Why would a candle stop burning when oxygen concentration is at its lowest?

The candle will give out less light if there is a lower of oxygen. This happens because a high concentration of oxygen means that there are a of oxygen molecules near the wax. With a lot of molecules - it is likely that the molecules will bump into the wax.

:)

b is the correct

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.