chp 10 question below

Question

the pH of question below

1. [OH−][OH−]M_4 = 8.1×10⁻⁹ MM

Express your answer using two decimal places.

2. [OH−][OH−]M_1 = 2.2×10⁻⁷ MM

Express your answer using two decimal places.

Answer 1

[OH-] = 8.1x10^-9 M (I have no idea what the M_4 is supposed to mean)

pH + pOH = 14

pOH = -log [OH-] = -log 8.1x10-9

pOH = 8.09

pH = 14 - 8.09

pH = 5.91

[OH-] = 2.2x10^-7 M

pOH = 6.66

pH = 14 - 6.66

pH = 7.34