Acids and Bases

Acids and Bases

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Multiple Choice

Acids are proton __________

• acceptors

• positive

• donors

• haters

Multiple Choice

What pH do acids have?

• less than 7

• more than 7

• 0

• 7

Multiple Choice

Bases are proton __________ and taste _________.

• donors, bitter

• acceptors, sour

• acceptors, bitter

• donors, sour

Multiple Choice

Bases have a pH of ___________ and ___________ acids.

• less than 7, catalyze

• greater than 7, neutralize

• greater than 7, catalyze

• less than 7, neutralize

Multiple Choice

What happens to strong acids and bases in aqueous solution?

• 50% dissociation into ions

• nothing

• they neutralize each other

• 100% dissociation into ions

Multiple Choice

What is the pH scale's range?

• 0-13

• 1-4

• 7-14

• -1-14

Acids and Bases

By Mihir Paranjape

Acids

Acids release H⁺ (protons) in solutions.

HCl > H⁺ + Cl^-​

• Sour Taste

• Electrolytes: Can conduct electricity.

• React with Metals

• Turn Blue litmus Red

• Have pH <7​

Bases

Bases release OH^- in solutions.

NaOH > Na⁺ + OH^-​

• Bitter Taste

• Electrolytes: Can conduct electricity.

• Soapy Touch​

• React with Acids

• Turn Red litmus Blue

• Have pH >7​

pH

pH = -log [H⁺]

• pH is also called the power of Hydrogen.

• [H⁺] = concentration of H⁺ in M (moles/L)​

• It is a number between 0 and 14

• Low pH means more [H⁺] - stronger acid.

• Higher pH means lower [H⁺] - weaker acid.

• Acids have pH 0-7​

pH

pH = -log [H⁺]

​Calculate pH of a 0.001 M HCl solution?

We know that HCl splits into H+ and Cl- ions.

HCl is a strong acid and therefore [H+] =[HCl] = 0.001 M

​

pH = -log (0.001) = -(-3) = 3​

pH

pH = -log [H⁺]

​Calculate pH of if [H+] = 2.31 x 10^-5 M

​

pH = -log (2.31 x 10^-5) = -(-4.64) = 4.64​

Multiple Choice

If a solution has a [H⁺] of 9.3x10^-11, what is the pH?

• 10.0

• 4.0

• 3.5

• 8.2

pOH

pOH = -log [OH^-]

• pOH is also called the power of OH.

• [OH^-] = concentration of OH^- in M (moles/L)​​

• It is a number between 0 and 14

• Low pOH means more [OH^-] - stronger base.

• Higher pH means lower [OH^-] - weaker base.

• Bases have pH 7-14

Multiple Choice

If the [OH-] of a solution is 2.7 x 10^-4 mol/L the pOH of the solution is

• 10.44
• 3.56
• 1.00
• -4.43

pH + pOH = 14

• You can calculate one from the other using this equation.

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E.g. Calclate the pOH if pH = 4.64

​pH + pOH = 14

4.64 + pOH = 14​

pOH = 14-4.64 = 9.36​

pH + pOH = 14

• You can calculate one from the other using this equation.

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E.g. Calclate the pH if [OH^-] = 5.67 x 10^-6 M

Since OH- is given, we can calculate pOH = -log( 5.67 x 10^-6 )

pOH = 5.25​

pH + pOH = 14​

pOH = 14-5.25 = 8.75​

Multiple Choice

A  pH and a pOH will add up to:

• 0
• 7
• 14
• 1.0 x 10^-14

Multiple Choice

if the [H+] of a solution is 8.4 x 10^-3 mol/L the pOH of the solution will be

• 2.08
• 11.92
• 1.02
• 12.98

Multiple Choice

If the pH of a solution is 5.6 the pOH is

• 6.5
• 12.4
• 8.4
• 5.6

[H⁺] = 10 ^-pH

If you know the pH, you can calculate the [H⁺] concentration in M.

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E.g. Calculate the [H⁺] if pH is 3.4?

​[H⁺]​ = 10 ^-3.4​ = 0.000398 M or 3.98 x 10^-4 M

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Calculate ​the [H⁺] if pOH is 3.4?

First calculate the pH = 14 - 3.4 = 10.6

Next ​[H⁺]​ = 10 ^-10.6​ = 2.51 x 10^-11 M

[OH^-] = 10 ^-pOH

If you know the pOH, you can calculate the [OH^-] concentration in M.

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E.g. Calculate the [OH^-] if pOH is 8.9?

