IONIC HYDRATE
DATA SHEET
Formula of hydrated salt (with unknown water composition)
______________________• ? H2O
(All salts used in this experiment have an integer ratio of water to salt)
Mass of empty crucible (3 decimal places)
__________________
Mass of crucible + hydrated ionic salt (before heating)
__________________
Mass of hydrated salt (before heating)
__________________
Mass of crucible + salt after 1st heating
__________________
Mass of crucible + salt after 2nd heating
__________________
Mass of crucible + salt after 3rd heating (if necessary)
__________________
Mass of anhydrous salt remaining in the crucible
__________________
Formula weight of anhydrous salt in g/mol
____________________
No. of moles of anhydrous salt remaining in the crucible
__________________
Mass lost during heating (i.e. mass of water driven off)
__________________
Formula weight of H2O (in grams/mole)
__________________
Moles of water lost in the heating process
Calculate molar ratio of salt : water (non-integer ratio)
(i.e. 4.35 : 1 or 6.78 : 1, etc.
___________________
_______ : ___1___
Moles of Water : 1 mole of Salt
Empirical formula of the hydrated salt (nearest integer ratio)
___________• ____H2O
% water in the hydrated salt calculated from the empirical formula. (Above)
__________________
TA Initials and Date: ________________
CM131 Experiment 1 Post Lab Questions
1. A 5.000 g sample of hydrated barium hydroxide Ba(OH)2∙xH2O is heated in order to drive off the
water. After heating the sample weighs 2.716 grams. What is the formula for hydrated barium
hydroxide?
2. How many grams of water will be lost when 8.000 g of Al2(SO4)3. 18H2O is heated?
3. Hydrated cadmium (II) nitrate, Cd(NO3)2·xH2O, is 23.36% water by mass. Determine the empirical
formula for hydrated cadmium (II) nitrate.
4. A student has been tasked to determine the percent water in calcium sulfate, CaSO4∙xH2O using the
procedure followed in this experiment. The student was not careful and did not follow the procedure
carefully. How would each of the errors below affect the calculated amount of water (“x”) determined
by the experiment? Would the determination of the amount of water (“x”) be incorrectly high or low?
You must explain your reasoning in order to receive credit.
a) The sample was heated too strongly, resulting in the formation of SO2 (g).
b) The student did not weigh the sample immediately after cooling. Instead, they left the sample
on the benchtop in the open air overnight, allowing the sample to absorb moisture from the
air before measuring its final mass.
5. Methane clathrate also called methane hydrate is a form of ice in which methane gas has been
trapped inside the crystal structure. Methane hydrate has the formula 4CH4·23H2O. Large quantities
of methane hydrate have been discovered in ocean sediments around the world. Mining these
deposits to obtain methane (i.e. natural gas) has been discussed for years. Determine the percent
water in methane hydrate. How many liters of methane gas at 1 atm pressure 20˚C could be
recovered from 1 metric ton (1000 kg) ? [Methane gas density = 0.667 g/L at 1 atm and 20˚C