2.1 billion years
2,139,000,000 to be exact
Synthesis. Which is "<span>Noun. (plural syntheses) The formation of something complex or coherent by combining simpler things. (chemistry) The reaction of elements or compounds to form more complex compounds.".....According to www.dictionary.com.</span>
By using the ICE table :
initial 0.2 M 0 0
change -X + X +X
Equ (0.2 -X) X X
when Ka = (X) (X) / (0.2-X)
so by substitution:
4.9x10^-10 = X^2 / (0.2-X) by solving this equation for X
∴X ≈ 10^-6
∴[HCN] = 10^-6
and PH = -㏒[H+]
= -㏒ 10^-6
= 6
This one is beta decay (the -1 subscript tells us that)