Richter scale

← 6.2-6.3 is different from 6.1-6.2

← pH values are not always

Let’s try some problems

Formula: pH = –log[H+]

****Be sure to use the EXP button and not x10power ****

Find the pH for solutions having the following [H+]:

1) 1 x 10-4 M 3) 1 x 10-11 M

2) 1 x 10-7 M 4) 1.8 X 10-5 M

5) What is the pH of a 0.15 M solution of HCl (a strong acid)?

What is the pH of these acid solutions?

6) 2 x 10-3 M HNO3 7) 3.00 X 10-7 M HNO3

Can you go the other way?

← Given a pH, can we calculate [H+] for a solution? SURE!

← Rearrange the original pH formula to get [H+] = 10–pH

← Again, use your calculator to handle the math!

← This formula uses the antilog

← To find antilog on your calculator, look for “shift” or “2nd function” and then the log button

← Don’t forget to put the negative of the pH in!

Let’s try some problems

1. If the pH of Coke is 3.12, what is [H+] ?

2. Milk has a pH of 6. What is the concentration of hydrogen ion in milk?

3. What is the [H+] in orange juice with a pH of 2.75?

pOH scale

← Would you believe, similar to pH, there is also pOH!

← pOH = the power of hydroxide

← Formula: pOH = –log[OH–]

← where [OH–] is the concentration of hydroxide ions in moles/L

← pOH looks at the perspective of a base

← Not greatly used like pH is, but it is useful for changing bases to pH

← Recall that [H+] x [OH–] = 1 x 10-14

← So pH + pOH = 14

← pOH is the reverse of pH

← a solution with a pOH < 7 is a base

← a solution with a pOH > 7 is an acid

Let’s try some problems

1. If [OH-] = 1.0 x 10 –10 M, what is the pOH?

2. What is the pOH of a 0.018 M solution of Ba(OH)2 (a strong diprotic base)?

Combined practice problems

1. What is the pH of a 0.0010 M NaOH solution?

2. The pH of an unknown solution is 6.35, what is the [H+] & [OH-]?

3. Given that a solution has a pH of 9.0, determine the [OH -] and the pOH.

4. Determine the pH of a 0.0010 M NaOH solution.

5. Find [OH-] for a solution that has a pH of 11.2.

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