Measurements show that the ph of a particular lake is 4.0. what is the hydroxide ion concentration of the lake?

[OH⁻] → 1×10⁻¹⁰

Explanation:

pH = - log [H⁺]

pOH = - log [OH⁻]

pH + pOH = 14

4 + pOH = 14

14 - 4 = 10 → pOH

10^-pOH = [OH⁻]

10⁻¹⁰ = [OH⁻] → 1×10⁻¹⁰

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3