General Chemistry Acid$-$Base Review

Biochemistry is exclusively water$-$based chemistry

Strong acids and strong bases ionize completely in water

Weak acids and weak bases don't completely ionize in water

Acidity of a solution is measured in terms of $pH$

The p means $"-$log$",$ so $pH$ means $-log[H^{+}]$

The $pH$ scale usually is $0-14,$ with $7$ being neutral, but goes below $0$ and above $14$ if a solution is more concentrated than $1M.$

@ Questions:

What is the $pH$ of a solution of $HCl$ that is $0\mathrm{.}75M?$

What is the $pH$ of a solution of $HCl$ that is $12M?$

What is the acid concentration of a solution of a strong acid that is $pH=3?$

Water ionizes naturally as follows:

$H_{2}O{H}^{+}+O{H}^{-}$

The amount of that ionization is shown with:

$K_w=[H^{+}][O{H}^{-}]=1\mathrm{.}0{10}^{-14}$

When we take $-$log to both sides of this...

$-log[H^{+}][O{H}^{-}]=-log[1\mathrm{.}0x{10}^{-14}]$

Remembering our precalculus log properties, where log $[$a$][b]=log[a]+log[b]dots$

$-log[H^{+}]+-log[O{H}^{-}]=-log[1\mathrm{.}0x{10}^{-14}]$

This is simplified to:

$pH+$pOH$=14$

We don't really measure this with pOH paper or pOH probes, but it is useful if you have the $pH$ of a hydroxide solution, you can find the concentration of hydroxide using this.

$$ Questions:

The $pH$ of a hydroxide solution is $8\mathrm{.}0.$ What is the pOH $?$

What is the $O{H}^{-}$in that solution?

What is the $O{H}^{-}$in an $HCl$ solution with a $pH$ of $6\mathrm{.}5?$