James ruse preliminary past paper, any help? (1 Viewer)

[girlworld_club]

Can someone explain how to do Q17 of this paper. It is preliminary chem.

http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2006JamesRuseHalfYearly.pdf

thanks in advance.

 

[girlworld_club]

Also, what is the reaction between aluminum and iodine. Please show full working of how you came to your answer thanks

 

[Aykay]

1. C, A, E, B, D.
Just count how many reactions each metal has.

2. i)
3B(s) + E3+(aq) ----> 3B2+(aq) + 2E(s)

We know this because it is a redox reaction.
States can be found because it is given that B is a solid, and ions are aqueous.

ii)
B is more reactive so it is oxidised.

So the equations would be:

B(s) --> B2+(aq) + 2e-
E3+(aq) + 3e- --> E(s)

This is basically found from part i) and also the fact that a reaction is observed.

 

[Aykay]

Also, what is the reaction between aluminum and iodine. Please show full working of how you came to your answer thanks

I + Al --> AlI3

It's ionic, and Al is 3+.

 

[hayabusaboston]

meh aykay got the answer

 

[girlworld_club]

thanks i get everything however still a little confused with how you got your solution to 2i)??

 

[dalonga]

Can someone explain how to do Q17 of this paper. It is preliminary chem.

http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2006JamesRuseHalfYearly.pdf

thanks in advance.

Here are the solutions

 

[theind1996]

Here are the solutions

lol

 

[girlworld_club]

i still don't get how they got B +2 for the product side of the equation. question b i)

 

[Aykay]

i still don't get how they got B +2 for the product side of the equation. question b i)

The question tells you that the cation is B2+.

Because there's a reaction between B and the E3+ cation, the E3+ become E and the B becomes B2+.
It's a simple redox reaction.

 

[girlworld_club]

hmmm. how do we know that the valency of B is 2?
still a bit confused.

 

[cutemouse]

hmmm. how do we know that the valency of B is 2?

It's been a while since HSC Chem, but don't you use the periodic table? :\

 

[girlworld_club]

B is an unknown element (metal) so you can not use the periodic table.

 

[cutemouse]

B is an unknown element (metal) so you can not use the periodic table.

If I recall correctly, most metals have a valence of 2+...

 

[girlworld_club]

"most", it could also be a +1, or +3
there is no room for guessing.

 

[nightweaver066]

"most", it could also be a +1, or +3
there is no room for guessing.

The question states the metal ions and shows the ion of B to be B2+.

The safest and most correct way to use the ion in the equation would then be B2+.

 

[Fizzy_Cyst]

2. i)
3B(s) + E3+(aq) ----> 3B2+(aq) + 2E(s)

Should be:
3B(s) + 2E3+(aq) ----> 3B2+(aq) + 2E(s)

 

[J-Wang]

the question tells u that its valency is 2. it cant get much more basic than that