When calculating eq. constant... (1 Viewer)

[dRscarf]

When you calculate the equilibrium constant (K), do you need to put in units? Some people around me are saying yes and others no... so I'm pretty confused.

 

[danz90]

The equilibrium constant is only measuring the extent to which the forward reaction is occuring/favoured at particular conditions.
If conditions such as pressure and temperature of the reaction are given, make sure you answer in this format:

Kc = __ at T°C and ___kPa or ___atm

For calculating, just sub in the equilibrium concentrations of the products and reactants into the equilibrium expression. Always round off to the lowest significant figure present in the question.

 

[henry08]

The syllabus dotpoint specifically states that no units are needed for equilibrium constant.

 

[gezzill]

mol/L i think, unless it specifically says.

 

[minijumbuk]

No units.

 

[tommykins]

回复: Re: When calculating eq. constant...

No units.

This.

 

[danz90]

Re: 回复: Re: When calculating eq. constant...

There's no units for equilibrium constant... its just a figure that shows the extent to which the forward reaction in an equilibrium reaction is favoured, at a particular temperature.

 

[cwag]

still on the same topic....iv seen many calculations in books where they don't seem to involve any solids or liquids in the K expression.....are they wrong. i thought it was plainly [products]/[reactants] no exceptions.?

 

[minijumbuk]

Umm, I think it's only aqueous and gas.

 

[cwag]

Umm, I think it's only aqueous and gas.

thanks...i think thats what it is....can someone clarify this?

 

[Undermyskin]

It's correct, I think. I've never dealt with a K questions that have solid in it, to my ignorance, I suppose.

But revising what we need to do, I can prove it.

What we need to calculate K are the []s of chemicals involved. These can only be applied to aqueous solutions or gases only, right? Have you ever had a concentration of any solids? This is because the 'concentration' of a solid is preserved all the time. Taking a crystal of salt as an example. The number of molecules of NaCl/ the volume that crystal occupies = constant, yeah? Because even if adding more salt into an already concentrated solution, the extra settles to the bottom, joining the solid particles. And since the density of solid salt is the same at certain temperature and pressure, 'the concentration' is also the same. The more salt you add, the larger volume it occupies with the more molecules in there.

 

[minijumbuk]

It's correct, I think. I've never dealt with a K questions that have solid in it, to my ignorance, I suppose.

But revising what we need to do, I can prove it.

What we need to calculate K are the []s of chemicals involved. These can only be applied to aqueous solutions or gases only, right? Have you ever had a concentration of any solids? This is because the 'concentration' of a solid is preserved all the time. Taking a crystal of salt as an example. The number of molecules of NaCl/ the volume that crystal occupies = constant, yeah? Because even if adding more salt into an already concentrated solution, the extra settles to the bottom, joining the solid particles. And since the density of solid salt is the same at certain temperature and pressure, 'the concentration' is also the same. The more salt you add, the larger volume it occupies with the more molecules in there.

2007 Industrial chemistry section. There was solid in the equilibrium. You just have to ignore it in the equilibrium expression.

 

[tommykins]

回复: Re: When calculating eq. constant...

Solids are ignored, along with pure liquids (l)

 

[Trebla]

Re: 回复: Re: When calculating eq. constant...

Solids are ignored, along with pure liquids (l)

...because they have extremely high concentration which would make your K useless, if you included it.

 

[tommykins]

回复: Re: 回复: Re: When calculating eq. constant...

...because they have extremely high concentration which would make your K useless, if you included it.

yeah i cbf'd writing out the reasoning. lol.

 

[cwag]

It's correct, I think. I've never dealt with a K questions that have solid in it, to my ignorance, I suppose.

But revising what we need to do, I can prove it.

What we need to calculate K are the []s of chemicals involved. These can only be applied to aqueous solutions or gases only, right? Have you ever had a concentration of any solids? This is because the 'concentration' of a solid is preserved all the time. Taking a crystal of salt as an example. The number of molecules of NaCl/ the volume that crystal occupies = constant, yeah? Because even if adding more salt into an already concentrated solution, the extra settles to the bottom, joining the solid particles. And since the density of solid salt is the same at certain temperature and pressure, 'the concentration' is also the same. The more salt you add, the larger volume it occupies with the more molecules in there.

Yea that makes sense.... thanks everyone

 

[Almatari]

Units depends on the K expression

units for [] is mol/L
but if it is []^2, then the units are squared as well (mol/L)^2
and so on.......

 

[chuboy]

Units depends on the K expression

units for [] is mol/L
but if it is []^2, then the units are squared as well (mol/L)^2
and so on.......

No, fail.

The K value is the ratio of products to reactants in an equilibrium system. OBVIOUSLY NO UNITS.

 

[boxhunter91]

No, fail.

The K value is the ratio of products to reactants in an equilibrium system. OBVIOUSLY NO UNITS.

LOL mate this was ages ago.

 

[chuboy]

True >.<

Well even so, this should be of some relevance since the exam is tomorrow.