Prelim Chem Thread (3 Viewers)

[drsabz101]

OKAY so I made this thread for anyone who has questions about prelim chemistry ^^ Also for any challenging questions as well .


I guess I'll start off with asking if anyone can explain the Gay Lussac's law with a given example

 

[InteGrand]

OKAY so I made this thread for anyone who has questions about prelim chemistry ^^ Also for any challenging questions as well .


I guess I'll start off with asking if anyone can explain the Gay Lussac's law with a given example

https://en.wikipedia.org/wiki/Gay–Lussac_law#Law_of_combining_volumes

 

[drsabz101]

Thanks Integrand. Can you give an exemplar of a question that may relate to this?

 

[Shuuya]

Thanks Integrand. Can you give an exemplar of a question that may relate to this?

I found a question:

500mL of hydrogen gas and 400mL oxygen gas were inserted in a sealed container and the contents allowed to react. What is the composition of the final gas mixture?

The equation for the reaction is: 2H2(g) + O2(g) ---> 2H2O(g)

 

[drsabz101]

Do we use the formula:

n (moles) = V/STP or SLC by any chances. I don't know what to do first actually

 

[Shuuya]

For this question, you don't need to find the moles because you're given the volumes, and 'The ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers.' So being given the volume of reactants is enough to determine the volume of the products.

2H2(g) + O2(g) ---> 2H2O(g)

So, 2 volumes of H2 react with one volume of O2 to produce 2 volumes of H2O

You need to find the limiting reagent:

If all of the 500mL of H2 is to react, we need only 250mL of O2, as the ratio is 2:1. However, we have 400mL, and therefore O2 is in excess.

So the reaction is:

500 mL of H2 reacts with 250 mL of O2 ----> 500mL of H2O

Since we started with 400mL of oxygen, 150mL remains unreacted, and therefore is still in the container as well as the H2O

So, the composition of the final mixture is 500mL of H2O and 150mL of O2

 

[drsabz101]

Aha thanks! you're really good at explaining chem concepts

 

[Shuuya]

Aha thanks! you're really good at explaining chem concepts

No worries and thanks, I'm glad to be able to help!

 

[drsabz101]

does this also come up under yr 12 chem?

 

[Shuuya]

does this also come up under yr 12 chem?

Its year 11

 

[drsabz101]

Okay, but do we need to know this for yr 12 as well?

 

[Shuuya]

Okay, but do we need to know this for yr 12 as well?

There aren't any dot points in the year 12 syllabus on this particular concept, but it probably would come into calculation questions

 

[drsabz101]

okay then. Thankyou

 

[the_matrix]

Isn't Guy Lussac's law year 12 content? or is this like the temporary HSC thread as well? :/

Okay, but do we need to know this for yr 12 as well?

According to my chem teacher who is a HSC marker, you get a mark for just reciting his law in your response lol

 

[DatAtarLyfe]

No lussac is most definitely prelim

 

[eyeseeyou]

Gay Lussac is in the prelim syllabus not the HSC. You'll encounter him in the Module Metals

 

[drsabz101]

Yeah it is under the topic metals

 

[leehuan]

Isn't Guy Lussac's law year 12 content? or is this like the temporary HSC thread as well? :/


According to my chem teacher who is a HSC marker, you get a mark for just reciting his law in your response lol

I have never seen it get asked in ANY HSC question thus far.

The one that always gets examined on is Le Chatelier's Principle

 

[drsabz101]

nope

 

[drsabz101]

Do we have to have already studied the modules, 'water' and ' energy' to begin making notes for yr 12 chem? Are there things that I have to had memorized and studied from these topics for yr 12 content to make sense?

I have gone through the first 2 terms of chem. And wanted to get a head start on the yr 12 content