Acid-Base Reactions - AP Chemistry
Card 0 of 1332
Determine the pH of an aqueous solution of 0.01 M acetic acid, 
. The pKa of acetic acid is 4.75.
Determine the pH of an aqueous solution of 0.01 M acetic acid,
Since acetic acid is a weak acid, it has a Ka that is rather small, we have to do a RICE table to determine the equilibrium amount of hydronium, H3O+ to then determine the pH.
R 
I 0.1 M - 0 0
C -x +x +x
E 0.1 -x x x
So first we need to change our pKa to a Ka
where 
therefore
= 
= 
If we assume that x is very small compared to 0.1...
Where 
(note: when solving using the quadratic we come up with the same answer)
So if 
Since acetic acid is a weak acid, it has a Ka that is rather small, we have to do a RICE table to determine the equilibrium amount of hydronium, H3O+ to then determine the pH.
R
I 0.1 M - 0 0
C -x +x +x
E 0.1 -x x x
So first we need to change our pKa to a Ka
where
If we assume that x is very small compared to 0.1...
Where
(note: when solving using the quadratic we come up with the same answer)
So if
Compare your answer with the correct one above
Which combination(s) would create a buffer solution?
I. Weak acid
II. Weak acid's conjugate base
III. Strong acid
IV. Strong base
V. Weak base
VI. Weak base's conjugate acid
Which combination(s) would create a buffer solution?
I. Weak acid
II. Weak acid's conjugate base
III. Strong acid
IV. Strong base
V. Weak base
VI. Weak base's conjugate acid
A buffer solution is formed from the equilibrium of a weak acid and its conjugate base, or from a weak base and its conjugate acid. It's ability to "buffer" the pH or keep it from changing in large amounts in from the switching between these two forms weak and its conjugate.
A buffer solution is formed from the equilibrium of a weak acid and its conjugate base, or from a weak base and its conjugate acid. It's ability to "buffer" the pH or keep it from changing in large amounts in from the switching between these two forms weak and its conjugate.
Compare your answer with the correct one above
You are in chemistry lab performing a titration. You were given 15 mL of an aqueous solution with an unknown concentration of acetic acid, 
to solve through titration with concentrated sodium hydroxide, 
. You know that the pKa of acetic acid is 4.75 and that your titrant is 0.1 M sodium hydroxide, 
.
The endpoint was determined at 10 mL of sodium hydroxide, 
. What is the pH after 5 mL of 
was added?
You are in chemistry lab performing a titration. You were given 15 mL of an aqueous solution with an unknown concentration of acetic acid,
The endpoint was determined at 10 mL of sodium hydroxide,
At the half end point, the 
. This can be determined by the Henderson-Hasselbalch equation if it is not clear.
Since the endpoint of the titration is that there are 10 mL of 0.1 M NaOH added, that means that there are 0.001 moles of acetic acid.
When 5 mL of NaOH is added, there are 0.0005 moles of acetic acid and 0.0005 moles of acetate formed.
Therefore pH= pKa
At the half end point, the
Since the endpoint of the titration is that there are 10 mL of 0.1 M NaOH added, that means that there are 0.001 moles of acetic acid.
When 5 mL of NaOH is added, there are 0.0005 moles of acetic acid and 0.0005 moles of acetate formed.
Therefore pH= pKa
Compare your answer with the correct one above
Determine which of these solution combinations form a buffer.
Determine which of these solution combinations form a buffer.
First to go through why the other ones are wrong:
Strong base + strong acid neutralizes and does not form a buffer solution
Strong base + weak base does not form a buffer - would need an acid
Strong base + weak acid = all weak acid converted to conjugate base
The correct answer is:
Strong base + weak acid = half converted to conjugate base with half leftover as weak acid, with all the components for a buffer
First to go through why the other ones are wrong:
Strong base + strong acid neutralizes and does not form a buffer solution
Strong base + weak base does not form a buffer - would need an acid
Strong base + weak acid = all weak acid converted to conjugate base
The correct answer is:
Strong base + weak acid = half converted to conjugate base with half leftover as weak acid, with all the components for a buffer
Compare your answer with the correct one above
Determine which combination of solutions would create a buffer solution.
