Question

1.Is there a difference between the freezing temperature and the melting temperature? Explain your respect in terms of numerical values, physical changes and changes in energy.

2.Suppose you have one mole of each of the following ionic solutes, NaNO3, CaCl2 and AIPO4, and that each of these dissolves in one kg of water. How many moles of particles will be in each of the solutions? Which of the solutions will have the lowest freezing point? and the lowest boiling point?

3. A solution of a non-ionic, non-volatile solute is prepared by dissolving 3,264g of this in 31.25mL of benzene. The resulting solution is frozen at 1.51 ° C Calculate the molar mass of the solute. (See Table 9.1 for benzene constants).

4.What advantage does the "coolant" (mixture of water and ethylene glycol) have over water?

Answer 1

2. Number of moles:

For NaNO_​​​3 2moles of particles will be there. 1for Na⁺ and 1 for NO_{​​​​3}^{​​​​-}​​​.

For CaCl2, 3 moles of particles will be there in the solution.

Similarly for AlPO4 2 moles of particles is present.

4. Water will freeze at it's freezing point which is O^{​​​​​​o}​​​​​C. For using water at temperatures around this there is always a rusk of the coolant solidifying.

But for a mixture of water and ethylene glycol depression in freezing point will occur so it can have freezing point below 0 ^o​​​​​​C. So it can be used in lower temperatures than water and it will not get solidified. And the coolant will continue to run and transfer the heat.