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
The number of hydrogen atoms that are in 4.40 mol of ammonium sulfide is 2.12 x10^25 atoms
calculation
find the number of moles of Hydrogen in ammonium sulfide (NH4)2S
that is 4.40 x number of hydrogen atoms in (NH4)2S ( 4x2= 8 atoms)
moles is therefore= 4.40 x8= 35.2 moles
by use of Avogadro's law constant
that is 1mole = 6.02 x10^23 atoms
35.2 moles=?
by cross multiplication
{35.2 moles x 6.02 x10^23} /1 mole = 2.12 x10^25 atoms
