Chemistry help.
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Q1.
When testing for the nitrate ions, one is required to put in the sodium hydroxide followed by the aluminium foil.
wad is the porpose of the NaOh and Al foil? And why the NaOh muz be put first instead of Al foil?
Q2.
when testing for Cl ions..one is required to put in nitrate acid followed by lead OR silver nitrate. wad is the purpose of the 2 reagents? Can one put in Hcl acid instead of Nitrate acid?
help is appereciated. -
A1. Nitrate ion (oxidation state +5) is reduced to ammonium ion(oxidation state +3) by the metal added.(Metals are good reducing agent.)
Equation. NO3- -------> NH4+
Ammonium ions is then react with hydroxide ion (in NaOH) to produce ammonia gas
Equation. NH4+ + OH -------> NH3(g) + H2O(l)
Ammonia gas is the only common gas that is alkaline. Hence, red litmus paper turns blue.
A2. The purpose of adding nitric acid is to acidified the solution. Whereas the purpose of adding silver nitrate or lead nitrate is to show the result of precipitation.
AgNO3 + Cl ion -------> AgCl (White ppt. formed.)
Pb(NO3)2 + 2Cl ion -------> PbCl2 (white ppt. formed.)
However I am not so sure wheather the acidifying regent can be change or not but from my experience it couldn't be change. Say you want to find out Cl ion, you CANNOT use a regent containing the same ion, in this case HCl.
My 2 cent worth. -
as above
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common ion effect? damn..need to revise chem liaoOriginally posted by Darkness_hacker99:A1. Nitrate ion (oxidation state +5) is reduced to ammonium ion(oxidation state +3) by the metal added.(Metals are good reducing agent.)
Equation. NO3- -------> NH4+
Ammonium ions is then react with hydroxide ion (in NaOH) to produce ammonia gas
Equation. NH4+ + OH -------> NH3(g) + H2O(l)
Ammonia gas is the only common gas that is alkaline. Hence, red litmus paper turns blue.
A2. The purpose of adding nitric acid is to acidified the solution. Whereas the purpose of adding silver nitrate or lead nitrate is to show the result of precipitation.
AgNO3 + Cl ion -------> AgCl (White ppt. formed.)
Pb(NO3)2 + 2Cl ion -------> PbCl2 (white ppt. formed.)
However I am not so sure wheather the acidifying regent can be change or not but from my experience it couldn't be change. Say you want to find out Cl ion, you CANNOT use a regent containing the same ion, in this case HCl.
My 2 cent worth.
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Can't remember exactly for Q1, the purpose of adding NaOH is start a reaction (can't remember why this part was done, could be wrong). Adding the aluminum foil is to produce the ammonia gas, which will show the presence of nitrate ions.
For Q2, darkness_hacker explained liao.
You can't use HCl as the acidifying agent, because it will contain chloride ions. This will defeat the purpose of the experiment, because no matter how you test, chloride ions will be present due to HCl.
By the way, it is called nitric acid, not nitrate acid. Nitrate is the spelling for ions, in this case, silver nitrate or lead nitrate. -
all so pro.
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nx time...
http://beta.exactseek.com/exact/seek/search?catid=284&cached=www.chemicalforums.com/
One of the mods there is an sgfer too. -
so pro
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i flunked my chemistry..
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Originally posted by Darkness_hacker99:
but then ar..the metals does not contains H+ ions , the y the product of No3- has 4 H+ ions ?
A1. Nitrate ion (oxidation state +5) is reduced to ammonium ion(oxidation state +3) by the metal added.(Metals are good reducing agent.)
[b]Equation. NO3- -------> NH4+
Ammonium ions is then react with hydroxide ion (in NaOH) to produce ammonia gas
Equation. NH4+ + OH -------> NH3(g) + H2O(l)
Ammonia gas is the only common gas that is alkaline. Hence, red litmus paper turns blue.
A2. The purpose of adding nitric acid is to acidified the solution. Whereas the purpose of adding silver nitrate or lead nitrate is to show the result of precipitation.
AgNO3 + Cl ion -------> AgCl (White ppt. formed.)
Pb(NO3)2 + 2Cl ion -------> PbCl2 (white ppt. formed.)
However I am not so sure wheather the acidifying regent can be change or not but from my experience it couldn't be change. Say you want to find out Cl ion, you CANNOT use a regent containing the same ion, in this case HCl.
My 2 cent worth.[/b]
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u ask me is ask kerrect person liao.
me is a chemist by profession.
but hey sollie, me charge! -
cheem
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Missqi mei mei, did you make black gunpowder yet?Originally posted by missqi:nx time...
http://beta.exactseek.com/exact/seek/search?catid=284&cached=www.chemicalforums.com/
One of the mods there is an sgfer too. -
Teacher cover oxidation and reduction already?Originally posted by Classyfied:but then ar..the metals does not contains H+ ions , the y the product of No3- has 4 H+ ions ?
If yes, revise this chapter...
Note this point: Reduction is the gain of hydrogen.