If you have any question on chem p6 im ready you guys. Don't Worry!!

[JimmyCarter]

I'mna answer any questions you have. I love chemistry and particularly paper 6

 

[Sajal mehta]

please explain the "preparing soluble salt" and which acid and base to chose

 

[JimmyCarter]

please explain the "preparing soluble salt" and which acid and base to chose

sorry for being late.
1st you choose an acid (sulfuric for sulfates, hydrochloric for chlorides, nitric for nitrates, and phosphoric for phosphates).
Choose a reactant. either a soluble reactant of an insoluble one. Soluble reactants are like Alkalis, ok? Insoluble reactant like Metals (MAZIT METALS, mg, al, zn, and sn) or a carbonate, or an insoluble base. Now if you choose a soluble reactant then you carry out titration, if you choose an insoluble reactant then you add an excess of this insoluble to the acid and filter and crystalize.
Soluble(acid) + soluble reactant= insoluble salt (percipitation)
Insoluble+Soluble= Soluble salt.

 

[Sajal mehta]

isnt it
1) Solid base (or metal) and an acid to make a SOLUBLE salt.
2) Soluble base (alkali) and an acid to make a SOLUBLE salt.
3) Precipitation method to make an INSOLUBLE salt.

 

[MERIHAN]

plz help me in this question :
how will we know when to use burette or measuring cylinder ??? is there any range of volumes for which we should use burette or measuring cylinder....
thnx in advance

 

[JimmyCarter]

Hi.

plz help me in this question :
how will we know when to use burette or measuring cylinder ??? is there any range of volumes for which we should use burette or measuring cylinder....
thnx in advance

when in a question they use a measuring cylinder and then later on they ask you how to make the experiment more accurate you say use a burette instead of a measuring cylinder because it is more accurate. I dont think theres a defined range of volumes, u dont need to know that
(pipette holds exactly 25cm cubed)

 

[JimmyCarter]

isnt it
1) Solid base (or metal) and an acid to make a SOLUBLE salt.
2) Soluble base (alkali) and an acid to make a SOLUBLE salt.
3) Precipitation method to make an INSOLUBLE salt.

Oh sorry sorry soluble plus soluble make a soluble. my bad

 

[Lost_Life]

could you give me some tips like on how to know something like the solvent used in chromatography
or what do we conclude from a test of ion
or where do we place fire?

 

[Lost_Life]

isnt burette and pipette very accurate?

 

[jaida al hinai]

a burette will allow u 2 dispense larger volumes than pipette & measuring cylinder can dispense larger volumes than burette & pipette

 

[JimmyCarter]

could you give me some tips like on how to know something like the solvent used in chromatography
or what do we conclude from a test of ion
or where do we place fire?

alright
they dont usually ask about that :S but you can always use water as a solvent. (but when to grind for example leaves to do chromatography to them, grind with ethanol bcuz chlorophyl dissolves in ethnol)

if like they say solid X was tested with NaOH(aq) and it gave a dirty green ppt then the conclusion is it contains Iron(ii). if it has pH of 1-2 it is a strong acid, 3-6 weak acid and so on.

they usually ask where heat is applied and it is under the substance to be decomposed. if like theres a wool with ethanol soaked in it, heat is applied in the wool.

 

[JimmyCarter]

yes they are more accurate than measuring cylinders

isnt burette and pipette very accurate?

 

[Lost_Life]

OKAY THEN, when do we know if their is no change in the test of ions

 

[Lost_Life]

I REALLY NEED HELP WHEN THEY ASK US TO CONCLUDE ABOUT TEST OF IONS!!!

 

[JimmyCarter]

If for example they say they added hydrochloric acid to Barium Chloride and they want the observation, then there is no change because HCl and BaCl2 do not react together. Also use the displacement rules. Like Cu cannot react with HCl because Cu is less reactive than the H+ ion and so would not displace it. ( Basic oxides do not dissolve in bases they only dissolve in acids, and acidic oxides only dissolve in bases and not acids)

OKAY THEN, when do we know if their is no change in the test of ions

 

[jaida al hinai]

could you give me some tips like on how to know something like the solvent used in chromatography
or what do we conclude from a test of ion
or where do we place fire?

do u mean hw 2 place the chromatography paper in a solvent or hw 2 calc. the Rf solvent front??

 

[JimmyCarter]

I REALLY NEED HELP WHEN THEY ASK US TO CONCLUDE ABOUT TEST OF IONS!!!

Lost life, actually YOU CAN!! if you memorize the test of cations and anions pretty well then conclusions become easy. Example, you know that Cu ions dissolve in excess ammonia to give a deep blue solution and that carbonates react with acids to give CO2 as an effervesence, and they ask you a substance was tested with Ammonia excess and gave a adeep blue solution and with acids it gave a gas that turns lime water milky(CO2) then this for sure contains a copper ion and a carbonate ion and so would be Copper Carbonate.

 

[Lost_Life]

If for example they say they added hydrochloric acid to Barium Chloride and they want the observation, then there is no change because HCl and BaCl2 do not react together. Also use the displacement rules. Like Cu cannot react with HCl because Cu is less reactive than the H+ ion and so would not displace it. ( Basic oxides do not dissolve in bases they only dissolve in acids, and acidic oxides only dissolve in bases and not acids)

I THUGHT that for example if, they mentioned, that the solution was added to hydrochloric acid,then it was added to barium chloride,
i thought that there is no product with such reaction...
is that right to?

 

[JimmyCarter]

I THUGHT that for example if, they mentioned, that the solution was added to hydrochloric acid,then it was added to barium chloride,
i thought that there is no product with such reaction...
is that right to?

yes its correct

 

[Lost_Life]

do u mean hw 2 place the chromatography paper in a solvent or hw 2 calc. the Rf solvent front??

no , a paper had a question saying suggest a suitable solvent for water-soluble fruit coloring's... i put ethanol,, but the answer is water