Determine which combination of solutions would create a buffer solution.
For all the other options there is no ammonium leftover with which to serve as the weak acid in the buffer system, the ammonium is all used up and converted to ammonia. However in the correct answer choice, there is enough ammonium leftover after the reaction with the sodium hydroxide.
For all the other options there is no ammonium leftover with which to serve as the weak acid in the buffer system, the ammonium is all used up and converted to ammonia. However in the correct answer choice, there is enough ammonium leftover after the reaction with the sodium hydroxide.
Compare your answer with the correct one above
Determine which solution(s) will yield a buffer solution.
I. 10 mL of 0.5 M HCl + 20 mL of 0.5 M acetate
II. 10 mL of 0.5 M HCl + 10 mL of 0.5 M acetate
III. 10 mL of 0.5 M HCl + 10 mL of 1.0 M acetate
IV. 10 mL of 0.5 M HCl + 10 mL of 1.5 M acetate
Determine which solution(s) will yield a buffer solution.
I. 10 mL of 0.5 M HCl + 20 mL of 0.5 M acetate
II. 10 mL of 0.5 M HCl + 10 mL of 0.5 M acetate
III. 10 mL of 0.5 M HCl + 10 mL of 1.0 M acetate
IV. 10 mL of 0.5 M HCl + 10 mL of 1.5 M acetate
These answers are correct because the two components needed to create a buffer solution are a weak acid and its conjugate base, or a weak base and its conjugate acid. In these cases, the first reaction to occur upon addition of the strong acid is the formation of the conjugate acid, acetic acid.
If the amount of initial 
is greater than HCl, then we will have some 
left over to act as a buffer with the created conjugate acid. This can be through a greater volume, or through a higher concentration as shown in the correct answers.
These answers are correct because the two components needed to create a buffer solution are a weak acid and its conjugate base, or a weak base and its conjugate acid. In these cases, the first reaction to occur upon addition of the strong acid is the formation of the conjugate acid, acetic acid.
If the amount of initial
Compare your answer with the correct one above
Which of the following acid and base pairs are capable of acting as a buffer?
Which of the following acid and base pairs are capable of acting as a buffer?
In this question, we're presented with a variety of acid/base pairs and we're asked to identify which one could act as a buffer.
Remember that a buffer is a pair of acid and its conjugate base that acts to resist substantial changes in pH. In order for a buffer to work, the acid base pair needs to exist in equilibrium. This way, when the pH of the solution changes, the equilibrium of the acid/base reaction will shift, such that the pH will not change drastically.
To have an acid/base pair in equilibrium, we'll need to look for a pair that contains a weak acid. Acids like 
and 
are so strong that they will dissociate completely. Of the answer choices shown, only the carbonic acid/bicarbonate system (
and 
) exists in equilibrium. Thus, this is the correct answer.
In this question, we're presented with a variety of acid/base pairs and we're asked to identify which one could act as a buffer.
Remember that a buffer is a pair of acid and its conjugate base that acts to resist substantial changes in pH. In order for a buffer to work, the acid base pair needs to exist in equilibrium. This way, when the pH of the solution changes, the equilibrium of the acid/base reaction will shift, such that the pH will not change drastically.
To have an acid/base pair in equilibrium, we'll need to look for a pair that contains a weak acid. Acids like
Compare your answer with the correct one above
Which of the following techniques will decrease the pH of a solution?
Which of the following techniques will decrease the pH of a solution?
Increasing the concentration of protons of a solution will make the solution more acidic; therefore, it lowers the solution’s pH. Decreasing the concentration of protons will make the solution more basic, raising the pH. Adding more acid of the same molarity of the original solution will not increase the concentration of protons and will not increase acidity or lower the pH. Increasing the amount of hydroxide ions will make the solution more basic and raise the pH. Increasing the amount of solvent will lower the concentration, affecting molarity and not lowering the pH.
