the ph of a stpong acid solution - voorhees...

Acids and Bases Packet

Name:________________________

Mods:________________________

Values of Ka for Some Common Monoprotic Acids

Name Formula Value of Ka

Hydrogen sulfate ion Chlorous acid Monochloracetic acid Hydrofluoric acid Nitrous acid Formic acid Lactic acid Benzoic acid Acetic acid Hydrated aluminum(III) ion Propanoic acid Hypochlorous acid Hypobromous acid Hvdrocyanic aid Boric acid Ammonium ion Phenol Hypoiodous acid

HSO4-

HClO2 HC2H3ClO2 HF HNO2 HCO2H HC3H5O3 HC7H502 HC2H3O2 [Al (H20)6]3+

HC3H5O2 HOCl HOBr HCN H3BO3 NH4

+

HOC6H5

HOI

1.2 x 10-2 1.2 x 10-2 1.35 x 10 -3

7.2 x 10-4

4.0 x 10-4 1.8 x 10-4 1.38 x 10-4 6.4 x 10-5 1.8 x 10-5 1.4 x 10-5 1.3 x 10-5 3.5 x 10-8 2 x 10-9

6.2 x 10-10 5.8 x 10-10 5.6 x 10-10 1.6 x 10-10 2 x 10-11

Stepwise dissociation constants for several common polyprotic acids

Name Formula Ka1 Ka2 Ka3

Phosphoric acid Arsenic acid Carbonic acid Sulfuric acid Sulfurous acid Hydrosulfuric acid Oxalic acid Ascorbic acid (Vitamin C) Citric acid

H3P04 H3AsO4 H2CO3 H2S04 H2S03 H2S H2C204 H2C6H6O6 H3C6H5O7

7.5 x 10-3 5 x 10-3 4.3 x 10-7 Large 1.5 x 10-2 1.0 x 10-7 6.5 x 10-2 7.9 x 10-5

8.4 x 10-4

6.2 x 10-8 8 x 10-8 5.6 x 10-11 1.2 x 10-2

1.0 x 10-7 ~10-19

6.1 x 10-5 1.6 x 10-12 1.8 x l0

4.8 x 10-13

6 x 10-10

4.0 x 10-6

Values of Kb for some common weak basesName Formula Conjugate acid Kb

Ammonia Methylamine Ethylamine Diethylamine Triethylamine Hydroxylamine Hydrazine Aniline Pyridine

NH3 CH3NH2 C2H5NH2 (C2H5)2NH (C2H5)N HONH2 H2NNH2 C6H5NH2 C5H5N

NH4+

CH3NH3+

C2H5NH3+

(C2H5)2NH2+

(C2H5)NH+ HONH3

+ H2NNH3

+ C6H5NH3

+ C5H5NH+

1.8 x 10-5 4.38 x 10-4 5.6 x 10-4 1.3 x 10-3 4.0 x 10-4

1.1 x 10-8

3.0 x 10-6 3.8 x 10-10

1.7 x 10-9

WORKSHEET 1Write ACID, BASE or BOTH on the line.

_______1. Litmus turns blue in this.

_______2. Phenolphthalein turns clear in this.

_______3. Produces hydroxide.

_______4. Is often slippery or slimy.

_______5. Produces hydrogen.

_______6. Does not react with metals.

_______7. Phenolphthalein turns pink in this.

_______8. Stings in cuts.

_______9. Litmus turns red in this.

_______10. Often tastes sour.

_______11.Reacts with metals.

_______12. Looks like water

_______13. Bromothymol Blue turns blue in this

_______14. Bromothymol Blue turns yellow in this

Identify the following as an ACID, BASE, CARBONATE, METAL or SALT.

