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AP Chemistry Unit 8: Acids and Bases — Free with Answer Explanations | Test Practice Hub

AP Chemistry Unit 8: Acids and Bases

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Unit 8: Acids and Bases

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Question 1

A buffer solution is prepared containing $0.200 M$ acetic acid ( $C H_{3} COOH$ , $p K_{a} = 4.74$ ) and $0.200 M$ sodium acetate ( $C H_{3} COONa$ ). What is the pH of this buffer?

2.87

4.74

7.00

9.26

Question 2

Acetic acid has $K_{a} = 1.8 \times 1 0^{- 5}$ . What is the pH of a $0.10 M$ $C H_{3} COOH$ solution?

1.0

2.87

4.74

3.37

Question 3

Identify the acid-base behavior of $A l^{3 +}$ dissolved in water according to Lewis theory.

A l^{3 +}

is a Lewis base because it donates lone pairs to water.B.

A l^{3 +}

is a Lewis acid because it accepts lone pairs from water molecules.C.

A l^{3 +}

is a Brønsted–Lowry acid because it donates protons to water.D.

A l^{3 +}

has no acid-base behavior in water because it is a metal cation.

Question 4

What is the pH of a $0.010 M$ solution of $HCl$ ?

1.0

2.0

3.0

12.0

Question 5

Which of the following aqueous solutions is the strongest base?

0.10 M

N H_{3}

(

K_{b} = 1.8 \times 1 0^{- 5}

)B.

0.10 M

NaOH

0.10 M

C H_{3} N H_{2}

(

K_{b} = 4.4 \times 1 0^{- 4}

)D.

0.10 M

N a_{2} C O_{3}

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Question 6

When $HF$ ionizes in water, fluoride ion is formed. Why is $F^{-}$ a stronger base than $C l^{-}$ ?

A.Fluorine has a higher electronegativity, which makes the F–H bond stronger and F

^{-}

more reluctant to give it up.B.

F^{-}

is smaller and holds its charge density over a smaller volume, making it a better proton acceptor (stronger base).C.

F^{-}

has a higher negative charge than

C l^{-}

.D.F

^{-}

has more lone pairs available for proton donation.

Question 7

A $25.0 mL$ sample of $0.100 M$ HCl is titrated with $0.100 M$ NaOH. What is the pH at the equivalence point?

1.0

7.0

13.0

4.74

Question 8

During the titration of a weak acid (HA) with a strong base (NaOH), the half-equivalence point is reached when half the acid has been neutralized. At the half-equivalence point:

pH = 7.0

for all weak acids.B.

pH = p K_{a}

of the weak acid.C.

[A^{-}] = 0

because no conjugate base has formed yet.D.

pH

is highest at this point during the titration.

Question 9

Which of the following is the conjugate base of $H_{2} P O_{4}^{-}$ ?

H_{3} P O_{4}

HP O_{4}^{2 -}

P O_{4}^{3 -}

H_{2} O

Question 10

A buffer contains $0.300 M$ $N H_{3}$ and $0.200 M$ $N H_{4} Cl$ . What is the pH? ( $K_{b} (N H_{3}) = 1.8 \times 1 0^{- 5}$ ; $p K_{a} (N H_{4}^{+}) = 9.26$ )

9.44

9.08

4.56

9.26

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Question 11

The $K_{w}$ for water at $25° C$ is $1.0 \times 1 0^{- 14}$ . If the pOH of a solution is $3.00$ , what is the pH?

3.00

7.00

11.00

14.0

Question 12

A $100.0 mL$ sample of $0.100 M$ acetic acid ( $p K_{a} = 4.74$ ) is titrated with $0.100 M$ NaOH. After adding $50.0 mL$ of NaOH, what is the pH?

7.00

4.74

2.87

8.72