Biology; Chemistry; Physics: Post your doubts here!

[TheStallion-Reborn]

Yes and ammonium carbonate.

but i supose all v have to worry about (4 o levels is) the molten part is very easy positive ions go towards the cathose n negativ towards anode as fr aqueous, its oxygen everytym xcpt fr when it is chlorine, bromine or iodine in CONCENTRATED form...as for cathode, if the positive ions are above hydrogen in reactivity series thn hydrogen is discharged n if below hydrogen (copper n silver) thn the metal is discharged. m i write ? :-/ please correct me if im wrong

 

[asma tareen]

well i dunno abt it i jxt wanted to knw abt carbonates

 

[TheStallion-Reborn]

oh. n theres another dumb question. N this seriously has started pissing me off! GOD iv got no tym left n im cuming up wid such problems. aniways, ur valuable help is needed here.
http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s06_qp_4.pdf question 7 & 9(a)

 

[Saad Mughal]

but i supose all v have to worry about (4 o levels is) the molten part is very easy positive ions go towards the cathose n negativ towards anode as fr aqueous, its oxygen everytym xcpt fr when it is chlorine, bromine or iodine in CONCENTRATED form...as for cathode, if the positive ions are above hydrogen in reactivity series thn hydrogen is discharged n if below hydrogen (copper n silver) thn the metal is discharged. m i write ? :-/ please correct me if im wrong

You nailed it!
Yeah, we only need to know about molten and aqueous solutions and about bromine, iodide, chloride, hydroxide, nitrate and sulphate and how concentration affects them but there is no harm in learning more is there?

 

[asma tareen]

i think fr q7 its redox

oh. n theres another dumb question. N this seriously has started pissing me off! GOD iv got no tym left n im cuming up wid such problems. aniways, ur valuable help is needed here.
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s06_qp_4.pdf question 7 & 9(a)

7

 

[Saad Mughal]

oh. n theres another dumb question. N this seriously has started pissing me off! GOD iv got no tym left n im cuming up wid such problems. aniways, ur valuable help is needed here.
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s06_qp_4.pdf question 7 & 9(a)

For 7, it's (d) Redox, since the zinc replaces the copper (II) sulphate (since it is more reactive) and reduces it whereas the zinc itself gets oxidized and hence a redox reaction.
For 9, well iron (III) is the highest oxidation that an iron element can reach so potassium manganate (VII) cannot further oxidize it and hence won't react with it.
Hope that helps

 

[asma tareen]

and fr 9 a i guess it is already in its oxidized form and can not be further oxidised and KMnO4 is an oxidising agent so it cant react with it

 

[asma tareen]

yay my ans is correct

 

[Saad Mughal]

well i dunno abt it i jxt wanted to knw abt carbonates

Knowing about carbonates is not part of the syllabus but..
SO4 2-
NO3 -
CO3 2-
OH-
Cl -
Br -
I -
Here is the list.
Iodide ions are most readily discharged whereas sulphate and nitrate are not easily discharged.
Besides, in any event if nitrate, sulphate or carbonate is present then hydroxide (oxygen gas) will be discharged at anode.
Hope you get it

 

[TheStallion-Reborn]

For 7, it's (d) Redox, since the zinc replaces the copper (II) sulphate (since it is more reactive) and reduces it whereas the zinc itself gets oxidized and hence a redox reaction.
For 9, well iron (III) is the highest oxidation that an iron element can reach so potassium manganate (VII) cannot further oxidize it and hence won't react with it.
Hope that helps

i was finding 'displacement reaction' in the options. i get the point tht y is it redox. so should i consider it a rule tht displacement reactions are redox reactions? does this apply everywhere?
aaaaaaaa.......okay i get it...the prblem is,,,u cn never learn to answr such questions. i did have all the knowledge required in this question yet was cluless....It helpd alot! thankyouuuuu!!

 

[asma tareen]

Knowing about carbonates is not part of the syllabus but..
SO4 2-
NO3 -
CO3 2-
OH-
Cl -
Br -
I -
Here is the list.
Iodide ions are most readily discharged whereas sulphate and nitrate are not easily discharged.
Besides, in any event if nitrate, sulphate or carbonate is present then hydroxide (oxygen gas) will be discharged at anode.
Hope you get it

hmmmm thnx i got it

 

[Saad Mughal]

i was finding 'displacement reaction' in the options. i get the point tht y is it redox. so should i consider it a rule tht displacement reactions are redox reactions? does this apply everywhere?
aaaaaaaa.......okay i get it...the prblem is,,,u cn never learn to answr such questions. i did have all the knowledge required in this question yet was cluless....It helpd alot! thankyouuuuu!!

Yes you can say that displacement reactions are redox since one element is oxidized and the other is reduced. No extra ions are formed. No problem

 

[Saad Mughal]

hmmmm thnx i got it

 

[A star]

thnx both ov u and what abt nitrates???

basically the reasoning for this is to complicated for O and even As level purposes basically you need to know that sulphate ions are higher in reactivity series so will never be discharged. to make sulphate/nitrates/carbonates ions discharge you also need to break up the anion which is not a feasable process.(OH-) ion is a exception

 

[asma tareen]

basically the reasoning for this is to complicated for O and even As level purposes basically you need to know that sulphate ions are higher in reactivity series so will never be discharged. to make sulphate/nitrates/carbonates ions discharge you also need to break up the anion which is not a feasable process.(OH-) ion is a exception

hmm thnx

 

[Usama Jawad]

if HCl has concentration of 1.43mol/dm^3
what is its concentration in g/dm^3??????
plz also tell formula

 

[TheStallion-Reborn]

if HCl has concentration of 1.43mol/dm^3
what is its concentration in g/dm^3??????
plz also tell formula

moles=given mass/mr. so mr of hcl is 1+35.5=36.5. so 36.5*1.43=52.195. i hope dis helps. can u check the answr in marking scheme so I can be sure if my method is right or not

 

[Saad Mughal]

moles=given mass/mr. so mr of hcl is 1+35.5=36.5. so 36.5*1.43=52.195. i hope dis helps. can u check the answr in marking scheme so I can be sure if my method is right or not

Your method is correct. And that should be the correct answer as well.

if HCl has concentration of 1.43mol/dm^3
what is its concentration in g/dm^3??????
plz also tell formula

Just like TheStallion-Reborn stated, since both the concentrations are in dm^3, you simply have to calculate the mass(g) of 1.43 moles of HCL using the formula (Mass = No. of moles * Mr/Ar) so this would simply get the concentration in g/dm^3.

 

[Snowysangel]

Could someone explain the difference in blood pressure in the arteries, the heart, the veins & the capillaries?

 

[Usama Jawad]

moles=given mass/mr. so mr of hcl is 1+35.5=36.5. so 36.5*1.43=52.195. i hope dis helps. can u check the answr in marking scheme so I can be sure if my method is right or not

Your method is correct. And that should be the correct answer as well.


Just like TheStallion-Reborn stated, since both the concentrations are in dm^3, you simply have to calculate the mass(g) of 1.43 moles of HCL using the formula (Mass = No. of moles * Mr/Ar) so this would simply get the concentration in g/dm^3.

thnx guys,but stallion reborn,this question isnt from past papers but I think you are right