A. LiOH _________________________________________

B. HCl _________________________________________

C. Na2CO3 _________________________________________

D. Mg _________________________________________

E. HBr _________________________________________

F. KCl _________________________________________

WORKSHEET 2Write the name or formula for the following:

1. hydroiodic acid ______________________________

2. iodic acid ______________________________

3. sulfurous acid ______________________________

4. nitric acid ______________________________

5. acetic acid ______________________________

6. magnesium hydroxide ______________________________

7. calcium hydroxide ______________________________

8. lithium hydroxide ______________________________

9. HCl ______________________________

10. H2SO4 ______________________________

11. HClO2 ______________________________

12. HNO2 ______________________________

13. H3PO4 ______________________________

14. KOH ______________________________

15. Al(OH)3 ______________________________

16. hydrobromic acid ______________________________

17. sulfuric acid ______________________________

18. strontium hydroxide ______________________________

19. sodium hydroxide ______________________________

20. HI _____________________________

21. H2SO3 ______________________________

22. HClO4 ______________________________

23. LiOH ______________________________

WORKSHEET 3Reactions with acids and metals

Metal + acid à ________ + _________

1. ____HCl + _____K à ______ + ______

2. ____HI + ___Li à _____ + ______

3. ___HBr + ____Ba à ______ + ______

Reactions with acids and carbonates

Acid + carbonate à __________ + __________ + _________

1. _____ HF + _____ Ca(CO3) à _______ + _________ + __________

2. _____ HCl + _____ Li2 (CO3) à _______ + ________ + __________

3. _____ HI + _____ Mg(CO3) à _______ + _________ + _________

Reactions with acids and bases

Acid + base à ____________ + _____________

1. _____ NaOH + HCl à _______ + ________

2. _____Al(OH)3 + HF à _______ + ________

3. _____ Ca(OH)2 + HNO3 à ______ + ________

WORKSHEET 4Complete and balance the following after predicting products

1. Calcium and hydrobromic acid à

2. Iron II carbonate and chloric acid à

3. Barium hydroxide and nitrous acid à

4. Lithium hydroxide and phosphoric acid à

5. Aluminum and sulfuric acid à

6. Chromium III carbonate and acetic acid à

WORKSHEET 5

1. Draw and Label a pH scale

2. Calculate the pH of solutions with the following [H3O+]. Identify the solution asacidic, basic or neutral.

a) 1.00 x 10-3

b) 1.00 x 10-10

c) 6.59 x 10-10

d) 9.47 x 10-3

3. Find the pH of each of the following solutions and identify them as acidic, basic orneutral

a) pOH = 2.00

b) pOH = 8.00

c) pOH = 1.263

d) pOH = 9.714

4. Calculate the pH of solutions with the following [OH-]. Identify the solution asacidic, basic or neutral.

a) 1.00 x 10-9

b) 1.00 x 10-3

c) 9.56 x 10-4

d) 7.49 x 10-10

5. Find the pH and the [H3O+] of each of the following solutions and identify them as acidic, basic or neutral

a) pOH = 9.50

b) pOH = 3.65

c) pOH = 12.63

d) pOH = 1.14

6. Fill in the following chartSubstance [H3O+] [OH-] pH pOH

HCl 2.50 x 10-2

H2SO4 5.62 x 104

NaOH 9.82

NH4OH 3.64

WORKSHEET 6 (NOTES)The pH of a STRONG acid solution

PROBLEM: Calculate the pH and the pOH of a 5x10-3 M HClO4 solution.

STEP 1: List the major species in the solution.

STEP 2: Choose the species that can produce H+ and write balanced equations for the reactions producing H+.

STEP 3: Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium will dominate in producing H+

STEP 4: Write the equilibrium expression for the dominant equilibrium.

STEP 5: List the initial concentrations of the species participating in the dominant equilibrium.

STEP 6: Since we have already determined that this is a strong acid, it will completely dissociate. Write the change needed to achieve equilibrium.

STEP 7: Calculate the pH using the strong acid concentration. Use this to find pOH.

WORKSHEET 7The pH of a STRONG acid solution (PRACTICE)

PROBLEM: A solution is prepared by adding 15.8 g of HCl to enough water to make a total volume of 400 mL. What is the pH of the solution? How much hydrogen ion is contributed by the autoprotolysis of water?

STEP 1: List the major species in the solution.

