2. Which of the following statements are true about a strong base and a weak base at a pH of 11?
HCl will not bring the pH of either solution to pH 7.
Both bases require the same amount of HCl to reach pH 7 because they are both at the same initial pH.
The weak base will require less HCl to bring the pH to 7 than the strong base.
The strong base will require less HCl to bring the pH to 7 than the weak base.
I think it would be the last option, as a stronger base will need less of an acid to bring the pH to a neutral 7. Is this correct?
Yes
The correct statement is:
- The strong base will require less HCl to bring the pH to 7 than the weak base.
Explanation: A strong base has a higher concentration of hydroxide ions (OH-) and therefore a higher pH compared to a weak base. To neutralize the base and bring the pH to 7, you would need to add an acid, in this case HCl. Since the strong base has a higher pH, it is already closer to pH 7, requiring less HCl to reach the neutral pH. The weak base, on the other hand, has a lower pH and requires more acid (HCl) to reach pH 7.
To determine which statements are true about a strong base and a weak base at a pH of 11, we need to understand the concepts of pH, bases, and the strength of bases.
pH is a measure of how acidic or basic a solution is. It is on a scale of 0 to 14, with 7 being neutral. A pH below 7 indicates acidity, while a pH above 7 indicates alkalinity (basicity).
Bases are substances that can accept protons (H+) and can increase the concentration of hydroxide ions (OH-) in a solution. Bases can be classified as strong or weak based on their ability to dissociate in water.
Now let's evaluate each statement:
1) HCl will not bring the pH of either solution to a pH of 7.
This statement is true. HCl is a strong acid that will readily donate protons to neutralize bases. Since both the strong base and weak base have a pH of 11, they are already near the alkaline end of the pH scale. Therefore, adding HCl will lower their pH, but it will not bring them to a neutral pH of 7.
2) Both bases require the same amount of HCl to reach pH 7 because they are both at the same initial pH.
This statement is false. While it is true that both the strong base and weak base have the same initial pH of 11, their strength as bases is different. Strong bases fully dissociate in water and release more hydroxide ions, while weak bases partially dissociate and release fewer hydroxide ions. Therefore, the weak base will require less HCl to reach a pH of 7 compared to the strong base.
3) The weak base will require less HCl to bring the pH to 7 than the strong base.
This statement is true. As explained earlier, a weak base releases fewer hydroxide ions compared to a strong base. Therefore, it will require less HCl to neutralize the weak base and bring its pH to 7.
4) The strong base will require less HCl to bring the pH to 7 than the weak base.
This statement is false. As mentioned before, a strong base releases more hydroxide ions, making it more alkaline. Consequently, a strong base would require more HCl to neutralize it and bring its pH to 7 compared to a weak base.
In summary, the correct statements are:
- HCl will not bring the pH of either solution to pH 7.
- The weak base will require less HCl to bring the pH to 7 than the strong base.