Biology; Chemistry; Physics: Post your doubts here!

[nidz]

seems immposible

Doesnt this happen?

BaNO3 + H2SO4---> BaSO4 + HNO3

 

[Amen]

Atlast after a hell lot of chemistry, I have a biology question "How do we identify by looking at the petals, anthers and stigma of a plant if it's wind pollinated or insect pollinated?" there are a lot of questions regarding this, and most of the time I fail to answer them correctly!

wind pollinated insect pollinated
1.large brightly coloured petals with nector guides1.small nd dull coloured petals
with nector guides absent
2.anthers have non pendulous filaments2.anthers have long pendulous filament
3.stigma is small nd compact 3.stigma is long and feathery

 

[Amen]

eg

BaCl2 + H2SO4 = BaSO4 + 2HCl

(by the way i just made it up so an ionic equation of this reaction might not be possible) :O

it is possible(i guess) as BaCl and HCl r both aq.
Ba*+(SO4)*=BaSO4

 

[Suchal Riaz]

Can anyone help me with ionic equations please? I can do the simpler ones in which there is only one displacement. But when it comes to double displacement, i really suck at them.

it is very simple, as catine of more reactive metal will want to combine will anine which is more stable.
if u but AgNO3 and NaCl in aqueous form, Na being more reactive will prefer to combine will no3 which is more more stable. so Ag and Cl will combine. in this reactive NaNo3 is soluble but AgCl is not, therefore u will see white precipitate of AgCl. if both would have been soluble then there would be no precipitate.
actually they need to be in aqueous form because ions can only more in aqueous form so we need both of these salts to be soluble.
Ag-(aq) + Cl+(aq) + Na(aq)+ + NO3-(aq) ---> AgCl(s) + Na+(aq) + NO3(aq)-,
Na and NO3 will be still seperate ions so they will be written as ions in both sides, they wont combine until they are in solid form. AgCl however will combine as it is in solid form. u dont write Na and NO3 as they are in both sides. net equation will be this:
Ag-(aq) + Cl+(aq) => AgCl(s)
it is not necessary that more reactive ions will remain and less reactive will precipitate.
u should know that when u dissolve something lets say nacl, it is no more nacl, it is na+ and cl- seperately in water untill u dry it out. although silver chloride won't dissolve so it will be AgCl even in water.
spectator ions will be in both sides(show complete ions in complete equations) so dont show them in net equations.
in o level u r asked to write net ionic equation not complete

 

[Saad Mughal]

TheStallion-Reborn

We won. Yay!
TheStallion-Reborn

 

[Kamihus]

it is very simple, as catine of more reactive metal will want to combine will anine which is more stable.
if u but AgNO3 and NaCl in aqueous form, Na being more reactive will prefer to combine will no3 which is more more stable. so Ag and Cl will combine. in this reactive NaNo3 is soluble but AgCl is not, therefore u will see white precipitate of AgCl. if both would have been soluble then there would be no precipitate.
actually they need to be in aqueous form because ions can only more in aqueous form so we need both of these salts to be soluble.
Ag-(aq) + Cl+(aq) + Na(aq)+ + NO3-(aq) ---> AgCl(s) + Na+(aq) + NO3(aq)-,
Na and NO3 will be still seperate ions so they will be written as ions in both sides, they wont combine until they are in solid form. AgCl however will combine as it is in solid form. u dont write Na and NO3 as they are in both sides. net equation will be this:
Ag-(aq) + Cl+(aq) => AgCl(s)
it is not necessary that more reactive ions will remain and less reactive will precipitate.
u should know that when u dissolve something lets say nacl, it is no more nacl, it is na+ and cl- seperately in water untill u dry it out. although silver chloride won't dissolve so it will be AgCl even in water.
spectator ions will be in both sides(show complete ions in complete equations) so dont show them in net equations.
in o level u r asked to write net ionic equation not complete

well explained
but please note its cation and anion
Ag will be positive and Cl negative

 