STEP 2: Choose the species that can produce H+ and write balanced equations for the reactions producing H+.

STEP 3: Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium will dominate in producing H+

STEP 4: Write the equilibrium expression for the dominant equilibrium.

STEP 5: List the initial concentrations of the species participating in the dominant equilibrium.

STEP 6: Since we have already determined that this is a strong acid, it will completely dissociate. Write the change needed to achieve equilibrium.

STEP 7: Calculate the pH using the strong acid concentration. Use this to find pOH.

WORKSHEET 8 (NOTES)The pH of a WEAK acid solutionCalculate the pH of a 0.500 M aqueous solution of formic acid, HCOOH [Ka=1.77 x 10-4]

Step 1 List the major species in the solution.

Step 2 Choose the species that can produce H+, and write balanced equations for the reactions producing H+.

Step 3 Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium will dominate in producing H+.

Step 4 Write the equilibrium expression for the dominant equilibrium.

Step 5 List the initial, change and final concentrations of the species participating in the dominant equilibrium. **ICE CHART**

Step 6 Substitute the equilibrium concentrations into the equilibrium expression.

Step 7 Solve for x the “easy” way- that is, by assuming that [HA]0 - x = [HA]

Step 8 Use the 5% rule to verify whether the approximation is valid.

Step 9 Calculate [H+] and pH and whatever else the problem asks for

WORKSHEET 9The pH of a WEAK acid solution (PRACTICE)

The value for Ka = 7.45 x 10-4 for citric acid (C6H10C8) (We’ll call it HCA) Calculate the pH of a 0.200 M HCA solution.

Step 1

List the major species in the solution.








Step 9 Calculate [H+] and pH and whatever else the problem asks for

WORKSHEET 10 (PRACTICE)A solution is prepared by dissolving 12.2 g benzoic acid (C6H5CO2H, Ka = 6.4 10-5 ) in enough water to make 1.00 L of solution. Calculate [C6H5CO2H], [C6H5CO2

-], [H+], [OH-], and the pH of this solution.

Step 1 List the major species in the solution.

Step 2 Choose the species that can produce H+ , and write balanced equations for the reactions producing H+ .

Step 3 Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium will dominate in producing H+ .

Step 4 ‘Write the equilibrium expression for the dominant equilibrium.





Step 9 Calculate [H+] and pH and whatever else the problem is asking for.

WORKSHEET 11 (NOTES)pH of a mixture of weak acids Calculate the pH of a mixture of 2.00 M formic acid (HCOOH, Ka = 1.77x10-4) and 1.50 M hypobromus acid (HOBr, Ka 2.06 x 10-9). What is the concentration of both the hypobromite ion (OBr-) and the hydroxide (OH-) ion at equilibrium? Step 1 List the major species in the solution.



Step 9 Calculate [H+] and pH and whatever else

WORKSHEET 12 (PRACTICE)pH of a mixture of weak acids 2Calculate the pH of a solution that contains 1.0M HF (Ka = 7.2 x 10-4) and 1.0M HOC6H5

(Ka = 1 .6 x 10-10). Also calculate the concentration of 0C6H5- in the solution at

equilibrium. Step 1 List the major species in the solution.

Step 2 Choose the species that can produce H+, and write balanced equations for the reactions

producing H+.







Step 9 Calculate [H+] and pH and whatever else

WORKSHEET 13 Percent Dissociation (NOTES)Often we need to specify the amount of a weak acid that has dissociated when equilibrium has been achieved.

Percent dissociation = amount dissociated (M) X 100% initial conc (M)

If we know that a 1.00 M solution of HF has an [H+] 2.7 x 10 -2 M. What is the percent dissociation?

Percent dissociation = _______________ X 100%

Percent Dissociation WORKSHEET 14For a weak acid, the percent dissociation increases as the acid becomes more dilute.

Calculate the percent dissociation of acetic acid (Ka = 1.8 x 10-5) in each of the following

solutions. A. 1.00 M HC2H302 (NOTES)B. 0.100 M HC2H302 (PRACTICE)

Solve for the [H+) concentration of both solutions like we did earlier for a weak acid.

