Answer:
Concentration of product at equilibrium ;
![[H^+]=0.0000229 M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D0.0000229%20M)
![[CN^-]=0.0000229 M](https://tex.z-dn.net/?f=%5BCN%5E-%5D%3D0.0000229%20M)
Explanation:

initially
0.85 M 0 0
(0.85-x)M x x
The equilibrium constant of reaction = 
The expression of an equilibrium cannot can be written as:
![K_c=\frac{[H^+][CN^-]}{[HCN]}](https://tex.z-dn.net/?f=K_c%3D%5Cfrac%7B%5BH%5E%2B%5D%5BCN%5E-%5D%7D%7B%5BHCN%5D%7D)

Solving for x:
x = 0.0000229
Concentration of product at equilibrium ;
![[H^+]=0.0000229 M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D0.0000229%20M)
![[CN^-]=0.0000229 M](https://tex.z-dn.net/?f=%5BCN%5E-%5D%3D0.0000229%20M)
The mass of water that will be needed to make the solution is calculated as below
% solution = mass of the solute/mass of the solvent(water) x100
% solution = 5% = 5/100
mass of the solute =0.377 g
mass of the solvent = ?
let the mass of the solvent be represented by Y
= 5/100 =0.377/y
by cross multiplication
5y= 37.7
divide both side by 5
y =7.54 grams
The part of the atom that takes up the most space is the amount of electrons
Moles of Zn: 26 / 65 = 0.4
Moles of S: 12.8 / 32 = 0.4
Molar ratio of Zn : S = 1 : 1
Empircal formula: ZnS
The answer is C