Chemical Jeopardy 2 NEW

Acids Base 1

100

1. What is a Bronsted-Lowry Acid?

2. What is a Bronsted-Lowry base?

1. A proton donor

2. A proton acceptor

200

What is an amphiprotic species? Give a general or specific example.

Species that can act as acid or base. Examples include partially deprotonated polyprotic acids such as HS^-

300

Decide whether aqueous solutions of the salts:

1. Na₂CO₃
2. AlCl₃
3. KNO₃

are acidic, neutral or basic

1. basic
2. acidic
3. neutral

400

1. What is the pOH if [H₃O⁺] = 1 x 10^-5?

2. What is the relationship between pH and pOH?

1. pH = 5.0, pOH = 9.0

2. pH + pOH = 14.0

500

1. What is the pK_a of an acid with a K_a = 1 x 10^-4?

2. What is the pK_b of the conjugated base of this acid?

1. pK_a = 4.0

2. pK_b= 14.0 - 4.0 = 10.0

Acids Bases 2

100

1. Write the chemical formula for the conjugate acid of the base pyridine C₅H₅N₅
2. Write the formula for the conjugate base of the acid HIO₃.

1. C₅H₅N₅H⁺
2. IO₃^-

200

Select the stronger acid or base in the following pairs:

1. HF (pK_a = 3.45) or HIO (pK_a = 10.64)
2. C₆H₅NH₂(pK_b = 9.37) or (CH₃)₃N (pK_b = 4.19)

1. HF
2. (CH₃)₃N

300

For each of the following pairs, predict and explain which acid is stronger:

1. H₂S and HCl
2. HBrO₂ and HBrO₃
3. H₂SO₃ and H₂SeO₃

1. HCl (Cl is more electronegative than S)
2. HBrO₃ (greater number of O atoms)
3. H₂SO₃ (S is more electronegative then Se)

400

For each of the following pairs, predict and explain which base is stronger:

1. ClO₂^- and ClO^-
2. S^2- and Te^2-
3. AsO₃^3- and PO₃^3-

1. ClO^- (conjugate base of the weaker acid, HClO)
2. S^2-(conjugate base of the weaker acid, H₂S)
3. AsO₃^3-(conjugate base of the weaker acid, H₃AsO₃)

500

A generic weak acid (formula = HA) has a pK_a of 4.0. If the solution pH is 3.0, what is the initial concentration of the acid?

0.01 M

Acids Bases 3

100

Name 6 of the 7 strong acids.

HCl, HBr, HI, HNO₃, HClO₃, HClO₄, first dissociation of H₂SO₄

200

List the following carboxylic acids in order of increasing strength: CHCl₂COOH, CCl₃COOH, CH₃COOH, CH₂ClCOOH.

CH₃COOH < CH₂ClCOOH < CHCl₂COOH < CCl₃COOH

300

What is the percentage deprotonation of acetic acid, CH₃COOH, when the [H₃O⁺]= 1.2 x 10^-3M. The initial concentration of the acid is 0.10 M.

1.2 %

400

Estimate the pH of 0.2 M NaH₂PO₄(aq). For phosphoric acid: pK_a1 = 2.0, pK_a2 = 7.0, pK_a3 = 12.5

pH=(pK_a1+pK_a2)/2=(2.0+7.0)/2=4.5

500

A generic weak base (formula = B) has a pK_b of 5.0 If the initial concentration of the base is 0.1 M, what is the solution pH?

11.0

Buffers/Titrations 1

100

What is a buffer solution? Give an example.

A buffer is a mixture of a weak conjugate acid-base pair that stabilizes the pH of the solution by providing both the source and the sink for protons.

1. acid buffer: CH₃COOH / CH₃COONa

2. basic buffer: NH₃/NH₄Cl

200

 What is the pH halfway to the stoichiometric point?

pH = pK_a

300

Predict whether the stoichiometric point of each of the following titrations is below, above, or at pH 7:

1. CH₃COOH titrated with NaOH
2. NH₃ titrated with HCl
3. KOH titrated with HBr

1. above pH 7
2. below pH 7
3. at pH 7

400

The analyte consisting of 25.0 mL of x M NH₃ (aq) was titrated using 50.0 mL of 0.25 M HCl. What is the concentration of the analyte?

0.50 M

500

What is the pH of a 0.1 M diprotic weak acid solution with K_a1= 1 x 10^-3 and K_a2 =1 x 10^-8 ?

2.0

Buffers/Titrations 2

100

What is an acid-base indicator? What is the endpoint of an indicator?

Acid-base indicator is a water-soluble organic dye with a color that depends on pH.

The endpoint of an indicator is the point at which the concentrations of its acid and base forms are equal.

200

Thymol blue has two color changes:

• red to yellow at ~pH 3
• yellow to blue at ~pH 9

Which color change will generally be more suitable for titration of a weak acid with a strong base?

yellow to blue

300

What is the pH of a buffer solution made of 10.0 mL of 0.25 M HCOOH and 10.0 mL of 0.25 M NaCOOH. pK_a (HCOOH) = 3.75

3.75

400

The analyte consisting of 20.0 mL of x M Ca(OH)₂ (aq) was titrated using 20.0 mL of 0.20 M HCl. What is the concentration of [OH^-] ions?

0.20 M

500

What is the pH of a 0.1 M diprotic weak acid solution with K_a1= 1 x 10^-2 and K_a2 = 1 x 10^-6 at the first stoichiometric point?

pH= (pK_a1 + pK_a2/2 = (2.0 + 6.0)/2 = 4.0