What teacher do you have? The level of this is quite high and this is not trivial for high school chemistry.
| Quote: | Originally posted by Ashendale
Today I recieved a exercise page from my chemistry teacher to do at home.
Anyway, I'm not quite sure I have the right answers. Would you check them and tell where I am wrong (If I am)?
1. How to make Cu soluble compound without using acid?
2AgNO3 + Cu -> Cu(NO3)2 + 2Ag
CuO + SO3 -> CuSO4 |
First one looks quite good. The second one is questionable. SO3 is the anhydride of a strong acid.
| Quote: | 2. 6 test tubes contain KOH, CaO, ZnO, CaCl2, SiO2 and P4O10. By experiementing, make sure which test tube contains which chemical. You can use water,
dilute H2SO4 and universal indicator.
P4O10 + 6H2O -> 2H3PO4
H3PO4 + 3ZnO -> Zn3(PO4)2 + 3H2O
CaO + H2O -> Ca(OH)2 (Add universal indicator)
ZnO + H2SO4 -> ZnSO4 + H2O | ZnSO4 + KOH -> Zn(OH)2 + K2SO4 | Zn(OH)2 (temp)-> ZnO + H2O
CaCl2 + H2SO4 -> HCl + CaSO4 | CaSO4 (temp)-> CaO + SO3 | CaO + H2O -> Ca(OH)2
I wasn't really sure about how to prove SiO2...I was thinking about adding water and showing that it won't react..But then again, ZnO
doesn't react either. It won't dissolve too..Any ideas?
About KOH, I was thinking about adding water and showing it gets really hot. (If I remember correctly, making hydroxide solution is quite exothermic?)
|
Add water to all of the test tubes. Some solids do not dissolve, some dissolve. P4O10 can be selected as first. Acidic with universal pH indicator.
Now, only 5 tubes are left.
Add drops of the solutions or suspension to dilute H2SO4. Three of them give a white precipitate as final result.
The one, which initially is clear and gives a white precipitate with dilute H2SO4 is CaCl2.
Of the other two, which give a white precipitate or suspension, one is SiO2, the other is CaO. You can distinguish these by testing pH. The alkaline
one is the CaO.
Now only two test tubes are left. The clear one is KOH, the suspension is ZnO.
| Quote: | 3. You are given 4 solid chemicals: MgCl2, K2CO3, ZnS and CuSO4. You are also given universal indicator, filter paper, concentrated acids, alkalis
and water. How to identify each chemical using as few reagants as possible?
ZnS + 2HNO3 -> Zn(NO3)2 + H2S (I was thinking you can identify sulfide from H2S gas?)
CuSO4 + 2NaOH -> Na2SO4 + Cu(OH)2 | Cu(OH)2 (temp)->CuO + H2O (yay, black CuO)
K2CO3 (temp)-> K2O + CO2 K2O + H2O -> 2KOH (Aah, the magical universal indicator shows us it's a base)
For MgCl2 I have got no ideas. At first I was thinking about reacting with silver(I)nitrate, but then again, it would only prove it's a
chloride.. |
Add water to a small part of each of the solids. The one which becomes blue is CuSO4.
Add dilute HCl to part of the other three solids. Two of them will bubble. The one, which smells badly is ZnS, the other one is K2CO3. The remaining
one is MgCl2.
| Quote: | 4. You got 4 tes tubes with Na2SiO3, Na2S, Na2SO3 and Na2CO3. Using one reagant, make sure which test tube has which chemical in it.
Again, I've got no ideas. At first I thought about reacting with Lead nitrate to form insoluble salts..But teacher told that the person
identifying those chemicals should know the colour of the salt. Sitting there, I thought maybe hyrdochloric acid would do it. And it would, for Na2S
and Na2CO3. They both form gas. But the other's dont. So now I don't have ANY ideas. Sulphuric acid wouldn't work neither, as Na2SO4 is
soluble in water  And neither would nitric acid. I can't react it with a base,
because I can't think of any chemical that would be soluble when reacting with sodium salt and then form insoluble compound |
[Edited on 27-9-2005 by Ashendale]
[Edited on 27-9-2005 by Ashendale] |
