Question

- UTUM IUIJ 1 SUIULIUIT, Lidl IS, I T ! 4. If 2.00 moles of a substance is dissolved in 1.00 kg of water, the freezing point of the solu- tion decreases by 7.44°C. Does this substance dissociate to form ions in solution? Explain why. 5. Calculate the freezing point of a 0.2 m CaCl, aqueous solution, assuming it dissociates completely to form ions in solution.

Answer 1

SOLUTION To find if the ons in solution substance will dissociate to form Given: No. of moles = 2.00 moles volume of solvent = 1.00 kg bob depression in freezing point = 7:44°c. 1 AT sixmxKp where AT = the change in the temperature i = the number of particles a substance will dissolve - into m . molality A o freezing point constant' 51.86 for water i molality = number of moles of solute dissolved of solvent = D i but the given values in equation 6 molality= 2.0 moles 2 mollkg, 281 1.0kg and substitutin i. Using the formula , AT =ixma Kf values - AT = ixmxxf. 7.44 °C = 10x12 mellkq) x(1086) Rearranging to wat get i i = 7.44€ 1 = 2. particlesi (amallkg.)x(1.86) .

So, the substance dissociates into 2 partide barticle in solution Explanation: Since it dissociates into a particles preferably cation and anion), it must be a compound. The dissociation is possible if the reaction is exothermi and feasible
An increase in entropy of a system leads to more feasibility of a process. Thus, a compound dissociates into particles or ions to increase the entropy of the system and increases stability.

The viability of a substance to form ions can be found by using a formula based ondepression in freezing point as shown in the images above.