Question

A)How many moles of ions are present in an ideal solution that is produced by dissolving 17.4 g of Cu(NO₃)₂ in 410 g of water?

B)An 17.1 g of an unknown non-ionizing solute is added to 96.7 g of water. If the boiling point of the solution is 100.7, what is the molar mass of the solute?

Answer 1

For Part A:

msol = 17.4 + 410 = 427.4 g

MM = 63.55 + 14*2 + 6*16 = 187.55 g/mol

mol = 427.4 / 187.55 = 2.28 moles

Part B.

Use the following expression:

= Kb x m solute / MM * kg solvent

= 0.52 * 17.1 / MM * 0.0967

= 100.7 - 100 = 0.7

MM = 0.52 * 17.1 / 0.7 * 0.0967

MM = 131.36 g/mol

Hope this helps