80 minutes because:
1600 -> 20mins -> 800
800 -> 20 mins -> 400
400 -> 20 mins -> 200
200 -> 20 mins -> 100
4*20 mins = 80 minutes
Osmolarity=osmole of the solute/litres of the solution
ionic equation for dissociation of CaCl2 is
CaCl2--->Ca2+ +2Cl-
total osmoles for reaction are 1(Ca2+) + 2(Cl-)= 3 osmoles
therefore
0.50 moles of CaCl2 x 3 osmoles/ 1mole of CaCl2 = 1.5osmoles
osmolarity=1.5 /1.0 L=1.5 osmol/l
Thomson used a beam of negatively charged particles. Using a beam of particles and detecting the scattering of the particles after they hit gold foil.