Biology; Chemistry; Physics: Post your doubts here!

[SalmanPakRocks]

 

[daredevil]

I think they have written wrong, there is no logic how 4 atoms became 2 ions.. :S

i double checked the ms ryt now
there are 2 equations for this reaction in it:
2H2O - 2e- --> 2H+ + O2
and the other one is:
2H2O --> 2H+ + O2 + 2e-

again in both the equations the H is not balancing out...!! :/

 

[ashiqbal]

2H2O --> 4H+(aq) + O2(g)
but in the marking scheme it is given:
2H2O --> 2H+ + O2 + 2e-

i just solved and ms is wrong
it has to be 4e- at the end!!

yes ms is wrong! it isnt like there are no mistakes in ms, i once read: potassium permanganate turns green! it was supposed to be colourless!!

 

[Spidey21]

Think time people!
Explain why all cell reactions are exhothermic and redox?(2)

If a solution contains dilute sulphuric acid and It has one ELECTRODE as Iron and Other ELECTRODE as Zinc! and Hydrogen gas evolves at Iron Electrode what would be the Anode? Give a reason for your choice(2)

2) anode would be the Zinc electrode cuz hydrogen being postive will emerge at Cathode

1) they give away energy so they are exothermic and redox reactions cuz one substance is oxidised while other is reduced!!

 

[Spidey21]

2H2O --> 4H+(aq) + O2(g)
but in the marking scheme it is given:
2H2O --> 2H+ + O2 + 2e-



yes ms is wrong! it isnt like there are no mistakes in ms, i once read: potassium permanganate turns green! it was supposed to be colourless!!

the day it does i will dance on Shahrah E faisal!!

 

[daredevil]

Think time people!
Explain why all cell reactions are exhothermic and redox?(2)

If a solution contains dilute sulphuric acid and It has one ELECTRODE as Iron and Other ELECTRODE as Zinc! and Hydrogen gas evolves at Iron Electrode what would be the Anode? Give a reason for your choice(2)

don't know about the first question exactly but for the second question is it simple cell or electrolytic?? if simple then the more reactive will b the anode (Zinc). is that ryt?

 

[MustafaMotani]

Think time people!
Explain why all cell reactions are exhothermic and redox?(2)

If a solution contains dilute sulphuric acid and It has one ELECTRODE as Iron and Other ELECTRODE as Zinc! and Hydrogen gas evolves at Iron Electrode what would be the Anode? Give a reason for your choice(2)

they are exothermic coz they increase surrounding temperature redox because oxidation takes place at negative electrode and redction at positive

Zinc is negative electrode because its more reactive so electrons flow from there to zinc and as Iron takes electrode its positive

 

[Spidey21]

View attachment 11501

C

 

[Dukeofwin]

Which of the following is correct about Ammonium Sulphte
1. Its gives of CO2 when heated with NaOH
2.It forms blue ppt when added to Barium Chloride
3.It can be made by adding sulphuric acid to ammonia
4.Farmers use it to make the soil alkaline.

P.S only one option is correct!

 

[ashiqbal]

View attachment 11501

It is Carboxylic acid
X is carbon so it is 4
Y is Oxygen so it is 6
Z, we dont have to even look at it!
so its C

 

[syed1995]

Idk... he said he will
hurry up syed1995 .... with that equation... plzz... meri light chali jaaye gi

2H2 + O2 ---> 2H2o that was the general equation ..

2H20 - 4e --> 4H+ + O2 ...

my bad .. didn't notice the 2h2 part .. lol

is that correct?

 

[MustafaMotani]

don't know about the first question exactly but for the second question is it simple cell or electrolytic?? if simple then the more reactive will b the anode (Zinc). is that ryt?

Zinc will be negative

 

[ashiqbal]

Which of the following is correct about Ammonium Sulphte
1. Its gives of CO2 when heated with NaOH
2.It forms blue ppt when added to Barium Chloride
3.It can be made by adding sulphuric acid to ammonia
4.Farmers use it to make the soil alkaline.

P.S only one option is correct!

C i think!

 

[syed1995]

Which of the following is correct about Ammonium Sulphte
1. Its gives of CO2 when heated with NaOH
2.It forms blue ppt when added to Barium Chloride
3.It can be made by adding sulphuric acid to ammonia
4.Farmers use it to make the soil alkaline.

P.S only one option is correct!

3

 

[ashiqbal]

2H20 - 2e --> 2H+ + O2 ...

is that correct?

Hydrogen doesnt balance!

 

[MustafaMotani]

2H20 - 2e --> 2H+ + O2 ...

is that correct?

LOL u copied from ms... we cant be fooled...

 

[Spidey21]

Which of the following is correct about Ammonium Sulphte
1. Its gives of CO2 when heated with NaOH
2.It forms blue ppt when added to Barium Chloride
3.It can be made by adding sulphuric acid to ammonia
4.Farmers use it to make the soil alkaline.

P.S only one option is correct!

3

 

[Dukeofwin]

Spidey21 and MustafaMotani Thanks, both are spot on!

 

[Spidey21]

Spidey21 and MustafaMotani Thanks, both are spot on!

like always
lol jk!!

 

[xxvvyy]

http://www.xtremepapers.com/papers/...al O Level/Chemistry (5070)/5070_w05_qp_2.pdf

question no 5/ a/ ii)