11th gr. chem (composition of a hydrate)

[monica_e826]

i might get confusing cause i don't understand this very much
but here is the copy of my lab i need help with #1 & 6 of the POST-ALAYSIS
here is the word doc. of my lab
http://courses.digitaldapp.org/documents/Inquiry Lab - Experiment 03 - Composition of a Hydrate.doc


btw.
5 grams of copper II sulfate was used
when it became an anyhride it had a mass of 0.15g


i know i made a mistake somewhere in my lab and i was wondering if you tell where my mistake is and what i should do. i would highly appreciate it.

so i know...
CuSO₄ . 5H₂O
molar weight is 249.69g


by itself is
CuSO₄ = 159.61g
5H₂O= 90.81

so i took the
mass of the water/total mass of hydrate ^x100= 36% of H₂O removed in anhydrous copper (II) sulfate.

am i correct?
this is where i got confused...
-determine the # of moles of water present in each mole of hydrous copper (II) sulfate.
so what i did was:
5H₂O

H₁₀= 11%=11/1.0079=10.91=2
O₅=88%=88/15.9994=5.5=1
is this the correct Empirical formula?
2H₁₀O₅ & can be simplified to 2H₂O

so now what do i use to find the amount of moles of water present?

 

[chemisttree]

i might get confusing cause i don't understand this very much
but here is the copy of my lab i need help with #1 & 6 of the POST-ALAYSIS
here is the word doc. of my lab
http://courses.digitaldapp.org/documents/Inquiry Lab - Experiment 03 - Composition of a Hydrate.doc


btw.
5 grams of copper II sulfate was used
when it became an anyhride it had a mass of 0.15g

Are you sure you got that right? I assume that "it had a mass of..." means that the anhydride had a mass of... Is that right?

i know i made a mistake somewhere in my lab and i was wondering if you tell where my mistake is and what i should do. i would highly appreciate it.

so i know...
CuSO₄ . 5H₂O
molar weight is 249.69g


by itself is
CuSO₄ = 159.61g
5H₂O= 90.81

Good so far...

so i took the
mass of the water/total mass of hydrate ^x100= 36% of H₂O removed in anhydrous copper (II) sulfate.

am i correct?
this is where i got confused...
-determine the # of moles of water present in each mole of hydrous copper (II) sulfate.

Here is where you strayed off course. The formula for your unknown hydrate is CuSO₄ . XH₂O. You need to solve for 'X', not assume that it is 5 and do some math without using any of the data you collected.

Show us the raw data you collected.