How do you calculate the pH of a strong acid or base?

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How do you calculate the pH of a strong acid or base?

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Answer 1 · 2017-02-16T05:01:34

You calculate it normally -> find the concentration of the acid, transfer the concentration and insert the value in a logarithmic equation.

Explanation:

To calculate pH in general, you need the concentration of hydrogen ions in the compound.

Strong acids are acids with a pH of less than 4-ish while weak acids have a pH of 4-ish to 7.0.

In order to find mols, we typically use stoichiometry and the concentration formula $(n = c v)$ $(n=cv)$ .

When you find concentration of an acid, you need to transfer the concentration to each individual element.

E.g.

$H_{2} S O_{4} (a q) \to 2 H^{+} (a q) + S O_{4}^{2 -} (a q)$ $H_"2"SO_"4" (aq) -> 2H^+ (aq) + SO_"4"^(2-) (aq)$

$H_{2} S O_{4}$ $H_"2"SO_"4"$ has a concentration of $0.25$ $0.25$ mol/L. You transfer the concentration just like how you would transfer mols in stoichiometry. THIS IS THE ONLY TIME YOU CAN TRANSFER CONCENTRATION

As a result, your hydrogen concentration is $0.5$ $0.5$ mol/L.

Use the logarithm function to find pH:

$p H = - log [H^{+}]$ $pH = -log [H^+]$

$= - log [0.5]$ $=-log[0.5]$

$= 0.301029995$ $=0.301029995$

$= 0.3$ $=0.3$

In this example, the pH of $H_{2} S O_{4}$ $H_"2"SO_"4"$ is $0.3$ $0.3$ . This is a very small value, indicating its strong acidity.

Hope this helps :)

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How do you calculate the pH of a strong acid or base?

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