CHEM 120B MIDTERM 3 PRACTICE

Acid Base Concept

100

Name all strong acids!

HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄

200

Name all strong bases

LiOH, NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂

300

Write formula for pK_a, pK_b, K_a, K_b, K_w and %ionization. (WRITE UNITS if they apply)

Check with SI Leader Amb! :D

400

What is a buffer, and how would you make a buffer using a weak acid solution with NaOH?

A Buffer is a solution containing a major species of a conjugate weak acid/base pair.

Add NaOH to neutralize HALF of the weak acid to make a buffer.

500

Draw titration curves for

- Titration of Strong Acid with a Strong Base

- Titration of a Strong Base with a Strong Acid

- Titration of a Weak Acid with a Strong Base

- Titration of a Weak Base with a Strong Acid

- (Bonus: 100 more points!) Titration of a Weak Base with a Weak Acid

Check with SI leader Amb! :D

pH Calculations

100

Calculate pH given concentrations of OH^- or H₃O⁺ OR Calculate H₃O⁺ given pOH

[H₃O⁺] = 7.49•10^-6

[OH^-] = 8.53•10^-7

[H₃O⁺] = 7.49•10^-6

[OH^-] = 6.46•10^-6

pOH = 2.9

[H₃O⁺] = 7.49•10^-6 pH = 5.17

[OH^-] = 8.53•10^-7 pH = 7.93

[H₃O⁺] = 1.23•10^-6 pH = 10.91

[OH^-] = 6.46•10^-6 pH = 8.81

pOH = 2.9 [H₃O⁺] = 7.94•10^-12

200

What is the [H₃O⁺], [OH^-], pH, and pOH of 0.15 NaOH at room temp?

[H₃O⁺] = 6.7•10^-14M

[OH^-] = 0.15M

pH = 13.18

pOH = 0.82

300

What is the pH and percent ionization of a 0.696M solution of HCN?

K_a = 4.9•10^-10

pH = 4.73

%ion = 0.00266%

400

What is the pH and percent ionization of a 0.749M solution of F^-? ^{(READ CAREFULLY)}

K_a of HF = 3.5•10^-4

pH = 8.68

%ion = 0.000601%

500

what is the pH and percent ionization of 0.214M solution of CH₃COO^-?

K_a CH₃COOH = 1.8•10^-5

^{(READ CAREFULLY!)}

pH = 9.04

%ion = 0.00509%

Buffers

100

What is the pH of a buffer solution that is 0.24M NH₃ and 0.20M NH₄Cl?

NH₄⁺ Ka = 5.6•10^-10

pH = 9.33

200

Determine the pH of a Buffer solution that is comprised of 0.200M Lactic Acid and 0.500M of Lactate. K_a Lactic Acid = 1.38•10^-4​

​​​

pH = 4.25

Titrations!

100

A 50.0mL solution of 0.100M HCl is titrated with 0.100M NaOH. Calculate pH after addition.

0mL, 25mL, 50mL, 60mL

0mL) pH = 1.00

25mL) pH = 1.48

50mL) pH = 7.00

60mL) pH = 12.00

200

100.0 mL solution of 0.100M NH₃ is titrated with 0.100M HClO₄. Calculate the pH after the following additions of HClO₄.

Kb NH3 = 1.8•10-5

200mL and 250mL

pH = 1.48

pH = 1.37

300

100.0 mL solution of 0.100M NH₃ is titrated with 0.100M HClO₄. Calculate the pH after the following additions of HClO₄.

K_b NH₃ = 1.8•10^-5

0mL and 100 mL!

0mL) pH = 11.13

100mL) pH = 5.28

400

100.0 mL solution of 0.100M NH₃ is titrated with 0.100M HClO₄. Calculate the pH after the following additions of HClO₄.

K_b NH₃ = 1.8•10^-5

25mL and 150 mL!

25mL) pH = 9.73

150mL) pH = 1.70

500

A 800.0mL solution of 0.200M CH₃NH₂ is titrated with 0.800M HI. Calculate the pH after the following additions of HI solution. pK_b = 3.36

0mL, 50mL, 100mL, 150mL, 200mL, and 250mL

0mL) pH = 11.97

50mL) pH = 11.12

100mL) pH = 10.64

150mL) pH = 10.16

200mL) pH = 5.72

250mL) pH = 1.42

RANDOM TRIVIA

100

What is the tennis score for (0:0)?

"Love All"

200

What is the condensed electron configuration of cobalt ion, Co³⁺ ? 

[Ar] 4s⁰ 3d⁶  

300

What language has the most native speakers worldwide?

Mandarin Chinese

400

Riddle: The more you take, the more you leave behind, what am I?

Footsteps

500

What's the rarest blood type?

AB-negative