Question

John gets sick from drinking all that water fast, but recovers. He goes to lab the next day and makes a 50 mM solution of NaCl. He believes this NaCl solution has the same osmotic strength as 50mM urea. Is his assumption correct? Please explain (no calculations are necessary but please explain).

Answer 1

The assumption is wrong because in solution NaCl will be completely dissociated into Na⁺ and Cl^- ions while Urea will not dissociate into ions. Thus both will have different vant Hoff factor, as a result, the osmotic strength will also vary.