Riley let his friend borrow $12,750. He wants to be paid back in 57 months and is going to charge his friend a 5.5% interest rate. How much interest will his friend have to pay?

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.