Test question: Water has pH of 7. Which solution has a [H+] concen

In summary, the conversation discusses the relationship between pH and [H+] concentration, specifically how a 100 fold difference in [H+] concentration only results in a 1 step difference in pH. The correct answer to the given question is B (milk with a pH of 6), which has a [H+] concentration of 10^-6, resulting in a 1 step decrease from pH 7. The summary also mentions that the original answer of A (bananas with a pH of 5) is also correct, as it has a [H+] concentration of 10^-5, resulting in a 2 step decrease from pH 7.
  • #1
Lo.Lee.Ta.
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Test question: "Water has pH of 7. Which solution has a [H+] concen.."

1.
testquestionpH7_zps2bd23879.jpg



2. First of all, increasing [H+] concentration will give something more acidic. Since every jump between pH numbers is a 10 fold difference, I thought that to make a 100 fold difference, you would have to do 10x10, which would cause the pH number to go down by two steps.

That's why I chose A (bananas with a pH of 5).

The actual answer is B (milk with a pH of 6).

How does pH decrease by only 1 step?
Would you please explain this to me?

Thank you so much! :)
 
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  • #2


IMHO your answer (pH 5, bananas) is a correct one.

At pH 5 [itex][H^+] = 10^{-5}[/itex], at pH 7 [itex][H^+] = 10^{-7}[/itex], [itex]\frac {10^{-5}}{10^{-7}} = 100[/itex].
 

1. What does a pH of 7 mean for water?

A pH of 7 for water means that the concentration of hydrogen ions ([H+]) is equal to the concentration of hydroxide ions ([OH-]). This indicates that the water is neutral, neither acidic nor basic.

2. How is the pH of a solution determined?

The pH of a solution is determined by measuring the concentration of hydrogen ions ([H+]) using a pH meter or pH strips. The more hydrogen ions present in a solution, the lower the pH will be. A pH of 7 is considered neutral, with lower values indicating acidity and higher values indicating basicity.

3. Is a pH of 7 always neutral?

In general, a pH of 7 is considered neutral. However, this may vary depending on the substance being measured. For example, a pH of 7 for stomach acid would be considered acidic, while a pH of 7 for household bleach would be considered basic.

4. How does the pH of water affect living organisms?

The pH of water is essential for the survival of living organisms. Most organisms have a specific pH range in which they can thrive, and any significant changes in the pH of their environment can be harmful. For example, a decrease in the pH of water can make it more acidic, which can be harmful to aquatic life.

5. Can the pH of water change?

Yes, the pH of water can change. It can be influenced by a variety of factors, including the presence of dissolved minerals, gases, and organic matter. Human activities can also impact the pH of water, such as pollution and acid rain, which can lower the pH of water and make it more acidic.

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