Question 1

Which of the following solutions is the most acidic?
A)a solution with a pH = 14
B)a solution with a pH = 12
C)a solution with a pH = 7
D)a solution with a pH = 13
E)All of the solutions are basic.

Accepted Answer

A solution with a pH of 7 is neutral, and all other options are basic (pH > 7). Among the given options, the neutral solution (pH = 7) is the most acidic.

Question 2

As the pH increases, the hydroxide ion concentration ________. A)goes down B)gets larger C)starts to affect the H⁺ concentration D)starts to decrease because it is reacting with the excess hydronium ions E)stays constant

Accepted Answer

As the pH of a solution increases, the concentration of hydroxide ions (OH-) also increases. This is because pH is a measure of the concentration of hydronium ions (H3O+) in a solution, and the concentration of hydronium ions and hydroxide ions are inversely proportional to each other in water. As the concentration of H3O+ decreases, the concentration of OH- increases.

Question 3

If the pH of a solution is 10, what is the hydroxide ion concentration? A)1 × 10^-4M B)4 M C)14 M D)-14 M E)- 1 × 10¹⁴M

Accepted Answer

To find the hydroxide ion concentration, we can use the formula: pH + pOH = 14. Since the pH of the solution is 10, we can calculate that the pOH is 4 (14 - 10 = 4). From there, we can use the formula for pOH to find the hydroxide ion concentration: pOH = -log[OH-]. Rearranging the formula gives: [OH-] = 10^-pOH. Plugging in the value of pOH (4) gives: [OH-] = 1×10^-4 M.

Question 4

Why do we use the pH scale to indicate the acidity of a solution rather than simply stating the concentration of hydronium ions?
A)It includes the concentration of hydronium and hydroxide ions.
B)It is used because the general public understands it.
C)It is more accurate to use the pH scale.
D)It is more convenient, since the concentration of hydronium ions is so small.

Accepted Answer

The pH scale is used because it is more convenient due to the very small concentration of hydronium ions in solutions. The scale provides a simpler way to express these concentrations, which can vary widely and be extremely small, making direct numerical representation cumbersome.

Question 5

If the pH of a solution is 10, what is the hydronium ion concentration? A)1 × 10^-10M B)1 × 10¹⁰M C)10 M D)-10 M E)- 1 × 10¹⁰M

Accepted Answer

The hydronium ion concentration in a solution with a pH of 10 is 1 × 10^-10 M. This is because pH is calculated as -log[H3O+], so if pH = 10, then [H3O+] = 10^-10 M.

Question 6

When the hydronium ion concentration equals 1 mole per liter, what is the pH of the solution? Is the solution acidic or basic?
A)pH = 0, this is an acidic solution.
B)pH = 1, this is an acidic solution.
C)pH = 10, this is a basic solution.
D)pH = 7, this is a neutral solution.

Accepted Answer

The pH is calculated as the negative logarithm (base 10) of the hydronium ion concentration. When the concentration is 1 mole per liter, the pH = -log(1) = 0. Since pH less than 7 is considered acidic, the solution is acidic.

Question 7

If the pH of a solution was 7 and you were to increase the hydroxide ion concentration 100x, what would the pH be? A)9 B)5 M C)1 × 10^-5 M D)700 M E)5

Accepted Answer

Increasing the hydroxide ion concentration in a solution shifts the pH towards the basic side. A pH of 7 is neutral. Increasing the hydroxide ion concentration 100 times would decrease the hydrogen ion concentration by the same factor, moving the pH up by 2 units (since pH is logarithmic), resulting in a pH of 9.

Question 8

If the pH of a solution was 7 and you were to increase the hydronium ion concentration 1000x, what would the pH be? A)4 B)4 M C)1 × 10^-4 M D)7,000 M E)10

Accepted Answer

The pH scale is logarithmic, meaning that each whole number change represents a tenfold change in hydronium ion concentration. Increasing the hydronium ion concentration by 1000 times (or 10^3 times) would decrease the pH by 3 units, from 7 to 4.

Question 9

If you had a 1 M solution of a weak acid what would be its pH?
A)1
B)6
C)7
D)8
E)13

Accepted Answer

A 1 M solution of a weak acid will have a pH less than 7 but greater than 1, as weak acids do not completely dissociate in water. A pH of 6 is a reasonable estimate for a weak acid solution.

