Physics, Chemistry and Biology: Post your doubts here!

[Iridescent]

can anyone send me some notes on acid bases and salts (Olevel,extended) plzzz...
i badly need this...

Check here, all the notes are available:
https://www.xtremepapers.com/community/threads/useful-stuff-compiled.10273/

 

[Kdown567]

17 Which change does not increase the speed of reaction between zinc and hydrochloric
acid?
A adding a catalyst
B decreasing the temperature
C decreasing the particle size of the zinc
D using more concentrated acid

Why is it B not C , from oct nov 09 CHEM paper /12

 

[Kdown567]

Its obvious. But slightly confusing....
Decreasing the particle size means increasing the surface area of the reactant..... use a bit of logic
and option B its self explanatory

Ah thank you , I thought C meant decrease in S.A.

 

[Counter Logic Gamer]

please help me understand


0625/11


Paper 1 Multiple Choice May/June 2009

Question 1,2,3
Explanation needed!!

 

[architnsk]

Guys i need help in chemical calculations, i often get confused and cannot decide when to take the ratios of moles and when the moles should be the same
I also have a doubt in in the oct/nov paper 2005 ques 7c,oct/nov 2008 ques 7a(i) and please send me a pdf file or notes for the same topic

 

[Francium98]

Chemistry: What does this mean: Describe evidence for the movement of particles in gases and liquids (a treatment of Brownian motion is not required) ??

 

[Counter Logic Gamer]

i dont understand about chemistry- electrolysis the anode changing acidic.Can anyone explain and give me notes about this??

 

[Counter Logic Gamer]

the solution becoming acidic near the anode ... and so one .

 

[Atiqa asl]

the solution becoming acidic near the anode ... and so one .

I really didn't understand ur question

 

[Counter Logic Gamer]

when copper sulphate is solution what happen is graphite is electrode ...??

 

[Atiqa asl]

if electrolysis then yes
if purification of impure cu then noo

 

[Counter Logic Gamer]

If graphite is the electrode then the products are :
Anode- oxygen why?? a bit more brief xplanation please tmrw s my chemistry xam !!
Cathode- Copper
Solution left in the beaker - sulphuric acid how??

 

[Counter Logic Gamer]

Aqueous sodium hydroxide is added to a solution of a salt. A blue precipitate is formed which
does not dissolve in excess.

Aluminium foil is added to the mixture and the mixture is warmed. A gas is produced that turns
damp red litmus paper blue.

What is the name of the salt?
A ammonium nitrate
B ammonium sulfate
C copper(II) nitrate
D copper(II) sulfate
Hows is the answer C. Explanation Needed!! Please

 

[Counter Logic Gamer]

An element E is burned in air. A white solid oxide is formed.

The oxide is tested with damp red litmus paper. The paper turns blue.

What is element E?
A calcium
B carbon
C iodine
D sulfur
Hows the answer A.Explanation Needed...Please

 

[Kdown567]

An element E is burned in air. A white solid oxide is formed.

The oxide is tested with damp red litmus paper. The paper turns blue.

What is element E?
A calcium
B carbon
C iodine
D sulfur
Hows the answer A.Explanation Needed...Please

Sulfur and carbon oxides such as sulfur dioxide and carbon dioxide are acidic and the litmus paper would not turn blue.
Iodine does not form a white solid oxide , and from lab experience we know that calcium oxide is white and since all metal oxides are basic (turn litmus blue) we can say the answer must be A calcium oxide as it is the only option that fits it

 

[SREYAh]

hey guys.. i want some notes on enzymes i just can't understand this chapter (for o level, extended)... please help me....i want some clear notes....can you give me please!!!

 

[Nabeel.Ahmad]

If graphite is the electrode then the products are :
Anode- oxygen
Cathode- Copper
Solution left in the beaker - sulphuric acid

But during the purification of copper, the cathode is made of pure copper and the anode is made of impure copper. So the products are:

Anode - the electrode gets smaller. But nothing is produced here
Cathode- the electrode gets bigger due to the accumulation of copper. Also no chemicals are released here. .

Solution in the beaker- the blue colored solution gets faded.

The blue colored solution does not fade. The electrolyte is also Copper Sulphate. The Anode provides Copper Ions, and they get deposited on the Cathode. For each Copper Ion that leaves the anode to come into the Electrolyte, one Copper Ion is deposited on the Cathode. So the Color of the Electrolyte does not change. It remains Blue.

 

[Nabeel.Ahmad]

Chemistry: What does this mean: Describe evidence for the movement of particles in gases and liquids (a treatment of Brownian motion is not required) ??

Diffusion of Perfume, or Food Scent is an example.

 

[SREYAh]

hey guys.. i want some notes on enzymes i just can't understand this chapter (for o level, extended)... please help me....i want some clear notes....can you give me please!!!

 

[suri003]

look at this relation ----> when we test for iodine or bromine ions we use silver nitrate
so make the inverse ((( to test for silver ions use iodine )))

wat abt hexane ..... wat is d test 4 tat