Concept explainers
a Draw a pH titration curve that represents the titration of 50.0 mL of 0.10 M NH3 by the addition of 0.10 M HCl from a buret. Label the axes and put a scale on each axis. Show where the equivalence point and the buffer region are on the titration curve. You should do calculations for the 0%, 30%, 50%, and 100% titration points. b Is the solution neutral, acidic, or basic at the equivalence point? Why?
(a)
Interpretation:
For titration of 50.0 mL of 0.10 M
A pH titration curve showing the equivalence point and buffer region has to be drawn
- (a) The pH of the titration points for the 0%, 30 %, 50% and 100% has to be calculated
- (b) Whether the solution at the equivalence point is neutral, acidic or basic has to be explained
Concept Introduction:
Equivalence point:
The equivalence point in titration is the point where the amount of standard titrant solution (in moles) and the unknown concentration analyte solution (in moles) becomes equal.
In other words, the equivalence point is the point obtained in a titration once a stoichiometric amount of reactant has been added.
Relationship between pH and pOH:
Answer to Problem 16.119QP
A pH titration curve showing the equivalence point and buffer region is given in Figure 1 as follows,
Figure 1
(a)
The pH at the 0% titration point is 11.13
The pH at the 30% titration point is 9.62
The pH at the 50% titration point is 9.26
The pH at the 100% titration point is 5.28
(b)
The solution at the equivalence point is acidic
Explanation of Solution
To Calculate: The pH of the titration points for the 0%, 30 %, 50% and 100%
Given data:
Titration of 0.10 M
pH at the 0% titration point:
Construct an equilibrium table with x as unknown concentration
|
|||
Initial |
0.10
0.10-x |
0.00 | 0.00 |
Change |
|
|
|
Equilibrium |
x | x |
Substitute equilibrium concentrations into the equilibrium-constant equation.
The
Assume x is negligible compared to 0.10 M
Therefore, the concentration of hydroxide ion
In the end, pH is calculated as follows,
Therefore, the pH at the 0% titration point is 11.13
pH at the 30% titration point:
For convenience, express the concentrations as percents.
Substitute the concentrations into the equilibrium expression.
Therefore, the concentration of hydroxide ion
In the end, pH is calculated as follows,
Therefore, the pH at the 30% titration point is 9.62
pH at the 50% titration point:
The pH is calculated as follows,
Therefore, the pH at the 50% titration point is 9.26
pH at the 100% titration point:
As a result of titration
The
Therefore,
Construct an equilibrium table with x as unknown concentration
|
|||
Initial |
0.0500
0.0500-x |
0.00 | 0.00 |
Change |
|
|
|
Equilibrium |
x | x |
Now, calculate
Substitute into the equilibrium constant expression.
Here, x gives the concentration of hydronium ion,
The pH is calculated as follows,
Therefore, the pH at the 100% titration point is 5.28
The pH at the 0% titration point was calculated as 11.13
The pH at the 30% titration point was calculated as 9.62
The pH at the 50% titration point was calculated as 9.26
The pH at the 100% titration point was calculated as 5.28
(b)
Interpretation:
For titration of 50.0 mL of 0.10 M
A pH titration curve showing the equivalence point and buffer region has to be drawn
- (a) The pH of the titration points for the 0%, 30 %, 50% and 100% has to be calculated
- (b) Whether the solution at the equivalence point is neutral, acidic or basic has to be explained
Concept Introduction:
Equivalence point:
The equivalence point in titration is the point where the amount of standard titrant solution (in moles) and the unknown concentration analyte solution (in moles) becomes equal.
In other words, the equivalence point is the point obtained in a titration once a stoichiometric amount of reactant has been added.
Relationship between pH and pOH:
Answer to Problem 16.119QP
A pH titration curve showing the equivalence point and buffer region is given in Figure 1 as follows,
Figure 1
(a)
The pH at the 0% titration point is 11.13
The pH at the 30% titration point is 9.62
The pH at the 50% titration point is 9.26
The pH at the 100% titration point is 5.28
(b)
The solution at the equivalence point is acidic
Explanation of Solution
To Explain: Whether the solution at the equivalence point is neutral, acidic or basic
As a result of titration
Ammonium chloride salt is the salt of weak base and a strong acid
Therefore, the given solution is acidic
The solution at the equivalence point was found as acidic
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Chapter 16 Solutions
General Chemistry - Standalone book (MindTap Course List)
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