there are no opposites, its a +/- scale....silly goose
**************2nd Opinion****************
pOH could be considered the opposite of pH.
Alkali is the opposite on the ph scale.
6.5 is considered to be a weak acid on the pH scale. 7 is considered neutral and a pH < 7 is considered an acid.
7
A pH of 7 is considered neutral.
Anything with a pH less than 7 is considered acidic. So a pH of 6.4 is only slightly acidic.
Alkalis (bases) react with acids to neutralize them, so in one sense, they can be considered as "opposite" of acids. Bases produce pH values >7 and acids produce pH values <7.
Alkali is the opposite on the ph scale.
6.5 is considered to be a weak acid on the pH scale. 7 is considered neutral and a pH < 7 is considered an acid.
An acid. pH of 7 is considered neutral & pH of 8-14 is considered basic.
If you mean base as in the opposite of acid, limestone is calcium carbonate. The pH of it is 9- any number higher than 7 is considered a base. Number lower than 7 are acid.
7