CHEM 1A03 Lecture Notes - Lecture 7: Conjugate Acid, Lewis Acids And Bases, Amphoterism

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CHEM 1A03 Full Course Notes

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Fun facts: early qualitative tests to distinguish between acids and bases were done by taste, acidic = sour. Arrhenius theory / electrolyte theory: acids generate protons, bases produce hydroxide, theory is applicable to protic acids and metal hydroxides in water, but excludes many compounds. Product is a conjugate base: base = proton acceptor. Product is a conjugate acid: water is amphoteric: behaves as both an acid or a base. Lewis theory: acid = electron pair acceptor, base = electron pair donor. Acid and base equilibrium constants: based on the reactions of acids and bases with water, ka - acid disassociation constant, kb - base disassociation constant. Strong and weak acids and bases: strong acids/bases are species that completely dissociate in water to generate stochiometric amounts of h3o+ or oh, products dominate, weak acids/bases undergo only partial disassociation in water, reactants dominate. Strong acids (memorize): hcl, hbr, hi, hclo4, hno3, h2so4. Strong bases: group i + ii hydroxides, hydrides, and oxides.

Related Questions

For conjugate acid-base pairs, how are Ka and Kb related?

Consider the reaction of acetic acid in water:

CH₃CO₂H (aq) + H₂O (l) ⇌ CH₃CO₂⁻ (aq) + H₃O⁺ (aq) where Ka = 1.8 × 10⁻⁵

Which two bases are competing for the proton?
Which is the stronger base?
In light of your answer to part b. why do we classify the acetate ion (CH₃CO₂⁻) as a weak base? Use an appropriate reaction to justify your answer.
In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH₃ is a weak acid.

To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1× 10⁶, calculate Kb for the conjugate base of this strong acid.

Why do conjugate bases of strong acids have no basic properties in the water?

List the conjugate bases of the six common strong acids.

To tie it all together, some instructors have students think of Li⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Sr²⁺, and Ba²⁺ as the conjugate acids of the strong bases LiOH, KOH, RbOH, CsOH, Ca(OH)₂, Sr(OH)₂, and Ba(OH)₂. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acidic properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a_____base. The conjugate acid of a weak base is a_____acid. The conjugate base of a strong acid is a_____base. The conjugate acid of a strong base is a_____ acid. ( Hint: Weak gives you weak and strong gives you worthless.)

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QUESTION 1

Which of the following substances is most acidic?

		Cowâs milk - pH 6.6
		Apple juice - pH 3.0
		Tomato juice - pH 4.5
		Distilled water - pH 7.0

2 points

QUESTION 2

A buffer is a substance that converts:

Alkaline solutions to neutral solutions.

Acidic solutions to alkaline solutions.

Strong bases or acids to weak bases or acids.

Acidic solutions to neutral solutions.

QUESTION 3

How does a solution of pH 7 compare to a solution of pH 10?

		pH 7 has more OH^- ions
		pH 7 is more basic
		pH 7 has a higher pH
		pH 7 has more H⁺ ions

2 points

QUESTION 4

According to the Arrhenius Theory of acids and bases, a base is:

A substance that decrease the amount of hydroxide ions present.

A substance that increases the amount of hydroxide ions present when it is dissolved in water.

A substance that increase the amount of hydrogen ions present.

A substance that increases the amount of hydrogen ions present when it is dissolved in water.

QUESTION 5

Which of the following are true regarding acid-base titrations?

		They are used to determine the concentration of an unknown acid or base.
		The acid or the base must be a standard solution with a known concentration
		The standard solution is titrated into the chemical with the unknown concentration.
		All of the above are true regarding acid-base titrations.

2 points

QUESTION 6

Which of the following is not an example of a neutralization reaction?

HCl + NaOH NaCl +H₂O

2 NaOH + H₂CO₃ Na₂CO₃ +2 H₂O

H₂SO₄ + 2 NH₄OH (NH₄)₂SO₄ + 2 H₂O

2 AgNO₃ + Zn 2Ag +Zn(NO₃)₂

QUESTION 7

Which acid base theory defines an acid as a proton donor and a base as a proton acceptor?

		Arrhenius Theory
		Bronsted-Lowery Theory
		Conjugate Pairs Theory
		Lewis Theory

2 points

QUESTION 8

The Arrhenius Theory states that acid-base reactions create a solution composed of a water and a salt. This is because mixing an acidic and basic solution together yields:

A neutral solution

A solution with a pH at or near 7

Both A and B are correct

QUESTION 9

Which of the following correctly defines a standard solution?

		A solution which always has the same molecular geometry.
		A solution in which the concentration is precisely known.
		A solution in which the volume is precisely known.
		A solution which always has different levels of solutes and solvents.

2 points

QUESTION 10

Acids naturally present in food are generally safe to eat because they are usually:

		Concentrated
		Dilute
		Weak
		Strong

None of the above are correct

CHEM 1A03 Lecture Notes - Lecture 7: Conjugate Acid, Lewis Acids And Bases, Amphoterism

CHEM 1A03 Full Course Notes

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