How about plants? in what way do they produce their food?

Photosynthesis

Explanation: it uses the sun to create food for themselves.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

fe 55.85 g/mol and h2o 18.02 g/mol.