Asolution of carbon dioxide in water has a hydronium ion concentration of 2.0 x 10^−6m. what is the concentration of hydroxide ion at 25 °c?

[OH⁻] = 5x10⁻⁹ M

Explanation:

Kw = 1x10⁻¹⁴

[H₃O⁺] . [OH⁻] = Kw

2x10⁻⁶ . [OH⁻] = 1x10⁻¹⁴

[OH⁻] = 1x10⁻¹⁴ / 2x10⁻⁶ → 5x10⁻⁹

the answer would be b i believe

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.