Hydrate Lab
___________________Name
Purpose: To find the Empirical Formula of an unknown hydrate AB*H2O
Procedure/Data:
1.
2.
3.
4.
5.
Weigh a dry Crucible and lid ______________________
Weigh a crucible, lid and hydrate (1/3 full) _______________
Heat the hydrate with a Bunsen burner until the hydrate has completely changed colour
Cool the crucible, weigh the crucible, lid and anhydrate__________________
Remove the anhydrate from the crucible onto a paper towel and add water, record you
observations:
6. The formation of the anhydrate is a decomposition reaction, the formation of the hydrate is a
synthesis reaction, write a reversible reaction (using  ) showing the energy as a reactant or
product.
7. Discard the anydrate and wash and return the crucible and lid.
Calculations:
1.
Calculate the mass of the hydrate used:
2. Calculate the mass of the anydrate used:
3. Calculate the moles of anhydrate using the answer to Q2 and the molar mass provided by the
teacher.
4. Calculate the mass of the water removed while heating using the answers to Q1 and 2.
5. Calculate the moles of water removed.
6. Calculate the number of moles of water divided by the number of moles of the anhydrate,
round this to the nearest whole number.
7. The empirical formula is AB* ________H2O (put answer to Q6 in the blank)
Follow up Questions:
1. A 15.67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the
carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the
hydrate?
2. A substance was found to have the following percentages by mass: 23.0% zinc; 11.0% sulfur;
22.0% oxygen; 44.0% water. What is the empirical formula?