pH: 4.9 Calculate:

H3O
H30= 10^-pH
H3O=10^-4.9
H30=1.25 * 10^-4

AND CALCULATE

OH=14-pH
OH=14-4.9
OH= 9.1

1 answer

No. You must be pushing a wrong button. Hit the 10^x button, then -4.9 and read 1.256E-5M for H3O^+

For the second part, then
pOH = 14- pH = 9.1 (NOT OH = 14-pH) then
OH = 10^-pOH
OH = 7.94E-10