You see a group of small fuse holders on a d i n rail in an industrial control cabinet the fuse holders are in groups of 5 and are separated by a single terminal block what's connected to the terminal block A. the AC or DC power to the fuses
B. system ground
C. the power supply natural
D. a control signal

In pure water, the concentration of hydronium ions, or H⁺, will equal the concentration of hydroxide ions. That is [H⁺] = [OH⁻].

Remember that Kw = [H⁺][OH⁻] for water and if [H⁺] and [OH⁻] are both equal, we can easily solve for them by taking the square root of Kw.

[H⁺] = [OH⁻] = sqrt(1.47*10^-14) = 1.21*10^-7

The concentration of hydroxide ions at 30 degrees Celsius is 1.21*10^-7