Unit 4 Questions MEGATHREAD!

[luken93]

Due to popular demand of last semester's questions thread (especially the week before exams!), we may as well get another thread going!

No question is too silly, stupid or out of context (within theory ), so post it up and I'm sure one of us will get back to you ASAP!

We're all in this together   

[b^3]

Good idea luken93, and it might be time to change your countdown to the unit 4 exam. 

[luken93]

Good idea luken93, and it might be time to change your countdown to the unit 4 exam. 

Hahaha yeah, good point.

[Lols123]

In the reaction 2SO3 --> 2SO2 + O2
0.10 mol SO3 is added to a 1L vessel. At equilibrium, there is 0.08 mol of the SO3 remaining. Calculate the value of K.

[luken93]

Since SO3 has lost 0.02 mol;

SO2 will gain (0.02/2) x 2 = 0.02 mol
O2 will gain (0.02/2) x 1 = 0.01 mol

Convert each to concentration;

[SO3] = 0.08
[SO2] = 0.02
[O2] = 0.01

K = ([SO2]^2 x [O2])/[SO3]^2
= (0.02^2 x 0.01)/0.08^2
= 0.000625

Hopefully I haven't made a mistake

[ruchika5]

Hey people, just a random question but is Chapter 18 (The Chemical Industry: risk and rewards) in the Heinemann textbook relevant to the course?? As in, can it be examined, or is it just a general chapter leading up to the industrial production section? Thanks

[Gilla1]

why does the temperature of endothermic reactions decrease if it absorbs energy?

[b^3]

I'm not 100% sure on this but isn't it because the change in H= energy which is stored in the bonds and not as the kinetic of the particles, with the kinetic energy being the contributing factor to temperature?

[tony3272]

why does the temperature of endothermic reactions decrease if it absorbs energy?

You can see the reaction as taking in heat in order for it to occur, and hence the heat of its surroundings is decreased.

[luken93]

Since endothermic requires heat to be absorbed in order for the bonds to be broken in molecules, heat is taken out of the surrounding environment according to the Law of Conservation of Energy - where energy is not lost or destroyed,but rather converted into another form of energy. In this case heat energy is converted to kinetic so that there is sufficient energy to break the bonds in molecules.

Probably a better explanation to this, but hopefully it answers everything

[DisaFear]

2HI --> H2 + I2 (hydrogen gas and iodine gas)

At equilibrium, will the conc. of H2 and I2 be the same?

[HenryP]

2HI --> H2 + I2 (hydrogen gas and iodine gas)

At equilibrium, will the conc. of H2 and I2 be the same?

Yes they will be, since any HI that reacts will produce equal amounts of H2 and I2. Assuming you only had HI in the vessel to begin with.

[DNAngel]

Hi guys,

I'm having trouble atm on how to sketch concentration vs time graphs. The part that confuses me is the direction that the curve of each reactant/product is moving (either up/down)

[jane1234]

Hi guys,

I'm having trouble atm on how to sketch concentration vs time graphs. The part that confuses me is the direction that the curve of each reactant/product is moving (either up/down)

Do you have any specific examples of questions you need help with?

[DNAngel]

Do you have any specific examples of questions you need help with?

For example,

The equilibrium constant for the reaction H_2(g) + I_2(g) <---> 2HI _(g) is 48.7 at 400^oC

Sketch a graph showing concentration against time for this system.