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March 29, 2024, 07:19:26 pm

Author Topic: VCE Chemistry Question Thread  (Read 2313674 times)  Share 

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nhmn0301

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Re: VCE Chemistry Question Thread
« Reply #1140 on: July 11, 2014, 12:22:23 am »
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Could someone please explain why halving the volume (doubling the pressure) of an equilibrium will have the effect of a net forward reaction. Whereas when increasing pressure on the equilibrium reaction, there will be no effect?

Thanks :)
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For equilibrium, it would be insufficient if you don't specify the equation you are referring to. I made a post a while ago here Re: Rod's Chemistry 3/4 Questions Thread so please have a look through it and let me know if you need any further clarifications :D!
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Reus

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Re: VCE Chemistry Question Thread
« Reply #1141 on: July 11, 2014, 12:28:27 am »
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Thanks guys :)

Haha thought about posting the reaction too but cbf'd :P
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #1142 on: July 11, 2014, 11:09:23 am »
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Could someone please explain why halving the volume (doubling the pressure) of an equilibrium will have the effect of a net forward reaction. Whereas when increasing pressure on the equilibrium reaction, there will be no effect?

Thanks :)

When the volume is halved, the pressure increases. In order to partially oppose this increase in pressure, the reaction that will be favoured will be the one that produces fewer molecules. In this way, pressure can be partially reduced. All you would then need to do is read your equation, and from that, look at which direction reaction produces FEWER molecules based on the mole ratios. The reaction that produces fewer particles will be favoured, and a net reaction would occur in that direction.

hyunah

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Re: VCE Chemistry Question Thread
« Reply #1143 on: July 11, 2014, 11:30:16 am »
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can someone please help me with question 11?

thank you

soNasty

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Re: VCE Chemistry Question Thread
« Reply #1144 on: July 11, 2014, 02:40:42 pm »
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What exactly is the concentration fraction and how does it compare to an equilibrium constant?

Rishi97

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Re: VCE Chemistry Question Thread
« Reply #1145 on: July 11, 2014, 02:46:53 pm »
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What exactly is the concentration fraction and how does it compare to an equilibrium constant?

I like to think of the concentration fraction like a ratio between the products and reactants. Only temperature effects the equilibirum constant but the concentration fraction can be effected by mostly everything.
eg. If I increase the concentration of a reactant, there will be more products produced so the concentration fraction will increase. BUT the equilibrium constant remains the same as there is no change is temperature.
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soNasty

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Re: VCE Chemistry Question Thread
« Reply #1146 on: July 11, 2014, 02:56:04 pm »
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Oh ok. Thanks rish!!

alchemy

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Re: VCE Chemistry Question Thread
« Reply #1147 on: July 11, 2014, 03:13:23 pm »
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Which one of the following acts as a base when hydrofluoric acid is dissolved in an aqueous solution of sodium chloride?
a. Cl–
b. HF
c. H2O
d. NaCl
e. Na+

The answer is C. Can someone explain why.

Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #1148 on: July 11, 2014, 03:31:33 pm »
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can someone please help me with question 11?

thank you

When a galvanic cell is set up, you have two separate half-cells that are connected by connecting wires and a salt-bridge, in order to complete the circuit and enable its function. In a dry cell, a si-permeable membrane is used, that allows the two components to be separated, yet still connected by employing a membrane with a specific degree of permeability, which is how a dry cell ultimately functions.

lzxnl

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Re: VCE Chemistry Question Thread
« Reply #1149 on: July 11, 2014, 10:02:50 pm »
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Which one of the following acts as a base when hydrofluoric acid is dissolved in an aqueous solution of sodium chloride?
a. Cl–
b. HF
c. H2O
d. NaCl
e. Na+

The answer is C. Can someone explain why.

NaCl, or Cl-, won't act as a base as Cl- is the conjugate base of an exceedingly strong acid (HCl), so it has no acid-base properties. Therefore neither a nor d is right. E is definitely wrong as Na+ ions don't do anything either. b is wrong as HF is the acid. c is correct as when you dissolve HF in water, a portion of the HF reacts by the following reaction
HF (aq) + H2O (l) <=> F- (aq) + H3O+ (aq)

Here the water accepts a proton and thus acts as a base
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alchemy

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Re: VCE Chemistry Question Thread
« Reply #1150 on: July 12, 2014, 12:07:46 am »
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can someone please explain to me how to do part c) and e)?

thank you

Use the data book for part c. You will see that butanoic acid is weaker than ethanoic acid because butanoic acid has a lower Ka value than ethanoic acid. Therefore, for part e, the Ph of a similar solution of ethanoic acid would be lower.

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Re: VCE Chemistry Question Thread
« Reply #1151 on: July 12, 2014, 07:38:08 am »
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NaCl, or Cl-, won't act as a base as Cl- is the conjugate base of an exceedingly strong acid (HCl), so it has no acid-base properties. Therefore neither a nor d is right. E is definitely wrong as Na+ ions don't do anything either. b is wrong as HF is the acid. c is correct as when you dissolve HF in water, a portion of the HF reacts by the following reaction
HF (aq) + H2O (l) <=> F- (aq) + H3O+ (aq)

Here the water accepts a proton and thus acts as a base

Very solidly explained :D
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psyxwar

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Re: VCE Chemistry Question Thread
« Reply #1152 on: July 12, 2014, 11:41:03 am »
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What exactly is the concentration fraction and how does it compare to an equilibrium constant?
I've actually never heard this term before. Isn't it Q, the reaction quotient?
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Reus

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Re: VCE Chemistry Question Thread
« Reply #1153 on: July 12, 2014, 11:44:53 am »
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I've actually never heard this term before. Isn't it Q, the reaction quotient?
Same here, until I did that particular question haha.
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lzxnl

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Re: VCE Chemistry Question Thread
« Reply #1154 on: July 12, 2014, 12:27:41 pm »
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I've actually never heard this term before. Isn't it Q, the reaction quotient?

Concentration fraction and reaction quotient refer to the same thing
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