Asolution has [oh−] = 4.0×10−8. what is the value of [h+] for the solution? answers

Answer is: the hydrogen ion concentration is 2,5·10⁻⁷ M.
[OH⁻] = 4,0·10⁻⁸ mol/L, equilibrium concentration of hydroxide anion.
[H⁺] is the concentration of hydrogen ions.
[OH⁻] · [H⁺] = 10⁻¹⁴ mol²/L², ionic product of water on room temperature.
[H⁺] = 10⁻¹⁴ mol²/L² ÷  4·10⁻⁸ mol/L.
[H⁺] = 2,5·10⁻⁷ mol/L = 0,00000025 mol/L.

Combustion is the act or process of burning. therefore, i believe the answer is  a: burning wood. 

Idont really know sorry