Chemistry - May 2007

After the separation of the precipitates NiS and CoS, the solution containing the other grp III cations were treated with 4M HNO3 & the solution was evaporated to a moist residue. Then the residue were dissolved with 1ml of water & the solution was transfered to a test tube. 4M NaOH were added until precipitate appeared, then 10 drops of 4M NaOH were added in excess. 6 drops of 3% H2O2 were added, then the solution was heated in a hot water bath for 5 min. The mixture was then separated: the residue washed with 10 drops water to which has been added 1drop of 4M NaOH & the centrifugate reserved for succeeding cation tests. The residue were then treated with 1mL of 4M HNO3 & 2drops 1 NaNO2. The mixture was stirred & heated in a water bath. The residue was separated from the solution & discarded.
questions:
(1) what is the reason for the addition of "4M HNO3 & evaporation of the solution to a moist residue"?
(2) why add excess NaOH?
(3) What is the residue discarded in the last part?

2007-05-15 04:59:18 · 2 answers · asked by piangpiang 2

Label on a gallon of orange juice says 100% vitamin C but according to science, pasteurzation { Heating) destroys vitanim C.

2007-05-15 04:45:03 · 2 answers · asked by genebean 1

2007-05-15 04:43:43 · 2 answers · asked by Anonymous

If the volume of a gas container at 32.0deg. C changes from 1.55 L to 755mL, what will hte final temp be?

I came up with...1.55/305=0.775/T = 152.5K which is equal to 425.5C. I sure I am wrong but can anyone help?

2007-05-15 04:33:16 · 8 answers · asked by Anonymous

2007-05-15 04:25:02 · 1 answers · asked by britt77016 1

2007-05-15 03:50:30 · 6 answers · asked by Prats 1

Any substrate except Gold

2007-05-15 03:25:46 · 1 answers · asked by Anonymous

1)isobutyl bromide
2)isobutyl alcohol
3)t-butyl alcohol
4)isobutyl methyl ether
5)2,2,3,3-tetramethylbutane
6)2-methylpropene

2007-05-15 03:11:45 · 1 answers · asked by Sean L 1

Need help with this one...
The components of a firecracker are sulfur, powdered elemental aluminum, and potassium perchlorate. When the mixture is ignited, the following occurs:

S8(s) + 8A1(s) + 7KCIO4(s) --> 4A12O3(s) + 7KC1(s) + 8SO2(g)

What is the oxidizing agent, the reducing agent, the substance oxidized, and the substance reduced during the reaction?

2007-05-15 03:09:09 · 2 answers · asked by Anonymous

2007-05-15 01:48:49 · 5 answers · asked by princy 1

I'm doing a 3rd yr secondary school Forensic Science Assignment, and have to compose a murder story. I need the name of a poison as described. The murderer isn't me, duh :P

2007-05-15 01:39:34 · 5 answers · asked by Naahmah 2

I have a project I am doing and I could not find very many.

2007-05-15 01:12:59 · 5 answers · asked by ShellBell 1

A solution was made from 4.77g NaCl and 27.90g H2O. Calculate the mole fraction of NaCl in the solution.

0.0551
0.0451
0.0501
0.146
0.131
0.161

2007-05-15 00:43:13 · 3 answers · asked by Anonymous

2007-05-15 00:36:14 · 1 answers · asked by Anonymous

Explain how the attraction that the nucleus exerts on an electron changes with the principal energy of the electron.

2007-05-14 23:14:01 · 1 answers · asked by love2nnelly 1

when u do an acid base titration, does the solution with the unkown concentration go in the pippette or burette? please help..i have an exam 2mrw...thanks

2007-05-14 21:25:26 · 5 answers · asked by Anonymous

which of the solutions would be considered unsaturated?
a) dissolve 1.85 moles of NaCl in 300 ml of water
b) dissolve 5.8 moles of NaCl in 1 L of water
c) dissolve 3.25 moles of NaCl in 500 ml of water
d) none of these

2007-05-14 20:43:27 · 3 answers · asked by Anonymous

IF you added heat to the product side which way would it go or if you took out heat which way would it go. Basically it's confusing to me the factor of heat and it's impact on an equilibrium expression.

2007-05-14 19:39:32 · 2 answers · asked by Bri 3

can someone tell me a easy recipe for making soap at home using easily available and cheap products?and please tell the chemical activities of a soap.please do help me it is a part of my chemistry project. i need the ingredients as well as the process along with a list of its chemical reactions and activities.

2007-05-14 19:30:44 · 6 answers · asked by magnum 2

2007-05-14 19:27:34 · 3 answers · asked by Bri 3

is the mole ration of EDTA:Ca equal to 1:1? i think that all metal ions, irrespective of valence form 1:1 complexes with EDTA, is this right?

the only equation i have to work from is
MgY^2- + Ca^2+ --> Mg ^2+ CaY^2-

not sure.....

2007-05-14 18:37:11 · 1 answers · asked by Anonymous

a) its [H3O+} is 1.0 x 10^5 M
b) its [H3O+] is 1.0 X 10^-5 M
c) its [H3O+] is 1.0 x 10^9 M
d) it is more acidic than a solution whose pH is 4.00
e) none of the above

2007-05-14 18:30:24 · 3 answers · asked by Anonymous

I titrated acetic acid with NaOH and have the volume and concentration of NaOH and need to solve for the concentration of acetic acid.. what formula I should use? Is it M1V1=M2V2?

2007-05-14 18:21:30 · 2 answers · asked by Anonymous

2007-05-14 18:06:00 · 1 answers · asked by elakerfan2002 1

+2Kl(aq)>>>>PbI2(s)+2KNO3(aq)

2007-05-14 17:31:24 · 1 answers · asked by Anonymous

im trying to make a couple of smoke bombs using this site

http://chemistry.about.com/od/demonstrationsexperiments/ss/smokebomb.htm

on that page it says that i need potassium nitrate (KNO3), also known as saltpeter. well i cant get it, nor find it, so is it possible to find a fertalizer that has the chemical in it and crush it and use that instead of the pure form?

please i dont need any posts saying "this is extremely dangerous and dont do it!" i KNOW that. all im asking is would that work?

2007-05-14 17:02:54 · 1 answers · asked by Tyler 1

-californium
-europium
-cerium
-nobelium

2007-05-14 16:58:21 · 3 answers · asked by dzyldarchitects 2

i dont get why Ag2CrO4 is not Silver (IIII) Chromate and why its silver chromate

2007-05-14 16:26:02 · 5 answers · asked by ursportsguy 1

The atomic number of fluorine-19 is_______.
Its mass number is_______.
The shorthand notation for fluorine-19 is: ----
F
----

is your answer reasonable? why?

2007-05-14 16:21:31 · 3 answers · asked by Anonymous

How many grams of bromine are in 1.57 grams of phosphorus tribomide?

and

Calculate the mass percent oxygen in magnesium nitrate.

Thankyou!!

2007-05-14 16:13:13 · 1 answers · asked by Anonymous