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Chemistry Question

J

jer446

macrumors 6502a
Original poster
Dec 28, 2004
826
0
Hello, i know a wierd place to ask, but i am having trouble doing one of my chem honors problems for a lab, and since everyone here is smart, can anyone tell me what they would write? Ok the question is:

The following results were obtained when a solid was heated by three different pairs of students. In each case the students observed that when they began to heat the solid, drops of liquid formed on the sides of the test tube.

(chart)
Student No. / Mass Before Heating / Mass After Heating
1. / 1.48g / 1.26g
2. / 1.64g / 1.40g
3. / 2.08g / 1.78g

A) Could the solid be a hydrate? What is your evidence?
B) If the solid after heating has a molar mass of 208 g/mole and a formula of xy, what is the forumla of the hydrate?

Thanks for your help guys
 
jer446 said:
Hello, i know a wierd place to ask, but i am having trouble doing one of my chem honors problems for a lab, and since everyone here is smart, can anyone tell me what they would write? Ok the question is:

The following results were obtained when a solid was heated by three different pairs of students. In each case the students observed that when they began to heat the solid, drops of liquid formed on the sides of the test tube.

(chart)
Student No. / Mass Before Heating / Mass After Heating
1. / 1.48g / 1.26g
2. / 1.64g / 1.40g
3. / 2.08g / 1.78g

A) Could the solid be a hydrate? What is your evidence?
B) If the solid after heating has a molar mass of 208 g/mole and a formula of xy, what is the forumla of the hydrate?

Thanks for your help guys
Click to expand...

OK, it has been a while but I get a hydrate of 1 xy with 2 H20.

Using data from student no.1:

1.48 g - 1.26 g = 0.22 g water released upon heating.

0.22 g water x mol/18 g water = 0.0122 mol H20

1.26 g xy x mol/208 g xy = 0.00608 mol xy


Then,

0.0122 mol H20/0.00605 mol xy = approximately 2 mol H20:1 mol xy.


So you get xy * 2 H20 for the hydrate.
 
Hmmm...do you happen to have Mr. Tate at Highland High School in Salt Lake?
 
wow lol, my teacher must have gotten this lab from somehwere else then. We did this lab, but replaced the compound with sodium carbonate hydrate. To bad the answers werent included
 
WildCowboy said:
Google just pulls up the most amazing things. Scroll to the end of this document. (This is why I asked where you were...)

http://www.slc.k12.ut.us/staff/doutat/Labs/Lab2-Hydrate.pdf
Click to expand...


HAH!! I wish the internet was around when I was at school!!. jer446's question is a deadset carbon copy of that one from google.

I did notice one thing, the question from google has a typo. 20.8 g should be 2.08 g.


aussie_geek
 
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