Red blood cells are isotonic with a solution having a total particle concentration of $0.30 mol L^{- 1}$ . A sample of cells is placed in $0.10 M$ $CaCl X_{2}$ solution at body temperature (assume $CaCl X_{2}$ dissociates completely). The cells will

Answer: D

CaCl X_{2} \to Ca X^{2 +} + 2 Cl X^{-}

gives

3 \times 0.10 = 0.30 mol L^{- 1}

of particles. This equals the particle concentration inside the cells, so the solution is isotonic and there is no net flow of water.