ssNake's Chemistry [u2] Q's

[REBORN]

um copper is on the right hand side of the electrochemical series and hence a reductant...

[b^3]

The reactants we have are K⁺, Cl^-, Cu²⁺ and H₂O (as it is aqueous)
so the reactions we have to look at in this order are
Cl₂(g)+2e^---->2Cl^-(aq)
Cu²⁺(aq)+2e^---->Cu(s)
2H₂O(l)+2e^---->H₂(g)+2OH^-(aq)
K⁺(aq)+e^---->K(s)

The ones in red are the ones we have

For a spontaneous reaction to occur, they have to have a negative gradient like this
            \
             \
              \
               \
So since this is not satisfied, there will be no spontaneous reaction

[illuminati]

um copper is on the right hand side of the electrochemical series and hence a reductant...

Yeah, but its not elemental copper in solution, it's the Cu 2+ ion... which is an oxidant...

[REBORN]

OH right.

I get it.

[Russ]

and H₂O (as it is aqueous)

Pointing out the importance of recognizing this...I lost 5 marks on a SAC for missing the fact that aqueous reactions have water in them...don't do that

[b^3]

and H₂O (as it is aqueous)

Pointing out the importance of recognizing this...I lost 5 marks on a SAC for missing the fact that aqueous reactions have water in them...don't do that

Yeh, for yr 12, the exam writers always like to throw in a 'molten' or 'aqueous' solution of NaCl or Al... or whatever it is, just to trick everyone.
By this I am refering to electrolysis.

[REBORN]

4L of hydrogen gas is collected in a syringe. The pressure and the temperature of the gas inside the syringe are both doubled. When this happens, the volume of the hydrogen gas, in L, in the syringe would be?

A 1
B 4
C 6
D 16

[b^3]

So we know the basic equation PV=nRT right.
n (the number of mol) and R (the gas constant) won't change here
so we know they are constant before and after
so rearrange nR=PV/T, k=PV/T
so before k=P₁V₁/T₁
and we know that after Pressure and temperature are doubled so P₂=2P₁ and T₂=2T₁
so afterwards
k=P₂*V₂/T₂
we any volume, and since they are ratios, k can equal
so V₂=T₂/P₂
=2T₁/2P₁
=T₁/P₁
since this is the ratio is the same before and after, the volume will still be 4L so B is the answer.

NOTE: I think I may have overcomplicated this but it should work anyway, I use PV=nRT instead of P1V1=.... since we can always get the other equations from this one.

[Russ]

NOTE: I think I may have overcomplicated this but it should work anyway, I use PV=nRT instead of P1V1=.... since we can always get the other equations from this one.

You did but it's still right. I just said mentally "P is on the left, T is on the right and they change proportionally so there's no change"

[b^3]

NOTE: I think I may have overcomplicated this but it should work anyway, I use PV=nRT instead of P1V1=.... since we can always get the other equations from this one.

You did but it's still right. I just said mentally "P is on the left, T is on the right and they change proportionally so there's no change"

Yeh thats exaclty what I was thinking to myself when I hit the same ratio, but I put the effort into typing the rest out so I wasn't deleting it.

I always seem to overcomplicate everything in life.

[SamiJ]

What does iron (iii) nitrate plus iron (ii) sulfate become?
And iodine plus potassium iodine?

[REBORN]

RE: kinetic molecular theory of gases

pressure of a gas is due to no. of collisions of the gas particles with the walls of the vessel AND/OR with each other?

[Mao]

RE: kinetic molecular theory of gases

pressure of a gas is due to no. of collisions of the gas particles with the walls of the vessel AND/OR with each other?

Against the walls. It is the forced experienced by a unit surface in contact with the gas. (specifically, the force perpendicular to the surface)

[REBORN]

Design a flowchart to show how the salt content of a savoury spread could be determined by gravimetric analysis.

[Lasercookie]

Design a flowchart to show how the salt content of a savoury spread could be determined by gravimetric analysis.

We haven't covered gravimetric analysis in class yet, but I imagine you could just convert this: http://en.wikipedia.org/wiki/Gravimetric_analysis#Procedure into a flowchart using simpler terminology (and of course replacing all the general words like 'sample' and solution to refer to the savoury spread).