Highlander Help

CHAPTER 15 REGULAR HOMEWORK:

INTRO. ACIDS

Resources:

Have you found videos, websites, or explanations that helped you understand this chapter? Let us know and we'll add them to "Resources" part of this page for other students to use.


 

Question 1

\What is the pH of a solution where the [H+] =6.91 x 10-3 M?

REPORT pH TO 2 DECIMAL PLACES.


Correct

 

Explanation

 pH=-log(6.91e-3)

pH=2.16

 

Question 2

Is the above pH acidic or basic?


Select one:

Correct

 

 

 

Question 3

What is the [H+] concentration if the pH is 7.19?

Correct

 

Explanation

 

 [H+]=10^-7.19

[H+]= 1e^-19

 

Question 4

Is the above pH acidic or basic?


Select one:


Correct

 

 

 

Question 5

What is the [H+] concentration if the pOH is 8.19?

Correct

 

Explanation

pOH + pH =14

14-8.19= pH

pH= 5.81

10^-5.81= [H+]

1.549e-6=[H+]

 

Question 6

Is the above pH acidic or basic?


Select one:

Correct

 

    

 

Question 7

What is the [H+] concentration if the [OH-] concentration is 9.90 x 10-11 M?


Correct

 

Explanation

 [OH-][H+]=1e-14

[H+]= (1e-14)/(9.9e-11)

[H+]=1.01e-4

 

Question 8

Is the above [H+] concentration acidic or basic?


Select one:

Correct

 

 

 

Question 9

Calculate the pH of 0.095 M HClO4.

Correct

 

Explanation

 pH=-log[0.095]

pH=1.022

 

Question 10

Calculate the pH of 0.618 M HNO3.

Correct

 

Explanation

 pH=-log(0.618)

pH=0.209

 

Question 11

Calculate the pH of 0.0084 M NaOH.

Correct

 

Explanation

 pH=-log(0.0084)

pH=2.076

14-2.076=pH

pH=11.92

 

Question 12

Calculate the pH of 0.0019 M Ba(OH)2. Careful.

Correct

 

Explanation

 pOH=-log(0.0019*2)

pH=2.42

14-2.42=pH

pH=11.58

 

Question 13

Calculate the pOH of 0.020 M LiOH.

Correct

 

Explanation

 pOH=-log(0.02)

pOH=1.69897

 

Question 14

Calculate the pOH of 0.17 M HI.

Correct

 

Explanation

 pH=-log(0.17)

pH=0.7696

14-pH=pOH

pOH=13.23

 

Question 15

Calculate the pOH of 0.00039 M Sr(OH)2.

Correct

 

Explanation

 pOH=-log(0.00039*2)

pOH=3.108

 

Question 16

When 1.00 g of thiamine hydrochloride (also called vitamin B1 hydrochloride) is dissolved in water, then diluted to 10.00 mL, the pH of the resulting solution is 4.50. The formula weight of thiamine hydrochloride is 337.3 g/mol. Calculate Ka.

Correct

 

Explanation

 1 g * 1 mol/ 337.3 g = 0.00296472

0.00296/0.01 L = 0.296 M

pH= 4.50 = -log[H+]

[H+]=0.00003

Ka = [H+][A-]/[HA]

Ka= 0.00003^2/0.296

 

Question 17

When 0.0021 moles of a weak acid are dissolved in enough water to make 0.500 L, the pH of the resulting solution is 6.04. Calculate Ka.

Correct

 

Explanation

 0.0021/0.5L = 0.0042M [HA]

pH=6.04= -log[H+]

[H+]=9.12e-7

Ka=[H+][A-]/[HA]

Ka= (9.12e-7)^2/(0.0042)

 

Question 18

Rank the following acids from least acidic (highest pH) to most acidic (lowest pH). Scheme: Least acidic 5 to most acidic 1.

Fig
acetic acid Correct
chlorous acid Correct
hydrocyanic acid Correct
hydrosulfuric acid Correct
phenol Correct

 

 

 

Question 19

Rank the following acids in order of increasing acid strength. Key: bond strength
HF Correct
HCl Correct
HBr Correct
HI Correct

 

 

Hint, for similar compounds, does bond strength decrease or increase with increasing size (going down a column)?

 

Question 20

Rank the following acids in order of increasing acid strength. Key: Weakening of hydrogen bond and stability of resulting anion. (Electronegativities I="2.5," Br="2.8," Cl="3," and F="4.)

HOF (if it existed) Correct

HOCl Correct

HOBr Correct

HOI Correct

 

 

 

Question 21

Rank the following acids in order of increasing acid strength. Key: Stability of anion.
HOCl Correct
HOClO Correct
HOClO2 Correct
HOClO3 Correct

 

 
Spreading out the electron density in the anion increases its stability.

