Chemistry content or calculations? (1 Viewer)

[Georgina168]

So I feel like i've cover as much content as i can. But the calculations i've pretty much given up on. I can do the volumes of gas and pH and heat of combustions. Should I be able to pull in over 50% in this?

 

[MagnificentOne]

Which types of calculations are you struggling with?

 

[Georgina168]

Which types of calculations are you struggling with?

Equilibriums, percentage of sulphate in fertilizer, how to get the change in heat that caused the molar heat of combustion, titration calcs, esterfication calcs. Love chem

 

[jamesfirst]

what's esterification calculation ??


I am kinda struggling with the ppm calculation. Im so gonna skip it when it comes outl

 

[Effekt]

I wanna hijack this thread, i need help with calculations too.

Here is an example of the ones i can't do

You have a bottle of H2SO4 and the label has been dissolved away. You titrate it against a 0.01M solution of KOH and use 46.7mL of KOH in the titration. You use a 25mL aliquot of the acid so calculate the concentration that should be on the bottle and it’s pH.

 

[Tsunayoshi]

I am kinda struggling with the ppm calculation.

This. I hate doing them...

Also esterification calculations?? ermm..determining the mass of the ester produced?? never heard of them =\

 

[Georgina168]

This. I hate doing them...

Also esterification calculations?? ermm..determining the mass of the ester produced?? never heard of them =\

I just remember doing a calculation after we did the ester prac.. And our class struggled with it so bad and no one understood what to do.

 

[khorne]

I wanna hijack this thread, i need help with calculations too.

Here is an example of the ones i can't do

You have a bottle of H2SO4 and the label has been dissolved away. You titrate it against a 0.01M solution of KOH and use 46.7mL of KOH in the titration. You use a 25mL aliquot of the acid so calculate the concentration that should be on the bottle and it’s pH.

titration calcs: VaCa/a = VbCb/b where Va is volume of acid used, Ca is molarity and a is coefficient of the acid term in the equation. You have all the data but Ca, so you can find it easily

 

[khorne]

I just remember doing a calculation after we did the ester prac.. And our class struggled with it so bad and no one understood what to do.

Either classic hsc troll, or forgetting. There's no ester calculation

 

[Midnight_Lotus]

I've found that after completing all the calculation questions from 2003 - 2010 (and still don't feel confident with them) the percentage of marks associated with calculations is around 10-18%. So if you don't do any calculations at all you still have the potential of getting a band 6

 

[khorne]

Equilibriums, percentage of sulphate in fertilizer, how to get the change in heat that caused the molar heat of combustion, titration calcs, esterfication calcs. Love chem

For sulphate, it's easy. You need to find percentage, so what you can do is:

n(baso4) = filtrate weight/ M(baSo4)
n(SO4) = n(baso4)
from that calculate weight of SO4 and then percentage by dividing weights and multiplying by 100%

Otherwise:
weight of filtrate * M(so4)/M(baso4) = weight of so4, and do it that way.

 

[Tsunayoshi]

@ Midnight Lotus,

seriously..that made my day.