The results show 2 important facts: 1. The concentration of the H+ ion is less for .10 M acetic acid than the 1.0 M acetic acid.

2. The percent dissociation for the .10 M solution is greater than the 1.0 M.

WORKSHEET 15 (NOTES)Lactic acid (HC3H503) is a waste product that accumulates in muscle tissue during exertion, leading to pain and a feeling of fatigue. In a 0.100 M aqueous solution, lactic acid is 3.7% dissociated. Calculate the value of K for this acid.

WORKSHEET 16 (PRACTICE)

In a 0.500 M solution, uric acid (HC5H3N4O4) is 1.6% dissociated.. Calculate the value of Ka

for uric acid.

Bases Arrhenius concept- base is a substance that produces 0H- ions in aqueous solution Bronsted-Lowry- base is a proton acceptor

Bases like sodium hydroxide (NaOH) and potassium hydroxide (KOH) fulfill both criteria—they dissociate completely. Strong bases- dissociate completely All hydroxides of Group 1 (alkali elements) are strong bases Group 2 hydroxides (alkaline earth elements) are strong bases- 2 moles of 0H-

produced for each mole of compound, they are not very soluble (good for antacids Al(OH)3 and Mg(OH)2—don’t dissolve in mouth, esophagus, and stomach... but dissolve with excess stomach acid to cure indigestion)

Bases – WORKSHEET 17 (NOTES)pH of a STRONG base Calculate the pH of a solution made by putting 4.63 g of LiOH into water and diluting to a total volume of 400 mL. Step 1- List the major species in solution

Step 2- Write the reactions that can produce 0H- ions

Step 3- Choose which reaction will dominate 0H- production

Step 4- If it is a strong base, the 0H- will be equal to the molarity of the base.

Step 5- The concentration of H+ can be calculated from Kw .

Step 6- Calculate the pH using the H+ concentration.

WORKSHEET 18 (NOTES)

Many types of proton acceptors (bases) do not contain the hydroxide ion, but when they are dissolved in water, they increase the concentration of the hydroxide ion because of their reaction with water. Example: NH3 acts as a base because it is a proton acceptor NH3(aq) + H2O(l) à NH4

+ (aq) + 0H- (aq)

Label the acid, base, conjugate acid and conjugate base in the above reaction.

Bases such as ammonia often have an unshared pair of electrons that is capable of forming a bond with a proton. Most of these bases have N with a lone pair. Some examples are: (CH3)NH2, (CH3)2NH, (CH3)3N, C2H5NH2, C5H5N

The general reaction between a base B and water is given by: B(aq) + H20(l) àBH+ (aq) + 0H- (aq)

Label the conjugate pairs and write the Kb expression.

Kb = _______________

Kb always refers to the reaction of a base with water to form the conjugate acid and the hydroxide ion.

Bases – WORKSHEET 19 (NOTES)Calculate the pH of a 0.350 M solution of methylamine, CH3NH2 (Kb = 4.38 x 10-4)

Step 1-List the major species in the solution

Step 2- Choose the species that can produce 0H- , and write balanced equations for the reactions producing 0H- .

Step 3- Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium is producing 0H- .

Step 4- Write the equilibrium expression for the dominant reaction.

Step 5, 6, 7- List the initial concentrations of the species participating in the dominant equilibrium. Then, define the change needed to achieve equilibrium—that is, define x. Write the equilibrium concentrations in terms of x. **ICE CHART**

Step 8- Substitute the equilibrium concentrations into the equilibrium expression.

Step 9- Solve for x the “easy” way, that is, by assuming that [HA]0 – x = [HA]0

Step 10- Use the 5% rule to verify whether the approximation is valid.

Step 11- Calculate [OH-], pOH, [H+], and pH. We can calculate [H+] from Kw and then calculate the pH or we can find the pOH from the [0H-] and then use pKw = 14.00 = pH + pOH

Bases – WORKSHEET 20 (PRACTICE)Calculate the pH of 1.0 M solution of methylamine (CH3NH2) (Kb = 4.38 x 10-4) Step 1-List the major species in the solution

Step 2- Choose the species that can produce 0H- , and write balanced equations for the reactions producing 0H- .

