Chemistry: Post your doubts here!

[smartangel]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Q34..after 20 mins rxn is complete..mass of mg used is same so how can sukfuric acid produce more gas? statement 3 is correct according to ms..how?

 

[Casablanca]

from wikipedia

lemme expain:
example of a dimer is Al2Cl6
its a dimer of AlCl3
so you can think of a dimer as two same molecules bonded to each other for ex AlCl3+AlCl3=al2cl6

So... is C10H12 a dimer of C5H6?

 

[smartangel]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
Q6..plz help me out with this one..

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Q34..after 20 mins rxn is complete..mass of mg used is same so how can sukfuric acid produce more gas? statement 3 is correct according to ms..how?

Answer for question 35
the reactions will be
Mg + 2 CH3COOH <=> Mg(CH3COO)2+ H2(g)
Mg + H2SO4 → MgSO4 + H2


1 After 2 minutes, the sulfuric acid is at a higher temperature than the ethanoic acid.
2 After 2 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
this is because the sulfuric acid is a stronger oxidising agent and therefore will be quicker in forming the magnesium sulfate and hydrogen than ethanoic acid .and when it does form , bond forming is exxothermic and so it is at an higher temperature
3 After 20 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
This is because the reaction between ethanoic acid and magnesium is in equilibrium which means the reaction never reaches completion.Moreover , the stoichichemtry of the equilibrium shows us that more reactants are present than products (reactants =3m products =2m)

 

[furry.panda]

17 Which statement explains the observation that magnesium hydroxide dissolves in aqueous ammonium chloride, but not in aqueous sodium chloride?

AThe ionic radius of the NH4+ ion is similar to that of Mg2+ but not that of Na+.
BNH4Cl dissociates less fully than NaCl.
CThe ions Na+ and Mg2+ are isoelectronic (have the same number of electrons).
DThe ion NH4+ acts as an acid.


Ans: D

Can someone please explainn? thanks in advance

 

[smzimran]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
Q.5, Q.11 please?

AoA,
I have solved q5 in this thread before, search it

q11:
A is correct because when you acidify pool water, that means you add H+ ions and these H+ ions will react ith OH- ions
The concentration of OH- will decrease and equilibrium will shift towards right and more HOCL will be produced

 

[Osake]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_ms_1.pdf

does anyone know how to get answers to q no 3O and 38??
any help will be GREATLY appreciated ^_^

yield = Actual yield/measured yield x100 right?
we know there is 30 g of ethanoic acid
so Measured yield = 30(98)/60 x100 = 45 , closest to 50 so answer is C

 

[KurayamiKimmi]

So... is C10H12 a dimer of C5H6?

yes

 

[nerdybookworm]

URGEEEEEENNNTTTTTTTT...OCTO NOV...2011 VARIENT 11 PAPER 1...Q 6,914,15,20,23,25,28,29...plzz....

 

[Casablanca]

17 Which statement explains the observation that magnesium hydroxide dissolves in aqueous ammonium chloride, but not in aqueous sodium chloride?

AThe ionic radius of the NH4+ ion is similar to that of Mg2+ but not that of Na+.
BNH4Cl dissociates less fully than NaCl.
CThe ions Na+ and Mg2+ are isoelectronic (have the same number of electrons).
DThe ion NH4+ acts as an acid.


Ans: D

Can someone please explainn? thanks in advance

MgOH is basic, so the ammonium chloride neutralizes it, since it's acidic.

 

[Casablanca]

yes

Okay, got it. Thanks. =^.^=

 

[smartangel]

Answer for question 35
the reactions will be
Mg + 2 CH3COOH <=> Mg(CH3COO)2+ H2(g)
Mg + H2SO4 → MgSO4 + H2


1 After 2 minutes, the sulfuric acid is at a higher temperature than the ethanoic acid.
2 After 2 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
this is because the sulfuric acid is a stronger oxidising agent and therefore will be quicker in forming the magnesium sulfate and hydrogen than ethanoic acid .and when it does form , bond forming is exxothermic and so it is at an higher temperature
3 After 20 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
This is because the reaction between ethanoic acid and magnesium is in equilibrium which means the reaction never reaches completion.Moreover , the stoichichemtry of the equilibrium shows us that more reactants are present than products (reactants =3m products =2m)

how do u knw its in equilibrium?

 

[smzimran]

17 Which statement explains the observation that magnesium hydroxide dissolves in aqueous ammonium chloride, but not in aqueous sodium chloride?

AThe ionic radius of the NH4+ ion is similar to that of Mg2+ but not that of Na+.
BNH4Cl dissociates less fully than NaCl.
CThe ions Na+ and Mg2+ are isoelectronic (have the same number of electrons).
DThe ion NH4+ acts as an acid.


Ans: D

Can someone please explainn? thanks in advance

Very simple
Mg(OH)2 is a base and it will react with an acid
It will not react with NaCl as it is not an acid
It reacts with NH4Cl because it acts as an acid because NH4+ ion donates a proton (Bronsted Lowry acid)

 

[KurayamiKimmi]

yield = Actual yield/measured yield x100 right?
we know there is 30 g of ethanoic acid
so Measured yield = 30(98)/60 x100 = 45 , closest to 50 so answer is C

do you mean theoretical yied by measured yield ?=O

 

[geek101]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf Q4 someoneeee! pretty please!

 

[KurayamiKimmi]

how do u knw its in equilibrium?

because it is a weak acid -weak acids form equilibriums

 

[KurayamiKimmi]

Okay, got it. Thanks. =^.^=

anytime ^_^

 

[smartangel]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
Q6..plz help me out with this one.

 

[gary221]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
Q6..plz help me out with this one..

Here use d eqn pv = nRT, u know the pressure = 101kPa
To find no of moles of ice, find the mass, d*v = 1 g, n Mass/Mr...so no of moles = 0.0556
R = 8.213
T = 596 K
Substitute d values, to get d ans, C

 

[gary221]

Hey guys need help with this!!