Question 10

If you had a 1 M solution of a strong base what would be its pH?
A)1
B)6
C)7
D)8
E)13

Accepted Answer

A strong base is a compound that completely dissociates in water to form hydroxide ions (OH-). A 1 M solution of a strong base would have a concentration of 1 M OH-. Using the formula for the pOH of a solution, we find that pOH = -log[OH-]. Thus, pOH = -log(1) = 0. 
To find the pH of the solution, we use the formula pH + pOH = 14. 
pH + 0 = 14 
pH = 14 
Therefore, the pH of a 1 M solution of a strong base would be 14 - 0 = 14. 
Note that a pH of 14 is very basic, so the answer is E) 13.

Question 11

What does the value of  say about the extent to which water molecule react with themselves?
A)Because the value of  is so small, the extent to which water ionizes is quite large.
B)Because the value of  is so small, the extent to which water ionizes is quite small.
C)Water molecules react with themselves at a constant rate, never increasing or decreasing.
D)When an acid is added to water, the value of  will decrease.

Accepted Answer

The given value is a random hexadecimal number that has no relation to the extent of water molecule reactions. Therefore, option A, C, and D are incorrect. Option B is the most appropriate answer as it states that the value is small which suggests that the extent to which water ionizes is quite small.

Question 12

If you had a 1 M solution of a weak base what would be its pH?
A)1
B)6
C)7
D)8
E)13

Accepted Answer

A 1 M solution of a weak base would have a basic pH, but since it's a weak base, it wouldn't be as strong in its basic properties as a strong base. An estimate for the pH for a 1 M solution of a weak base would be around 8. Therefore, the best choice is D.

Question 13

Which of the following solutions is the most acidic?
A)a solution with a pH = 14
B)a solution with a pH = 10
C)a solution with a pH = 7
D)a solution with a pH = 4
E)All of the solutions are basic.

Accepted Answer

The lower the pH value, the higher the acidity of the solution. Therefore, a solution with a pH = 4 is more acidic than a solution with a pH = 7 or pH = 10, and it is extremely acidic compared to a solution with a pH = 14, which is actually a basic solution.

Question 14

Along with the pH scale, there is the pOH scale, which indicates the level of "basicity" in a solution. Accordingly, pOH = -log[OH^-]. What is the sum of the pH and the pOH of a solution always equal to? A)the negative of the product of the hydronium and hydroxide ions B)the negative log of , which is 14 C)The sum would equal 7, since that would be neutral for pH and pOH. D)It is not constant because it depends on the acid/base solution in question.

Accepted Answer

The pH scale and the pOH scale are complementary; the sum of the pH and the pOH of a solution should always equal 14, which is the negative log of the product of the hydronium and hydroxide ions (10^-14). Therefore, the correct answer is (B) the negative log of 10^-14, which is 14.

Question 15

What would be the concentration of hydronium ions in a solution that had a pH = -3? Why would such a solution be impossible to prepare?
A)Concentration of   = 3 M. It is impossible because it is hard to measure such a small amount of hydronium ions accurately.
B)Concentration of   = 30 M. It is impossible because pH can not be negative.
C)Concentration of   =  M. It is impossible because any container used to hold the acid would immediately corrode.
D)Concentration of   =  M. It is impossible because only so much acid can dissolve in water before the solution becomes saturated.

Accepted Answer

The answer of What would be the concentration of hydronium...

Question 16

If you had a 1 M solution of a strong acid what would be its pH?
A)1
B)6
C)7
D)8
E)13

Accepted Answer

A strong acid at a concentration of 1 M has a pH of 1. This is because the concentration of H+ ions in the solution is very high, resulting in a low pH value.

Question 17

Pour vinegar onto beach sand from the Caribbean and the result is a lot of froth and bubbles. Pour vinegar onto beach sand from California, however, and nothing happens. Why?
A)Beaches in tropical climates generally have remnants of volcanic deposit not present in California sand. These deposits contain soil with organic residue. Vinegar's acetic acid reacts with organic matter.
B)The pH of the warm sands of tropical waters is well into the basic range, unlike the beach sand in California. Therefore, the acidic vinegar reacts with Caribbean beach sand but not with sand from California.
C)Beach sand from the Caribbean and many other tropical climates is made primarily of the calcium carbonate remains of coral and shelled creatures. Vinegar is an acid and the calcium carbonate is a base.
D)Caribbean beach sand contains deposits from the mouth of the Mississippi river which carries with it a great deal of contamination from urban waste. These warm water contaminates react with the acid in vinegar.

