Concept explainers
Consider the following six beakers. All have 100 mL of aqueous 0.1 M solutions of the following compounds:
beaker A has HI
beaker B has HNO2
beaker C has NaOH
beaker D has Ba(OH)2
beaker E has NH4Cl
beaker F has C2H5NH2
Answer the questions below, using LT (for is less than), GT (for is greater than), EQ (for is equal to), or MI (for more Information required).
(a) The pH in beaker A the pH in beaker B.
(b) The pH in beaker C the pH in beaker D.
(c) The % ionization in beaker A the % ionization in beaker C.
(d) The pH in beaker B the pH in beaker E.
(e) The pH in beaker E the pH in beaker F.
(f) The pH in beaker C the pH in beaker F.
(a)
Interpretation:
The pH in beaker A and beaker B needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The pH in beaker A is less than (LT) the pH in B.
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
In beaker A, HI is a strong acid thus, the value of pH is less than the pH in beaker B which contains a weak acid
Therefore, the pH in beaker A is less than the pH in B.
(b)
Interpretation:
The pH in beaker C and beaker D needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The value of pH in beaker C is less than (LT) the pH in beaker D
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
The beaker C and D both contains strong base. The beaker C contains
Thus, the concentration of hydroxide ion in beaker D will be twice the concentration of hydroxide ion in beaker C.
If concentration of hydroxide ion increases, the value of pOH decreases and that of pH increases. Thus, the value of pH in beaker C is less than the pH in beaker D.
(c)
Interpretation:
The percent ionization in beaker A and beaker C needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The ionization percent of HF will be equal to (EQ) that of NaOH.
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
The percent ionization of a strong acid/base is more than a weak acid/base. Beaker A contains HF and beaker C contains NaOH.
Both HF and NaOH are strong and completely dissociates into their respective ions.
Therefore, ionization percent of HF will be equal to that of NaOH.
(d)
Interpretation:
The pH in beaker B and beaker E needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The value of pH will be less than 7 but the exact value cannot be calculated as it required more information. (MI)
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
The beaker B contains weak acid
Here,
The salt is formed from HCl and
(e)
Interpretation:
The pH in beaker E and beaker F needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The value of pH in beaker E is less than (LT) beaker F.
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
The beaker E contains
The Beaker F contains
Therefore, the value of pH in beaker E is less than beaker F.
(f)
Interpretation:
The pH in beaker C and beaker F needs to be compared.
Concept introduction:
The dissociation reaction of a weak acid is represented as follows:
The expression for the acid dissociation constant will be as follows:
Here,
The pH of the solution can be calculated as follows:
Here,
Answer to Problem 98QAP
The value of pH in beaker C is greater than (GT) pH in beaker F.
Explanation of Solution
According to the question, there are 6 beakers from beaker A to E.
The aqueous solutions in beakers are as follows:
Beaker A: 0.1 M, 100 mL HI which is a strong acid.
Beaker B: 0.1 M, 100 mL
Beaker C: 0.1 M, 100 mL
Beaker D: 0.1 M, 100 mL
Beaker E: 0.1 M, 100 mL
Beaker F: 0.1 M, 100 mL
Beaker C contains a strong acid the pH will be highly greater than 7 and beaker F contains a weak base the value of pH will be greater than 7 but less than the value in beaker C.
Therefore, the value of pH in beaker C is greater than pH in beaker F.
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Chapter 13 Solutions
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