chem-6-theory2 – Churner

If the pH of a 0.10 M solution of a weak acid is measured to be 4.2, what does this indicate?

The acid has completely dissociated

The acid is strong

The acid is weak and only partially dissociates

The concentration of H3O+ is 0.10 M

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Which of the following statements about weak acids is true?

Weak acids have high Ka values

Weak acids have high H3O+ concentrations at equilibrium

Weak acids establish an equilibrium where the undissociated acid remains predominant

Weak acids dissociate completely in aqueous solutions

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If an acid has a pKa of 5.4, what can be said about its relative strength?

It is weaker than an acid with pKa = 7

It is a strong acid

It is stronger than an acid with pKa = 9

It is stronger than an acid with pKa = 2

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A weak base (B) reacts with water according to the equation: B(aq) + H2O(l) ⇌ BH+(aq) + OH-(aq). What is true about this reaction?

The base donates protons to water

The base accepts protons from water, forming BH+ and OH-

The base remains undissociated in solution

The reaction goes to completion

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Which of the following correctly describes the relationship between Ka and pKa?

A larger Ka value corresponds to a smaller pKa

A smaller Ka value indicates a stronger acid

Ka and pKa are unrelated properties

A larger Ka value corresponds to a larger pKa

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What is the significance of the value pKa + pKb = 14 at 25°C?

It represents the inverse relationship between acid and base strengths in water

It does not apply to conjugate acid-base pairs

It is only valid for strong acids and bases

It is only valid in non-aqueous solutions

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What does pH measure in a solution?

The electrical conductivity

The temperature

The amount of solid dissolved

The concentration of H3O+ ions

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The pKa of lactic acid is 3.86. Which of the following statements is correct?

Lactic acid does not dissociate in water

The pH of a lactic acid solution will be lower than 7, as it is an acidic compound

The conjugate base of lactic acid is stronger than hydroxide

Lactic acid is a strong acid

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What happens to the position of equilibrium when a weak acid is added to water?

The reaction proceeds to completion

The reaction establishes a dynamic equilibrium

The equilibrium shifts completely to the left

The equilibrium shifts completely to the right

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10.

What is the role of water in the dissociation of a weak acid?

Water acts as a base, accepting a proton to form H3O+

Water does not participate in the reaction

Water is a spectator ion

Water acts as a base and accepts protons

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