Increasing the concentration of protons of a solution will make the solution more acidic; therefore, it lowers the solution’s pH. Decreasing the concentration of protons will make the solution more basic, raising the pH. Adding more acid of the same molarity of the original solution will not increase the concentration of protons and will not increase acidity or lower the pH. Increasing the amount of hydroxide ions will make the solution more basic and raise the pH. Increasing the amount of solvent will lower the concentration, affecting molarity and not lowering the pH.
Compare your answer with the correct one above
Determine the pH of a solution that is 
.
Determine the pH of a solution that is
Since 
is a strong acid, the concentration of 
is equal to the concentration of the acid itself.
Thus, 
.
Recall how to find the pH of a solution:
Plug in the given hydronium ion concentration to find the pH of the given solution.
Remember to maintain the correct number of significant figures.
Since
Thus,
Recall how to find the pH of a solution:
Plug in the given hydronium ion concentration to find the pH of the given solution.
Remember to maintain the correct number of significant figures.
Compare your answer with the correct one above
Find the pH for a solution that is 
by mass. Assume a density of 
for the solution.
Find the pH for a solution that is
Start by assuming that there is 
liter of the solution. From this, we can use the given density to find the mass of the solution.
Next, find the mass of 
that is present in the solution.
Now, find the number of moles of 
that is present in the solution.
Since we initially assumed that we had 
liter of the solution, we now also know the concentration of 
in this solution.
Since 
is a strong acid, the concentration of hydronium ions in the solution will be the same as the concentration of 
.
Recall how to find the pH of a solution.
Start by assuming that there is
Next, find the mass of
Now, find the number of moles of
Since we initially assumed that we had
Since
Recall how to find the pH of a solution.
Compare your answer with the correct one above
Find the pH of a solution that is 
by mass. Assume a density of 
for the solution.
Find the pH of a solution that is
Start by assuming that there is 
liter of the solution. From this, we can use the given density to find the mass of the solution.
Next, find the mass of 
that is present in the solution.
Now, find the number of moles of 
that is present in the solution.
Since we initially assumed that we had 
liter of the solution, we now also know the concentration of 
in this solution.
Since 
is a strong acid, the concentration of hydronium ions in the solution will be the same as the concentration of 
.
Recall how to find the pH of a solution.
Start by assuming that there is
Next, find the mass of
Now, find the number of moles of
Since we initially assumed that we had
Since
Recall how to find the pH of a solution.
Compare your answer with the correct one above
Put the following acids in order of their INCREASING acid strength: HCl, HS, HBr, H2Se.
Put the following acids in order of their INCREASING acid strength: HCl, HS, HBr, H2Se.
Acid strength increases from left to right across a period and increases going down a group.
Acid strength increases from left to right across a period and increases going down a group.
Compare your answer with the correct one above
Which of the following can be used in a buffer solution?
Which of the following can be used in a buffer solution?
For a buffer solution, you need a weak acid and its conjugate base, or a weak base and its conjugate acid. HCO3 from the NaHCO3 and CO3– from K2CO3 are this pair.
For a buffer solution, you need a weak acid and its conjugate base, or a weak base and its conjugate acid. HCO3 from the NaHCO3 and CO3– from K2CO3 are this pair.
Compare your answer with the correct one above
Put the following acids in order of their INCREASING acid strength: HI, HCl, HBr, HF.
Put the following acids in order of their INCREASING acid strength: HI, HCl, HBr, HF.
Larger halogen size leads to greater acidity because of weaker H-X interactions.
Larger halogen size leads to greater acidity because of weaker H-X interactions.
Compare your answer with the correct one above
Which of the following would best buffer a solution from a pH of 4 to 6?
Which of the following would best buffer a solution from a pH of 4 to 6?
A weak acid/base best buffers about 1 pH point above and below its pKa. The pKA closest to the middle of 4 and 6 (so want as close to 5) is acetic acid at 4.7.
