Name: ____________________________________________ Date: ______________ Period: ________ pH Worksheet

1. What is pH a measure of?

2. What is the equation used for finding pH

3. What is the equation that relates to pH and pOH?

4. Complete the following table

[H3O+] [OH

-] pH pOH Acidic/Basic?

1.0 x 10-9

M 1 x 10-5

5

2.4 x 10-13

M 12.6 1.4

5.62 x 10-11

M 3.75 10.25

2.82 x 10-9

M 3.55 x 10-6

M 8.55

5. What would be the pH of each of the following:

a) 0.0010 M HCl ____ g) 0.024 M HCl ____

b) 0.0010 M HNO3 ___ h) 0.075 M KOH ____

c) 0.010 M NaOH ____ i) 0.000034 M HCl ____

d) 0.0035 M HCl ____ j) 0.000000000001M HCl ____

e) 1.0 M HBr ____

f) 1.0 M KOH ____

6. A 2.63 g NaOH are dissolved in 156 mL of solution. Determine the NaOH concentration & the pH.

7. List 3 strong acids and explain why these acids are considered strong acids.

8. List 3 weak acids and explain why these acids are considered weak acids.

9. List 2 strong bases and explain why these bases are considered strong bases.

10. List 1 weak base and explain why it is considered a weak base.

Name: ____________________________________________ Date: ______________ Period: ________ pH Worksheet

KEY

1. What is pH a measure of? The concentration of H+ in solution

2. What is the equation used for finding pH? pH =-log [H+]

3. What is the equation that relates to pH and pOH? pH + pOH =14

4. Complete the following table

[H3O+] [OH

-] pH pOH Acidic/Basic?

1.0 x 10-9

M 1 x 10-5

9 5 Basic

2.4 x 10-13

M 4.1x10-2

M 12.6 1.4 Basic

1.78 x 10-4

M 5.62 x 10-11

M 3.75 10.25 Acidic

2.82 x 10-9

M 3.55 x 10-6

M 8.55 5.45 Basic

5. What would be the pH of each of the following:

a) 0.0010 M HCl __3__ g) 0.024 M HCl _1.6___

b) 0.0010 M HNO3 __3_ h) 0.075 M KOH __12.9__

c) 0.010 M NaOH __12__ i) 0.000034 M HCl _4.5___

d) 0.0035 M HCl __2.46__ j) 0.000000000001M HCl __12__

e) 1.0 M HBr ___0_

f) 1.0 M KOH __14__

6. A 2.63 g NaOH are dissolved in 156 mL of solution. Determine the NaOH concentration & the pH.

2.63 g NaOH x 1 mol NaOH =0.0658 mol NaOH 156 mL x 1 L =

40.0 g NaOH 1000 ML

[NaOH]= 0.0658 mol NaOH/0.156 L = 0.42 M

pH =-log [0.42 M] = 0.37

7. List 3 strong acids and explain why these acids are considered strong acids.

HClO4, H2SO4, HNO3 They are strong since they dissociate 100% in water giving the maximum amount

of H+ ion from the compound

8. List 3 weak acids and explain why these acids are considered weak acids.

HC2H3O2, H3PO4, HNO2 They are weak since they dissociate much less than 100% in water so there is a

large portion of the original acid present

9. List 2 strong bases and explain why these bases are considered strong bases.

NaOH, Ba(OH)2 They are strong since they dissociate 100% in water giving the maximum amount

of OH- ion from the compound . The water formed is a very stable compound

10. List 1 weak base and explain why it is considered a weak base.

NH3 This compound does not hold onto the proton very strongly since it is less stable when it does accept

the proton (NH4+)

© 2004 Cavalcade Publishing, All Rights Reserved For chemistry help, visit www.chemfiesta.com

pH Calculations

1) Determine the pH of the following solutions:

a) A 4.5 x 10-3 M HBr solution.

b) A 3.67 x 10-5 M KOH solution.

c) A solution made by diluting 25 mL of 6.0 M HCl until the final

volume of the solution is 1.75 L.

d) 5 L of an aqueous solution that contains 1.0 grams of HBr and 1.0

grams of nitric acid.

2) What are the pOHs for the solutions in problem 1?

a) ___________________________ b) ___________________________ c) ___________________________ d) ___________________________

© 2004 Cavalcade Publishing, All Rights Reserved For chemistry help, visit www.chemfiesta.com

3) Explain why even a basic solution contains some H+ ions. 4) Explain why even an acidic solution contains some OH- ions. 5) More challenging: What is the pH of a 1.5 x 10-10 HBr solution? 6) Does your answer from problem #5 make sense? Explain.