 

Question 22

In the following acid-base reaction, identify the compounds as acid, base, conjugate acid, and conjugate base. 

NH3 + H2O ↔ NH4+ +OH-
NH3 Correct
H2O Correct
NH4+ Correct
OH- Correct

 

 

 

Question 23

For the above reaction indicate the type


Select one:


Correct

 

 

 

Question 24

In the following acid-base reaction, identify the compounds as acid, base, conjugate acid, and conjugate base. 

HSO4- + H2O ↔ SO42- +H3O+
HSO4- Correct
H2O Correct
SO42- Correct
H3O+ Correct

 

 

 

Question 25

For the above reaction indicate the type


Select one:


Correct

 

 

 

Question 26

In the following Lewis acid-base reaction for liquid ammonia, identify the compounds as acid, base, conjugate acid, and conjugate base.

NH3 + NH3 ↔ NH4+ +NH2-

NH3 Correct

NH4+ Correct

NH2- Correct

 

 Note, this is like the autoionization of water.

 

Question 27

For the above reaction indicate the type


Select one:


Correct

 

 

 

Question 28

Which of the following is/are correct for the NH2- ion?


Select one or more:


  Correct
Correct

 

 An extremely weak acid is normally not considered an acid. Similar an extremely weak base is normally not considered a base.

 

Question 29

In the following Lewis acid-base reaction, identify the compounds as acid, base, conjugate acid, and conjugate base.

Zn(OH)3-(aq) + OH-(aq) ↔ Zn(OH)42-(aq)

Zn(OH)3-(aq) Correct

OH- Correct

Zn(OH)42- Correct

 

 

 

Question 30

For the above reaction indicate the type


Select one:


 
  Correct

 

 

 

Question 31

Rank the following species in order of increasing basicity. NH3, NH4+,+NH2-, Cl-,H2O

NH3Correct

NH4+Correct

NH2-Correct

Cl-Correct

H2OCorrect





 

 

 

Question 32

Which of the following is/are correct for the F- ion?


Select one or more:


Correct

Correct


 

 

 

Question 33

Which of the following is/are correct for the Br- ion?


Select one or more:

 

Correct


Correct

 

 

 

Question 34

Which of the following is/are correct for the Ca2+ ion?


Select one or more:



Correct



Correct

 

 

 

Question 35

Which of the following is/are correct for the Fe3+ ion?


Select one or more:



Correct

 

 

 

Question 36

Which of the following is/are correct for CH3NH2?


Select one or more:


Correct

Correct

 

 

 

Question 37

Which of the following is/are correct for the H2PO4- ion?


Select one or more:

Correct


Correct

 

 

 

 

Question 38

Phenol (C6H5OH, also called carbolic acid) has a pKa of 9.89. It is used to preserve body tissues and is quite toxic. Calculate the percent ionized in 0.0868 M phenol--a dilute solution.

Correct

 

Explanation

 pKa= -log(Ka)

Ka= 10^-9.89=1.288e^-10

1.288e-10=[H+][A-]/[HA]=x^2/0.0868

x=3.344e^-6

%ionized = 0.34e-6/0.0868 * 100 = 0.00385%

 

Question 39

Calculate the percent ionized in 9.33x10-6 M phenol--a very dilute solution.

Correct

 

Explanation

 Ka= 1.288e^-10=x^2/9.33e^-6

x=3.5e^-8

3.5e^-8/(9.33e^6-6) * 100 = 0.372%

 

Question 40

Based on the last two problems, as a weak acid is diluted the percent ionized


Select one:

Correct

 

 

 

Question 41

A solution is made by dissolving 31.4 g of NaOH in approximately 450 mL of water in a volumetric flask. The solution becomes quite warm, but after it is allowed to return to room temperature, water is added to total 500 mL of solution. Calculate the pH of the final solution. Report pH to 2 decimal places.

Correct

 

Explanation

 3.14g * 1 mol/ 39.997 g = 0.785 mol/0.5L = 1.57M [NaOH]

pOH= -log[OH-]

=-log(1.57)

=-0.1959


pOH + pH = 14

14 + 0.1959 = 14.1959

 

Question 42

Why wait for the solution to return to room temperature before adding the rest of the water? (More than one answer is required.)


Select one or more:




  Correct
Correct

 

 

 

Question 43

sodium hydroxide solution at an elevated temperature of 50ºC.

(Recall, Kw is for water's autodissociation, that is, H2O ↔ H+ + OH-. Remember normally pH is measured at 25ºC. (Hint, this reaction is the reverse of adding a base to an acid. In other words is it endothermic or exothermic?)


Select one or more:


Correct



Correct

 

Explanation

 LeChatelier's principle is useful in answering this question.