Biology; Chemistry; Physics: Post your doubts here!

[Suchal Riaz]

In a titration between an acid (in the burette) and an alkali, you may need to re-use the same
titration flask.
Which is the best procedure for rinsing the flask?
ARinse with distilled water and then with the alkali.
BRinse with tap water and then with distilled water.
CRinse with tap water and then with the acid.
DRinse with the alkali.
What is the correct option??

with tap water then with distilled water.
if u use alkali or acid, it will affect final result as alkali will increase concentration of alkali in next reaction and if u wash with acid some of acid will remain and it will react will alkali ths decreasing concentration of alkali even before u started titration.

 

[TheLeagueofShadows]

In a titration between an acid (in the burette) and an alkali, you may need to re-use the same
titration flask.
Which is the best procedure for rinsing the flask?
ARinse with distilled water and then with the alkali.
BRinse with tap water and then with distilled water.
CRinse with tap water and then with the acid.
DRinse with the alkali.
What is the correct option??

I think its C. First we have to rinse with water and then with the acid or alkali which was used before in the instrument.

 

[TheStallion-Reborn]

In exothermic, increasing the temperature decreases the forward reaction
In endothermic, increasing the temperature increases the forward reaction

any idea about WHY would that happen? i have a set of notes which mention le chatlier's prinicple, I however didn't get it. If you could please explain the reason behind it.

 

[Suchal Riaz]

I think its C. First we have to rinse with water and then with the acid or alkali which was used before in the instrument.

i guess u r doing chemistry for the first time. do u have any reason to support ur answer. read my response:

with tap water then with distilled water.
if u use alkali or acid, it will affect final result as alkali will increase concentration of alkali in next reaction and if u wash with acid some of acid will remain and it will react will alkali ths decreasing concentration of alkali even before u started titration.

 

[usama321]

yup i think it is C too.

 

[Suchal Riaz]

any idea about WHY would that happen? i have a set of notes which mention le chatlier's prinicple, I however didn't get it. If you could please explain the reason behind it.

if u increase temperature the speed will always increase but production depends.
if it is exothermic reaction then it prefers less heat as it producec head itself. but the backward reaction is endothermic which prefers more temperature. so u have created conditions which favours backward(endothermic) reaction so forward reaction(in this case exothermic) will obviously produce less.
opposite in the case of endothermic reaction as forwards as if u increase temperature it will produce more products as it needs heat to react and more heat means more production. thus forward reaction will be more than backward(exothermic)
increasing speed will always increase speed of both, but actually the speed of endothermic will be more than exothermic.

 

[ijlalm]

A certain quantity of electricity liberates 9 g of aluminium. The mass of copper liberated from copper(II) sulfate
solution (Cu2+
ions) by the same quantity of electricity is: (Relative atomic masses: Al = 27; Cu = 64)
A 9.0 g
B 21.33 g
C 32.0 g
D 42.67 g
E 64.0 g
Anyone.. Help please!!
Agar is ka ans kisi ko aagaya wo BAAP hai

 

[Suchal Riaz]

this will answer all ur questions zainabkhann
it has list of variable their symbol, tips for drawing graphs, for revision and much more.
i downloaded it from cambridge student site

 

[usama321]

i guess u r doing chemistry for the first time. do u have any reason to support ur answer. read my response:

cool down a bit my chemistry teacher told me too that the answer is C. lets first confirm it, ok?

 

[ijlalm]

cool down a bit my chemistry teacher told me too that the answer is C. lets first confirm it, ok?

But the marking scheme says that the ans is B

 

[usama321]

But the marking scheme says that the ans is B

ohkkkkk . hmmmm, what year is it?

 

[Suchal Riaz]

cool down a bit my chemistry teacher told me too that the answer is C. lets first confirm it, ok?

so please tell me why u need to rinse with acid/alkali? to get inaccurate results. if u reuse something u want it to be like new if u wash it. so if u wash it by acid/alkali then it will be like used one then what is purpose of rinsing? a new one will be neutral so make it neutral by washing it with water so all acid/alkali is washed away.

 

[Suchal Riaz]

ohkkkkk . hmmmm, what year is it?

u must have heard wrong from ur teacher

 

[ijlalm]

ohkkkkk . hmmmm, what year is it?

W11 question paper 11__5070 chemistry

 

[usama321]

so please tell me why u need to rinse with acid/alkali? to get inaccurate results. if u reuse something u want it to be like new if u wash it. so if u wash it by acid/alkali then it will be like used one then what is purpose of rinsing? a new one will be neutral so make it neutral by washing it with water so all acid/alkali is washed away.

hmmmm. Ok thanks for clearing it up . i might have gotten it wrong then . By the way, does anyone has a link to the mark scheme of paper 4 chemistry 2002?

 

[TheLeagueofShadows]

i guess u r doing chemistry for the first time. do u have any reason to support ur answer. read my response:

Keep guessing! . And try to keep the conversation polite. Btw, for washing out burette/ other instruments, which contained only acid/alkali but not both, we first have to wash by water and then by acid/alkali. You can see atp j 02 q9. But if we have both acid and alkali then we have to wash with water both times like you said.

 

[Suchal Riaz]

Keep guessing! . And try to keep the conversation polite. Btw, for washing out burette/ other instruments, which contained only acid/alkali but not both, we first have to wash by water and then by acid/alkali. You can see atp j 02 q9. But if we have both acid and alkali then we have to wash with water both times like you said.

there is no quesion like that in j 02 atp. and dont misguide others. there is no answer like that. classified answer is wrong. please add some prove or reason for ur answer
dont mind but this is how it is.

dont mind it please

 

[TheStallion-Reborn]

A certain quantity of electricity liberates 9 g of aluminium. The mass of copper liberated from copper(II) sulfate
solution (Cu2+
ions) by the same quantity of electricity is: (Relative atomic masses: Al = 27; Cu = 64)
A 9.0 g
B 21.33 g
C 32.0 g
D 42.67 g
E 64.0 g
Anyone.. Help please!!
Agar is ka ans kisi ko aagaya wo BAAP hai

year n paper?

 

[TheStallion-Reborn]

A certain quantity of electricity liberates 9 g of aluminium. The mass of copper liberated from copper(II) sulfate
solution (Cu2+
ions) by the same quantity of electricity is: (Relative atomic masses: Al = 27; Cu = 64)
A 9.0 g
B 21.33 g
C 32.0 g
D 42.67 g
E 64.0 g
Anyone.. Help please!!
Agar is ka ans kisi ko aagaya wo BAAP hai

is the answer B? if yes, then Im BAAP!

 

[TheStallion-Reborn]

Keep guessing! . And try to keep the conversation polite. Btw, for washing out burette/ other instruments, which contained only acid/alkali but not both, we first have to wash by water and then by acid/alkali. You can see atp j 02 q9. But if we have both acid and alkali then we have to wash with water both times like you said.

why would v wash it with acid/alkali??