Instructions for the lab:
Safety:e dishes are VERY HOT; always handle them with tongs. DO NOT put hot dishes on a balance! do not put water in hot dish! . Wear goggles at all times.
Introduction: Find the % of water in the hydrates (2):
you can watch removing water from a hydrate in my class, or a more carefully done you tube video about removing water from hydrate
A hydrate is a chemical that has water molecules loosely bonded to it. The water molecules are not actually part of the formula, so the formula is written slightly differently. An example would be CaSO4 . 3H2O. This chemical would be called calcium sulfate trihydrate. When finding the mass of this chemical, you find the mass of the calcium sulfate and then add 3 times the mass of water to it. (40 + 32 + 4(16) + 3(18) = 190g/mol. You can find the % water by dividing the mass of the 3 waters (54) by the mass of the entire hydrate(190). This would be the actual % water. The water can easily be removed from a hydrate just by heating strongly in an evaporating dish. You will be weighing a hydrate and heating it to remove the water (now called "anhydrous salt") and weigh it again. You can now find the percent of the water that was in the hydrate. This is your experimental % water. ___________________________________________________________________________________
first hydrate - copper II sulfate penta hydrate
absent? get data from classmate or use the sample data in bold;
Data and results: Record your data on notebook paper; mass dish____35.50g, mass dish and hydrate______38.00g, mass dish and a.s. after heating 1_______ 37.60g, mass dish and a.s. after heating 2.(optional) ________ 37.10g
Calculations: show your work.
calculate : exp % water in hydrate (from data)______________ work:
The name of the blue hydrate is copper II sulfate pentahydrate . What is its formula?
_____________________________
calculate actual % water (from formula) ___________work:
calculate % error_________ work:
mass of anhydrous salt in dish after heating _______
moles of anhydrous salt ______ work:
mass of water evaporated ________
moles of water evaporated ______ work:
mole ratio of water to a.s. (round to whole number) ______
work:
Was mole ratio what was expected? ______ Why or why not? ________________________________________________
Conclusion:
everyone must have data, calculations and conclusions . Need help with calculations? See my video. with information from your table and everyone must fill in the form. What does ‘hydrate’ mean? Anhydrous? Why do more than one heating? Describe the color change. Why grind up the hydrate? Which heating do you use to get the mass of water? Why? What are mistakes that could easily be made on this lab? Why? What is a use of this hydrate in real life? Does it have a common name?
___________________________________________________________________________________
2nd hydrate - epsom salts
absent? get data from classmate or use this sample data : mass dish____35.50g, mass dish and hydrate______38.00g, mass dish and a.s. after heating 1_______ 37.10g, mass dish and a.s. after heating 2(optional). ________ 36.7g
calculate : exp % water in hydrate (from data)______________ work:
calculate actual % water (from formula) ___________work:
calculate % error_________ work:
You can look on the carton for name. It's name is magnesium sulfate heptahydrate
conclusion: Describe the color change for this hydrate. What are some uses of this hydrate in real life? Does it have a common name?
Find mole ratio of water to a.s. Is it as expected? Why or why not?
you can check class data when I make it available