​[OH^-]​ = 10 ^-8.9​ = 1.26 x 10 ^-5 M

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Calculate ​the [OH^-] if pH is 2.3?

First calculate the pOH = 14 - 2.3 = 11.7

Next ​[OH^-]​ = 10 ^-11.7​ = 2 x 10^-12 M

Multiple Choice

The pH of a solution is 8.43. What is the [H⁺]concentration?

• 3.7 x 10 ^-9

• 1.0 x 10^-8.43

• 2.7 x 10^-6

• 1.0 x 10^-14

Multiple Choice

If a solution has a pOH of 3.7 the [OH-] of the solution is

• 5.0 x 10^-11

• 2.0 x 10^-4

• 10.3

• 14

Multiple Choice

Oranges have a [H⁺] of 1.7 x 10^-2 M. Their pOH is

• 1.77

• 12.23

• 10.91

• 3.09

Multiple Choice

What is the [H+] if the pH is 4.0?

• 1.0 x 10^-10 M

• 1.0 x 10^-14 M

• 1.0 x 10^-4 M

• 1.0 x 10^-7 M

Titration Curves

If you start with an Acid, you will start with a low pH.

If you now add a Base to this, the Base will react with the acid thereby reducing the [H+] and increase pH slowly.

This will happen till the solution reaches a pH of 7 at which point it is neither an acid or a base, this is called the end point or equivalence point.

The Graph of pH vs volume added is called a Titration curve.​

Multiple Choice

What is the end point or equivalence point of this Titration?

• 10 mL

• 20 mL

• 30 mL

• 40 mL

Multiple Choice

What is the volume of NaOH added at the end point of this titration?

• 20

• 40

• 60

• 80

Multiple Choice

How much HCl has to be added to the base to complete the titration?

• 10

• 40

• 50

• 60

Strengths of Acids and Bases

Benchmark: SC.912.P.8.11

Student objective:

• Use experimental data to illustrate and explain the pH scale to characterize acid and base solutions;

• Compare and contrast the strengths of various common acids and bases;

• Measure pH using various tools; for example, litmus paper pH indicators and pH probe

Multiple Choice

A(n) _____ is a substance that produces hydrogen ions in solution.

• base

• acid

• indicator

• salt

Multiple Choice

Which of the following statements about acids is NOT true?

• acids taste sour

• acids are corrosive

• acids form hydroxide ions in a solution

• many foods contain acids

Multiple Choice

A(n) ______ is an organic compound that changes color in acid.

• catalyst

• base

• indicator

• salt

Multiple Choice

Any substance that forms hydroxide ions in solution is a(n) ______.

• acid

• salt

• indicator

• base

Multiple Choice

Which of the following statements about bases is NOT true?

• Pure, undissolved bases are often crystalline solids.

• bases form when acids react with metals

• bases in solution feel slippery

• bases form hydroxide ions in solution

Open Ended

In yesterday's lab, we discussed and tested the pH levels of different substances. Give three examples of substances that are acidic and basic. Then explain what characteristics make those substances acidic or basic.

Reminder:
- pH is a measurement that is used to rate the strengths of acids and bases, indicating positive hydrogen ions or H+ ions.

Scenario: A swimming pool and spa owners must find out whether the water is too acidic or basic.

​Turn and Talk - Why is it important for these owners to have the proper pH?

1. What determines the strength of an acid or a base?
2. How effectively do different acids and bases conduct electricity?
3. What is the difference between strength and concentration?

​Today's Essential Questions

​Important vocabulary to know:
Ionization - the process in which some molecules dissolve in water and separate into charged particles.

• Depends on the degree to which acid or base particles form into ions in water

• Strong acids ionize upon dissolving in water.

• In weak acids, a small fraction of ionization occurs in water.

Determining the Strength of an Acid

• Ions in a solution conduct electric currents.

• More ions = More conductivity

• Less ions = Less conductivity

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Effectiveness of acids and bases when conducting electricity.

Multiple Choice

A _____ will ionize only to a small extent because its molecules have a strong hold on their H atoms.

• weak acid

• strong acid

• weak base

• strong base

Group Discussion Question

What do you think is the difference between the terms strength and concentration?

Strength vs. Concentration

Remember: Strength refers to the degree to which an acid or base ions are formed in water.

Concentration - refers to how much acid or base is present in a solution.

Go to Google classroom and complete the strengths of acids and bases reinforcement.

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Today's Activity

Open Ended

Based on today's lesson, what did you learn today? What did you like or dislike about today's lesson?