Question

why we are not hurt by drinking cola soda or orange juice even though they both have an acidic pH

Answer 1

Our stomach is way acidic than these, I think our stomach has a pH of 1-2, so mere soda and oranges won't hurt at all :)

Answer 2

but, orange juice has a pH around 3 and cola around 2 .. ?

Answer 3

If you remember, oranges have high concentration of citric acid, its a weak acid. and soda drinks has pH around 2.5 according to http://quittingsoda.com/post/the-acidity-ph-of-soda-pop

Stomach acids are hydrochloric acids, which we all know is a strong acid :)

Answer 4

it makes sense now haha thaanks