How do you determine percent composition of a mixture of sugar and salt using conductivity?
The conductivity of a solution is proportional to the number of ions it contains. Sodium chloride (table salt) ionizes in water and sugar does not. If you have a conductivity meter you can find the conductivity of the solution, use that to determine the amount of salt present, and the rest will be sugar.
You will need to know:
- the mass of the undissolved mixture
- the volume of the solution
- the conductivity of the solution
- the molar conductivity of sodium chloride, calculated below:
Molar conductivity of NaCl=(molar conductivity of Na+)+(molar conductivity of Cl-)
since there's a 1: ratio of Na+ to Cl-,
molar conductivity= (0.05011)+(0.07635) = 0.12646 S x L x mol-1
S is Siemens, which is the inverse of Ohms.
0.12646 x molarity of ions = conductivity measured,
so molarity = conductivity/(0.12646)
(molarity of ions)(liters of solution) = moles of NaCl
Moles of NaCl x 58.5g/mol
= grams NaCl
(grams NaCl)/mass of mixture x 100% = % NaCl
100-%NaCl = % sucrose (sugar)