Answer: A solution that is a 4 on the pH scale is a (a) weak acid.
The pH scale is a universal measure of how much acidic or basic any substance is. The scale of pH ranges from 0 to 14 with 7 in middle being neutral i.e. neither acidic nor basic. Substances with pH less than 7 are considered to be acidic and more than 7 are considered to be basic. Strong acids have pH less than weak acid while strong bases have higher pH than weak bases.
Substances or solutions that have pH 0-3 are highly acidic, 4-6 are weakly acidic and pH of 7 is neutral solution while pH of 8-11 are weakly basic and 12-14 are highly basic.