Accepted Answer

Beach sand from the Caribbean and many other tropical climates is made primarily of the calcium carbonate remains of coral and shelled creatures. Vinegar is an acid and the calcium carbonate is a base. Therefore, vinegar reacts with Caribbean beach sand but not with sand from California.

Question 18

The amphoteric reaction between two water molecules is endothermic, which means that this reaction requires the input of energy in order to proceed: Energy +  O +  O →   + O  The warmer the temperature of the water, the more thermal energy is available for this reaction, and the more hydronium and hydroxide ions are formed. Based on this information, should the value of  be expected to increase, decrease, or stay the same with increasing temperature?
A)The value of  will stay the same, since it is a constant.
B)The value of  will decrease, since there are more hydronium ions than hydroxide ions.
C)The value of  will increase since the rise in temperature allows for a higher concentration of both ions.
D)The value of  will decrease since there are more hydroxide ions than hydronium ions.

Accepted Answer

The amphoteric reaction between water molecules generates both hydronium and hydroxide ions through the equation: Energy + H2O + H2O ⇌ H3O+ + OH-. As mentioned, the reaction is endothermic, meaning that it requires energy input to happen. Therefore, at higher temperatures, there is greater thermal energy available, which favors the breaking of H2O and the formation of H3O+ and OH-. This increases the concentration of both ions, leading to an increase in the value of Kw.

Question 19

What happens to the pH of an acidic solution as water is added?
A)The pH is not influenced by the addition of water.
B)The pH will decrease as the solution becomes more dilute.
C)The pH will increase as the solution becomes more dilute.
D)The pH will decrease since more hydronium ions are produced from the water.

Accepted Answer

As water is added to an acidic solution, the concentration of hydronium ions decreases, resulting in a decrease in acidity. This causes the pH to increase as the solution becomes more dilute.

Question 20

When the hydronium ion concentration equals 10 moles per liter, what is the pH of the solution? Is the solution acidic or basic?
A)pH = 0, this is an acidic solution.
B)pH = 1, this is an acidic solution.
C)pH = -0.301, this is an acidic solution.
D)pH = 7, this is a neutral solution.

Accepted Answer

The pH is calculated using the formula pH = -log[H3O+]. For a hydronium ion concentration of 10 moles per liter, pH = -log(10) = -1. Since the pH is negative, it indicates a highly acidic solution. However, the closest choice given is pH = -0.301, which is still acidic.

Quiz 10: Acids and Bases in Our Environment

Which of the following solutions is the most acidic?

As the pH increases, the hydroxide ion concentration ________.

If the pH of a solution is 10, what is the hydroxide ion concentration?

Why do we use the pH scale to indicate the acidity of a solution rather than simply stating the concentration of hydronium ions?

If the pH of a solution is 10, what is the hydronium ion concentration?

When the hydronium ion concentration equals 1 mole per liter, what is the pH of the solution? Is the solution acidic or basic?

If the pH of a solution was 7 and you were to increase the hydroxide ion concentration 100x, what would the pH be?

If the pH of a solution was 7 and you were to increase the hydronium ion concentration 1000x, what would the pH be?

If you had a 1 M solution of a weak acid what would be its pH?

If you had a 1 M solution of a strong base what would be its pH?

What does the value of say about the extent to which water molecule react with themselves?

If you had a 1 M solution of a weak base what would be its pH?

Which of the following solutions is the most acidic?

Along with the pH scale, there is the pOH scale, which indicates the level of "basicity" in a solution. Accordingly, pOH = -log[OH-]. What is the sum of the pH and the pOH of a solution always equal to?

What would be the concentration of hydronium ions in a solution that had a pH = -3? Why would such a solution be impossible to prepare?

If you had a 1 M solution of a strong acid what would be its pH?

Pour vinegar onto beach sand from the Caribbean and the result is a lot of froth and bubbles. Pour vinegar onto beach sand from California, however, and nothing happens. Why?

What happens to the pH of an acidic solution as water is added?

When the hydronium ion concentration equals 10 moles per liter, what is the pH of the solution? Is the solution acidic or basic?

Along with the pH scale, there is the pOH scale, which indicates the level of "basicity" in a solution. Accordingly, pOH = -log[OH^-]. What is the sum of the pH and the pOH of a solution always equal to?