© 2004 Cavalcade Publishing, All Rights Reserved For chemistry help, visit www.chemfiesta.com

pH Calculations – Answers

1) Determine the pH of the following solutions:

a) A 4.5 x 10-3 M HBr solution. 2.4 b) A 3.67 x 10-5 M KOH solution. 9.56 c) A solution made by diluting 25 mL of 6.0 M HCl until the final

volume of the solution is 1.75 L. 1.1 (the diluted solution is 0.086 M HCl) d) 5 L of an aqueous solution that contains 1.0 grams of HBr and 1.0

grams of nitric acid. 2.2 (the solution has an overall acid concentration of 0.0056 M) 2) What are the pOHs for the solutions in problem 1? a) 11.6 b) 4.44 c) 12.9 d) 11.8 3) Explain why even a basic solution contains some H+ ions. All aqueous solutions contain H+ ions from the autoionization of

water, H2O ���� H+ + OH-. 4) Explain why even an acidic solution contains some OH- ions. The same answer from #3 applies here. 5) More challenging: What is the pH of a 1.5 x 10-10 HBr solution? If you do the calculation to find –log (1.5 x 10-10), you get an answer

of 9.8. However, this is intuitively incorrect – after all, how can a solution that’s made of nothing but pure water (pH = 7) with an acid added be basic overall? The answer, it can’t. The actual pH of the solution is just about 7, with the main acid source being the H+ formed from the autoionization of water.

6) Does your answer from problem #5 make sense? Explain. See answer from #5.

pH Practice Worksheet 1) What is the pH of a solution that contains 25 grams of hydrochloric acid

(HCl) dissolved in 1.5 liters of water? 2) What is the pH of a solution that contains 1.32 grams of nitric acid (HNO3)

dissolved in 750 mL of water? 3) What is the pH of a solution that contains 1.2 moles of nitric acid (HNO3)

and 1.7 moles of hydrochloric acid (HCl) dissolved in 1000 liters of water? 4) If a solution has a [H+] concentration of 4.5 x 10-7 M, is this an acidic or

basic solution? Explain. 5) An acidic solution has a pH of 4. If I dilute 10 mL of this solution to a final

volume of 1000 mL, what is the pH of the resulting solution?

Solutions for the pH practice worksheet: The important thing to remember for all of these problems is that pH = -log [H+], and that [H+] is equivalent to the molarity of acid present in a solution. When the pH is less than 7, the solution is acidic, when the pH = 7 it is neutral, and when it is greater than 7, it is basic. 1) In this problem, there are 0.685 moles of HCl dissolved in 1.5 L H2O,

making a total acid concentration of 0.457 M. To find the answer, take the negative log of this to find that the pH = 0.34

2) pH = 1.55 3) pH = 2.53 4) The pH of this solution is 6.35, making the solution very slightly acidic. 5) The pH will be 6. This is solved in the same way that dilution problems

are solved. If the pH = 4, this means that the concentration of [H+] present is 0.0001 M. When you use the dilution equation, M1V1 = M2V2, where V2 is 1000 mL, you find that the concentration of acid after dilution is 1.00 x 10-6, which corresponds to a final pH of 6.

Acids and Bases

pH and pOH Calculations

1) Determine the pH of a 0.0034 M HNO3 solution. 2) Determine the pOH of a 0.0034 M HNO3 solution. 3) Determine the pH of a 4.3 x 10-4 M NaOH solution. 4) If a solution is created by adding water to 2.3 x 10-4 moles of NaOH and

4.5 x 10-6 moles of HBr until the final volume is 1 L, what is the pH of this solution?

5) Determine the pH of a 4.5 x 10-11 M NaOH solution. 6) Why would we say that a solution with a H+ concentration of 1.00 x 10-7 M

is said to be neutral. If it contains acid, shouldn’t it be acidic?

Acids and Bases

pH and pOH Calculations - Answers

1) Determine the pH of a 0.0034 M HNO3 solution.

pH = -log[H+] = -log(0.0034) = 2.47 2) Determine the pOH of a 0.0034 M HNO3 solution.

pH = -log[H+] = -log(0.0034) = 2.47 pOH = 14 – pH = 14 – 2.47 = 11.53

3) Determine the pH of a 4.3 x 10-4 M NaOH solution.

pOH = -log[OH-] = -log(4.3 x 10-4) = 3.37 pH = 14 – pOH = 14 – 3.37 = 10.63

4) If a solution is created by adding water to 2.3 x 10-4 moles of NaOH and

4.5 x 10-6 moles of HBr until the final volume is 1 L, what is the pH of this solution?

To solve:

• Both acid and base are present. Since they neutralize each other, you must first figure out how much acid or base is left over after it neutralizes. Since the amount of base is larger than the amount of acid, there will be more base than acid. The amount of base is 2.3 x 10-4 – 4.5 x 10-6 = 2.26 x 10-4 moles.

• Since there is one L of solution, the molarity of the base is 2.26 x 10-4 M.

• To find pOH, take the –log of 2.26 x 10-4, which is 3.65.

• To find pH, subtract 3.65 from 14. The pH of this solution is 10.35. 5) Determine the pH of a 4.5 x 10-11 M NaOH solution. Although there is some NaOH present in the solution, the pH isn’t

found by taking the –log of anything. The reason for this is that the concentration of base is much, much smaller than the concentration of acid which is naturally found in neutral water. As a result, this base doesn’t really have any affect on the pH, so the pH of the solution is 7.00.

6) Why would we say that a solution with a H+ concentration of 1.00 x 10-7 M is said to be neutral. If it contains acid, shouldn’t it be acidic?

It isn’t acidic because while there is some acid in the solution, there

is an equal quantity of base. In neutral solutions, the H+ and OH- concentrations are identical, because water breaks up to form them. As a result, the solution is neither acidic nor basic.