Mrs. Coyle Honors Chemistry Hydrates Mrs. Coyle Honors Chemistry

Hydrate: A crystalline compound in which the ions are attached to one or more water molecules.

Example: CuSO4•5H2O copper(II) sulfate pentahydrate

Prefixes for naming Hydrates mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10

Analyzing Hydrates Simulation click on the link below: http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/empirical.html

Problem 1: A sample of 0.235g of hydrated salt of cupric chloride is heated to 100oC. The mass of the sample remaining after heating is 0.185g. a) What percent by mass of the hydrate is water? b) How many moles of water are there for each mole of cupric chloride?

Problem 1 : Solution Mass of water in the sample = =0.235g -0.185g =0.050g % by mass water = =(0.050g/0.235g)x 100% =21.% by mass

Problem 1: Solution Cont’d b) Molar Mass of CuCl2 = Cu 63.546g +Cl 2(35.453g) 134.452g # mol CuCl2= 0.185g x 1mol 134.452g =1.38x10 -3mol CuCl2

Problem 1: Solution Cont’d Molar Mass H2O = H 2(1.008g) +O 15.994g 18.010 g # mol water= 0.050g x 1 mol = 18.010g =2.78 x10-3 mol water

Problem 1: Solution Cont’d # mol water = 2.78 x10-3 mol water = #mol cupric chloride 1.38x10 -3mol CuCl2 = 2.014 ≈ 2 1 1 So the formula of the hydrate is: CuCl2 ∙ 2 H2O