[usama321]

it is very simple, as catine of more reactive metal will want to combine will anine which is more stable.
if u but AgNO3 and NaCl in aqueous form, Na being more reactive will prefer to combine will no3 which is more more stable. so Ag and Cl will combine. in this reactive NaNo3 is soluble but AgCl is not, therefore u will see white precipitate of AgCl. if both would have been soluble then there would be no precipitate.
actually they need to be in aqueous form because ions can only more in aqueous form so we need both of these salts to be soluble.
Ag-(aq) + Cl+(aq) + Na(aq)+ + NO3-(aq) ---> AgCl(s) + Na+(aq) + NO3(aq)-,
Na and NO3 will be still seperate ions so they will be written as ions in both sides, they wont combine until they are in solid form. AgCl however will combine as it is in solid form. u dont write Na and NO3 as they are in both sides. net equation will be this:
Ag-(aq) + Cl+(aq) => AgCl(s)
it is not necessary that more reactive ions will remain and less reactive will precipitate.
u should know that when u dissolve something lets say nacl, it is no more nacl, it is na+ and cl- seperately in water untill u dry it out. although silver chloride won't dissolve so it will be AgCl even in water.
spectator ions will be in both sides(show complete ions in complete equations) so dont show them in net equations.
in o level u r asked to write net ionic equation not complete

thanks for explaining it It seems a lot easier now

 

[Suchal Riaz]

well explained
but please note its cation and anion
Ag will be positive and Cl negative

oops switched signs

 

[ijlalm]

Maybe this will help
Break every compound in ions except insoluble ones (you have to revise the solubility chart for that)
for example
BaCl2 + H2SO4 = BaSO4 + 2HCl
Ba2+, Cl- , Cl-, H+,H+,SO42-=do not write BaSO4 in ions(insoluble) , H+,H+,Cl-,Cl-
Cancel the same ions on both sides
So Ba2+ + SO42- = BaSO4
Tada!!!

 

[Mustafa Malik]

http://papers.xtremepapers.com/CIE/...l O Level/Chemistry (5070)/5070_s10_qp_12.pdf
Can anyone explain Quesstion 20 and 21??
Plz anyone reply me soon. For 20 ans is C and for 21 A..

 

[Saad Mughal]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s10_qp_12.pdf
Can anyone explain Quesstion 20 and 21??
Plz anyone reply me soon. For 20 ans is C and for 21 A..

The answer for 20 is C. The oxide of the element X is a catalyst. We know that most catalysts are from the transition metals, so among the 4 options, either D or C are transition elements, A is argon and B is magnesium. C is Manganese and is the answer since Lead (D) oxide and dioxide are good oxidizing agents rather than catalysts.
For 21, the answer is D, Sodium has a low melting point AND density.

 

[usama321]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s10_qp_12.pdf
Can anyone explain Quesstion 20 and 21??
Plz anyone reply me soon. For 20 ans is C and for 21 A..

transition elements are mostly catalysts. So, from the list, C is a transition element. By the way, for 21, the answer seems to be D, for alkali metals do not have very high melting points, and C can't be the answer as it states poor conductivity.

 

[asma tareen]

can neutralization occur by insoluble bases???

 

[Saad Mughal]

can neutralization occur by insoluble bases???

Yes, neutralization occurs whenever a salt and water are formed (on reaction with acid of course).

 

[asma tareen]

Yes, neutralization occurs whenever a salt and water are formed (on reaction with acid of course).

hmm kay thnx

 

[usama321]

24
Which reactants could be used safely to prepare potassium chloride?
A aqueous potassium hydroxide and dilute hydrochloric acid
B aqueous potassium sulphate and aqueous sodium chloride
C potassium and aqueous sodium chloride
D potassium and dilute hydrochloric acid
the answer is A. Why can't it be B?

 

[asma tareen]

A
maybe??

 

[usama321]

A
maybe??

read my last line

 

[Saad Mughal]

24
Which reactants could be used safely to prepare potassium chloride?
A aqueous potassium hydroxide and dilute hydrochloric acid
B aqueous potassium sulphate and aqueous sodium chloride
C potassium and aqueous sodium chloride
D potassium and dilute hydrochloric acid
the answer is A. Why can't it be B?

C and D will be vigorous reactions, we can't react them safely.
B is not possible (for forming KCl), the reason being that Sulphate ions are more stable and reactive than Chloride ions hence the Potassium ion prefers to be with the Sulphate ion rather than the less stable chloride ion therefore the reaction is not feasible.

 

[asma tareen]

lol sorry cux we dont use precipitation for soluble salts

read my last line