# Chemistry Question

Discussion in 'Community Discussion' started by jer446, Jan 9, 2006.

1. ### jer446 macrumors 6502a

Joined:
Dec 28, 2004
#1
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?

2. ### tweakers_suck macrumors regular

Joined:
Feb 7, 2005
Location:
Los Angeles, CA
#2
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.

### Staff Member

Joined:
Jan 20, 2005
#3
Hmmm...do you happen to have Mr. Tate at Highland High School in Salt Lake?

4. ### Phat_Pat macrumors 68000

Joined:
May 8, 2004
Location:
I Live Where I Live
#4
Suddenly the tread turns a creepy corner

5. ### jer446 thread starter macrumors 6502a

Joined:
Dec 28, 2004
#5
If this is right, i love you with all my heart.

Joined:
Dec 28, 2004

Joined:
Jan 20, 2005
#7
8. ### jer446 thread starter macrumors 6502a

Joined:
Dec 28, 2004
#8
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

9. ### aussie_geek macrumors 65816

Joined:
Apr 19, 2004
Location:
Sydney Australia
#9

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