Calculating pH of Strong and Weak Acids with 10^-7 M Concentration - Explained

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In summary, the method for calculating the pH of a strong and weak acid with a concentration of 10^-7 M involves taking into consideration the change in concentration of H+ from water. This is because the amount of H+ from water is not negligible compared to the H+ that dissociates from the acid. The dissociation of water is suppressed by the acid, resulting in a total concentration of H+ that is the sum of H+ from water and the acid. This requires solving a quadratic equation to determine the pH. There is no simpler method to solve this problem.
  • #1
benzun_1999
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Can anyone tell me how to calculate pH of an strong and weak acid with conc [tex]10^-^7 M[/tex] . Please just explain the method. i read a little about it. Why is it necessary to take into consideration the change in conc of [tex]H^+[/tex] from water?

-Benzun
 
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  • #2
benzun_1999 said:
Why is it necessary to take into concideration the change in conc of [tex]H^+[/tex] from water?

That is because the amount of H+ which comes from water is now not negligible when compared to the H+ which dissociates from the acid.

For example, what is the pH of 10^-8 M of HCl ?

What happens is that, the dissociation of H20 is suppressed by HCl by the common ion-efect.

So if you consider the dissociation of water
H20----> H+ + OH-
let x be the conc of H+
so, the total conc of H+ is x (from water) + 10^-8 (from the strong acid HCl). And the conc of OH- is x(from water). You also know Kw. So, can you take it from here?
 
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  • #3
ok understood but is there some easy and clean way to proceed in this sum without getting quadratic equation?
 
  • #4
No. You will have to solve the quadratic.
 

1. What is the meaning of "PH of 10^-7 M acid"?

The PH of 10^-7 M acid refers to the measurement of the acidity or basicity of a solution with a concentration of 10^-7 moles per liter (M). This concentration is also known as a neutral solution, as it has an equal number of hydrogen ions (H+) and hydroxide ions (OH-) present.

2. How is the PH of 10^-7 M acid calculated?

The PH of a solution can be calculated using the formula PH = -log[H+], where [H+] represents the concentration of hydrogen ions in the solution. In this case, the concentration of hydrogen ions in a 10^-7 M acid solution is equal to 10^-7 moles per liter, resulting in a PH of 7.

3. Is a PH of 10^-7 M acid considered acidic or basic?

A PH of 10^-7 M acid is considered neutral, as it falls in the middle of the PH scale which ranges from 0 (most acidic) to 14 (most basic). A solution with a PH of 7 is neither acidic nor basic, and is often referred to as a neutral solution.

4. What are some common examples of solutions with a PH of 10^-7 M acid?

Some common examples of solutions with a PH of 10^-7 M acid include pure water, human blood, and tears. These solutions all have a neutral PH due to the balance of hydrogen ions and hydroxide ions present.

5. How does the PH of 10^-7 M acid impact living organisms?

The PH of 10^-7 M acid is crucial for the survival of living organisms, as it is necessary for maintaining a neutral internal environment. Any significant changes in the PH of the body can disrupt biological processes and lead to health problems. For example, a decrease in PH can result in acidosis, while an increase can cause alkalosis.

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