Step 3- Using the values of the equilibrium constants for the reactions you have written, decide which equilibrium is producing 0H- .

Step 4- Write the equilibrium expression for the dominant reaction.

Step 5, 6, 7- List the initial concentrations of the species participating in the dominant equilibrium. Then, define the change needed to achieve equilibrium—that is, define x. Write the equilibrium concentrations in terms of x. **ICE CHART**

Step 8- Substitute the equilibrium concentrations into the equilibrium expression.

Step 9- Solve for x the “easy” way, that is, by assuming that [HA]0 – x = [HA]0

Step 10- Use the 5% rule to verify whether the approximation is valid.

Step 11- Calculate [OH-], pOH, [H+], and pH. We can calculate [H+] from Kw and then calculate the pH or we can find the pOH from the [0H-] and then use pKw = 14.00 = pH + pOH

WORKSHEET 21 (NOTES)

Common Ion Effect Consider the following reaction: HF(aq) ó H+

(aq) + F-(aq)

Initially in solution, what will take place when we add the HF?

What would happen if we were to add F- or H+ to the reaction? Which way would the equilibrium shift?

This shift is called the common ion effect. We are adding more of one of the ions already in solution. This makes this solution less acidic by inhibiting the HF from dissociating. This will alter our pH, however, our favorite steps for solving these types of problems are still the same! YEA!! Here’s a problem—try it! WORKSHEET 22 (PRACTICE)Calculate the pH, and the percent dissociation of the acid, in each of the following solution. 0.200 M HC2H3O2 (Ka= 1.8 x 10-5)

STEP 1: List the major species

STEP 2: Choose the species that can dominate the reaction by comparing K values

STEP 3: Find the initial concentrations of all species involved.

STEP 4: List the initial, change and final concentrations in terms of x. ICE

STEP 5: Check the 5% rule

STEP 6: Find the pH. [H+] and % dissociation of the acid.

WORKSHEET 23 (NOTES)Find the pH and the percent dissociation of the acid, in the following solution. 0.200 M HC2H3O2 in the presence of 0.500 M NaC2H3O2. STEP 1: List the major species

STEP 2: Choose the species that can dominate the reaction by comparing values



STEP 5: Check the 5% rule

STEP 6: Find the pH, [H’] and % dissociation of CH3COOH.

Buffered Solutions

These are one of the most important acid-base solutions. The most common and maybe most important example is blood. A buffered solution, such as blood, has the ability to resist a change pH. All a buffered solution is a weak acid and its salt (HF and NaF) or a weak base and its salt (NH3 and NH4Cl). Try it! WORKSHEET 24 (NOTES)Calculate the pH of a solution that contains 0.250 M formic acid, HCOOH(Ka 1.8x10-4) and 0.100 M sodium formate NaCOOH.

STEP 1: List the major species - include whatever acid/base properties the species have




STEP 5: Check the 5 % rule

STEP 6: Find the pH, [H+] and % dissociation

Basic Buffers (a fancy name for common ion effect)

To buffer a solution at a basic pH requires a weak base and its salt. For example, one might use NH3 (Kb 1.8 x 10-5) acid NH4Cl.

WORKSHEET 25 (PRACTICE)Consider a solution containing 0.30 M NH3 and 0.20 M NH4Cl.

STEP 1: List the major species - include whatever acid/base properties the species have




STEP 5: Check the 5 % rule

STEP 6: Find the pH, [H+] and % dissociation

REVIEW PROBLEMS ACIDS WORKSHEET 26 (PRACTICE)

1. Using the Ka values, calculate the percent dissociation in a 0.20 M solution of each of the following acids.

a. nitric acid (HNO3)b. nitrous acid (HNO2) Ka = 4.1 x 10-4

c. phenol (HOC6H5) Ka = 1.6 x 10-10 d. How is the percent dissociation related to the Ka value for the acid?