A weak acid/base best buffers about 1 pH point above and below its pKa. The pKA closest to the middle of 4 and 6 (so want as close to 5) is acetic acid at 4.7.
Compare your answer with the correct one above
A buffer using acetic acid (pKa=4.76) is titrated with NaOH. What is the pH at half the equivalence point?
A buffer using acetic acid (pKa=4.76) is titrated with NaOH. What is the pH at half the equivalence point?
The pH at half the equivalence point is equal to the pKa of the acid.
The pH at half the equivalence point is equal to the pKa of the acid.
Compare your answer with the correct one above
Which of the following solutions has the greatest buffering capacity?
Which of the following solutions has the greatest buffering capacity?
Nitric Acid is a strong acid and can't buffer. Rubidium Hydroxide is a strong base and thus can't buffer. Of the remaining, both are weak acids, but the one with a greater concentration has a greater buffering capacity.
Nitric Acid is a strong acid and can't buffer. Rubidium Hydroxide is a strong base and thus can't buffer. Of the remaining, both are weak acids, but the one with a greater concentration has a greater buffering capacity.
Compare your answer with the correct one above
To create a buffer solution, you can use a weak acid and .
To create a buffer solution, you can use a weak acid and .
The definition of a buffer solution is that it contains a weak acid and its conjugate base, or a weak base and its conjugate acid. Since we are starting with a weak acid in this case, we need its conjugate base.
The definition of a buffer solution is that it contains a weak acid and its conjugate base, or a weak base and its conjugate acid. Since we are starting with a weak acid in this case, we need its conjugate base.
Compare your answer with the correct one above
Which of the following will increase the pH of an 
buffer solution?
I. Removing carbonic acid
II. Adding sodium bicarbonate
Which of the following will increase the pH of an
I. Removing carbonic acid
II. Adding sodium bicarbonate
To answer this question we need to look at the reaction below:
An increase in the pH will result in a decrease in the concentration of hydrogen ions (
). Using Le Chatelier’s principle we can find out which answer choices will decrease 
.
Removing carbonic acid will decrease the concentration of 
. To maintain equilibrium, the reaction will shift to the left and make more reactants from products; therefore, there will be a decrease in the 
and an increase in pH.
Recall that salts like sodium bicarbonate, or 
, will dissociate in water and form ions. Sodium bicarbonate will form sodium (
) and bicarbonate (
) ions. This side reaction will result in an increase in the bicarbonate ion concentration. Le Chatelier’s principle will shift the equilibrium of the given reaction to the left and, therefore, decrease the 
. Adding sodium bicarbonate will increase the pH.
To answer this question we need to look at the reaction below:
An increase in the pH will result in a decrease in the concentration of hydrogen ions (
Removing carbonic acid will decrease the concentration of
Recall that salts like sodium bicarbonate, or
Compare your answer with the correct one above
Which of the following combinations cannot be used to produce a buffer solution?
Which of the following combinations cannot be used to produce a buffer solution?
Buffer solutions can be made via two methods. The first method involves adding equal amounts of a weak acid and a salt of its weak conjugate base (or vice versa). The second methods involves adding a weak acid and a half equivalent of a strong base (or vice versa).
is a weak acid and 
is a salt of its weak conjugate base; therefore, this can form a buffer.
is a weak base and 
is a salt of its weak conjugate acid; this can also form a buffer. Note that this is the converse of the first method (weak base with salt of weak acid), but it can still form a buffer solution.
is a strong acid and 
is a weak base; therefore, adding 
and a half equivalent of 
will create a buffer solution. This is the converse of the second method (adding a weak base to a half equivalent of strong acid).
and 
are both strong reagents (acid and base, respectively); therefore, they cannot form a buffer solution.
Buffer solutions can be made via two methods. The first method involves adding equal amounts of a weak acid and a salt of its weak conjugate base (or vice versa). The second methods involves adding a weak acid and a half equivalent of a strong base (or vice versa).
Compare your answer with the correct one above