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

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

To calculate the value of H3O (hydronium ion concentration) with a pH of 4.9, you can use the formula H3O = 10^(-pH). In this case, the pH is equal to 4.9, so H3O = 10^(-4.9). Evaluating this expression gives H3O = 1.25 * 10^(-4).

Similarly, to calculate the value of OH (hydroxide ion concentration), you can use the formula OH = 14 - pH. In this case, the pH is 4.9, so OH = 14 - 4.9 = 9.1.

So, the calculated values are:
H3O = 1.25 * 10^(-4)
OH = 9.1