2. Calculate the pH of a solution that contains 1.5 M HF and 2.0 M HOC6H5. Also calculate the concentration of OC6H5

- in this solution at equilibrium.

Ka for HF is 7.2 x 10-4

Ka for HOC6H5 is 1.6 x 10-10

3. Calculate [OH-], [H+], and the pH of a 0.20 M solutions of each of the following amines.

a. Triethylamine [(C2H5)3N, Kb = 4.0 x 10-4]b. Hydroxylamine (HONH2, Kb = 1.1 x 10-8]

4. Sodium azide (NaN3) is sometimes added to water to kill bacteria. Calculate the concentration of all species in a 0.010 M solution of NaN3. The Ka value for hydrozoic acid (HN3) is 1.9 x 10-5.

WORKSHEET 27 Buffer Homework and Test Review (PRACTICE)

1. Calculate the pH of each of the following solutions.

a. 0.100 M propanoic acid (HC3H5O2 Ka = 1.3 x 10-5)

b. A mixture containing 0.100 M HC3H5O2 and 0.100 M NaC3H5O2

c. Compare the percent dissociation of the acid in a with the acid in d. Explain the large difference in the percent dissociation of the acid.

2. Calculate the pH of a solution which is 1.00 M HF and 1.00 M KF. Ka for HF = 7.2 x 10-4

3. Calculate the pH of a solution which is 0.50 M CH3NH2 and 0.70 M CH3NH3Cl.

Kb for CH3NH2 = 4.38 x 10-4

4. Calculate the pH of each of the following buffered solutions.

HC2H3O2 Ka = 1.8 x 10-5

C2H5NH2 Kb = 5.6 x 10-4

a. 0.10 M acetic acid/0.25 M sodium acetateb. 0.25 M acetic acid/0.10 M sodium acetatec. 0.50 M C2H5NH2/0.25 M C2H5NH3Cld. 0.25 M C2H5NH2/0.50 M C2H5NH3Cl

Part 2: Identify the conjugate acid/base pairs

5. . NH3 + H3O+ à NH4+ + H2O

6. . CH3OH + NH2- à CH3O - + NH3

7. . OH- + H3O+ à H2O + H2O

8. . NH2- + H2O à NH3 + OH-

Part 3: fill in the following chart

Substance [H3O+] [OH-] pH pOH

HCl 2.50 x 10-2

H2SO4 5.62 x 10 -4

NaOH 9.82

NH4OH 3.64

9. . What is the pH scale - label

10. What color does litmus paper turn in an acid?

11. What color does bromothymol blue turn in a base?

12. What color does phenolphthalein turn in an acid?

Part 4: Complete and balance the following after predicting products

13. Calcium and hydroiodic acid à

14. Copper II carbonate and perchloric acid à

15. Magnesium hydroxide and nitrous acid à

Part 5: Solve for the molarity of the acid from the following data:

MB = .35 M MA = ?

VB = 15.4 mL VA = 16.3 mL

MAVA = MB VB solve for MA

Part 6: Problems (Show all work!!)

16. Find the Ka of a 0.120M HBr solution if it has a [H3O+] of 4.20 x 10-5

17. Determine the [H2CO3] if the [H3O+] is 4.20 x 10-6M

18. Find the [H3O+] of H3PO4 in a 0.800 M solution (Ka=7.08 x 10-3)

19. What is the [H3O+] of 0.100 M HCOOH? What is the percent ionization?

(Ka = 1.77 x 10-4)

20. A solution has HCN concentration of 1.30 x 10-3 and a KCN concentration of 0.820M. Calculate the hydrogen ion concentration. (Ka = 6.17 x 10-10)

21. What is the [H3O+] in a solution of 0.150M HNO2. Calculate the pH of the solution and percent ionization. (Ka = 7.24 x 10-4)

22. If 0.030M NaNO2 is added to the solution in question #21, what is the [H3O+], pH and percent ionization?

the ph of a stpong acid solution - voorhees...

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