Chemistry Strikes Again! (1 Viewer)

[Finx]

Sorry, but I really need to check these answers =P

What volume of oxygen is required for the complete combustion of 125mL of butene gas (C4H8) and what volume of CO2 is formed? (All volumes are measured at the same temp. and press.)

Since they're all gases at the same temperature and pressure, I assumed Guy Lussac's Law in the equation.

6xO2 + C4H8 ---> 4xH2O + 4xCO2
6.......... : 1............. : 4.......... : 4
750mL : 125mL : 500mL : 500mL

So I got the answer "750mL of oxygen is required for combustion and 500mL of CO2 is formed".

Is this correct?

Thanks in advance =]

 

[minijumbuk]

Yes, it is right. But if it was a 2 mark question, you'd only get one, because you didn't explain Gay Lussac's law and apply it in this situation.

 

[Finx]

Yes, it is right. But if it was a 2 mark question, you'd only get one, because you didn't explain Gay Lussac's law and apply it in this situation.

I seriously doubt I would need to explain Guy Lussac's law. I might need to state that "Since all components are gases and the same temperature and pressure applies, assume Guy Lussac's law."

Actually, I seriously doubt I would need to even state that. Marks are given for working and correct steps/structure, not explaining what laws or formulas you use.

 

[minijumbuk]

Alright, then you can learn through experience.

Because "750mL of oxygen is required for combustion and 500mL of CO2 is formed" does not show any working at all.

 

[Finx]

The 6:1:4:4 is working, and so is the volume ratios.

 

[minijumbuk]

Oh. I thought you just wrote the things you said after "answer" and in quotation marks.

Nevertheless, if teachers use that excuse against you, and say that you did not explain Gay Lussac's law, who are you to argue? I know it may not seem relevant, but trust me, they've done this to me before.

Oh yea, and you should always choose to write more rather than less. Writing more does not hurt, and you've got plenty of time to write more, more more =)

It may or may not earn you extra marks, but it leaves the marker a good impression, and it might just tweak things a little when they come to marking other questions. It's better to eliminate the risk of losing marks anyway. That's the difference between a middle band 6 and a top band 6 student.

 

[Finx]

Hehe no worries. I'd include the reaction formula, molar and volume ratios in the process, then finish with the statement.

My chem teacher works incredibly fast when he explains these things, and often only comes up with that amount of data for his answer.

Nevertheless, I was just wondering if it was right. Thanks =D

 

[dux&src]

Hehe no worries. I'd include the reaction formula, molar and volume ratios in the process, then finish with the statement.

My chem teacher works incredibly fast when he explains these things, and often only comes up with that amount of data for his answer.

Nevertheless, I was just wondering if it was right. Thanks =D

I hope i get a brilliant chemistry teacher!!

 

[Finx]

Who doesn't =P

 

[minijumbuk]

I hope i get a brilliant chemistry teacher!!

... =\

You should really be hoping you get a brilliant teacher for every single subject, not just chemistry =O