Chemistry 3/4 2013 Thread

[hardworker]

If Carbonic acid reacts with a base of sodium carbonate which is the one in excess. 

H2CO3+Na2CO3 ARROW Na2CO3+H20+CO2

[teletubbies_95]

Hey guyss! Great questions everyone! and wishing you the best of luck for all your sacs!

I have a question which is attached?
How do you determine the mole ratio between MgSO4.7H20 and MgNH4PO4.6H20?


Thanks !

[justsoundslikeaworn-outcliche]

Thanks for the reply

Got a few other questions: calc the mass of anhydrous sodium carbonate required to make 250ml of a 0.1M solution.
Don't quite know how to approach that one^

[Conic]

Thanks for the reply

Got a few other questions: calc the mass of anhydrous sodium carbonate required to make 250ml of a 0.1M solution.
Don't quite know how to approach that one^

250mL = 0.25L

[justsoundslikeaworn-outcliche]

250mL = 0.25L

Wow that was a quick reply! It makes sense now I realised I'd written one
Of the numbers wrong! :/

[justsoundslikeaworn-outcliche]

Last question and I've completely finished this sheet! But i need help : Determine the number of mol of chloride ions in a 10gram sample of HCL ! I use n=m/mr right? but it still not working out :S
Cheers in advance

[Jeggz]

Is the answer 0.33?

[justsoundslikeaworn-outcliche]

how'd you get that??

[Jeggz]

how'd you get that??

Well you're thoughts were perfectly correct 
You know that mass (HCl) = 10 grams
Hence the n(HCl) = 12/Mr , the Molar mass of HCL is 35.5+1 = 36.5
Hence, n(Hcl) = 0.33 and the Moles of Hydrogen = Moles of Cl due to 1:1 ratio

[justsoundslikeaworn-outcliche]

Well you're thoughts were perfectly correct 
You know that mass (HCl) = 10 grams
Hence the n(HCl) = 12/Mr , the Molar mass of HCL is 35.5+1 = 36.5
Hence, n(Hcl) = 0.33 and the Moles of Hydrogen = Moles of Cl due to 1:1 ratio

yeah that works but where'd you get the 12 from?
thanks btw

[Jeggz]

yeah that works but where'd you get the 12 from?
thanks btw

OMG SORRY! haha, I meant 10/Mr! 

[justsoundslikeaworn-outcliche]

haha thats okay!wait so the mol for hcl is the same for the chloride ions in it?

[Jeggz]

haha thats okay!wait so the mol for hcl is the same for the chloride ions in it?

Yup exactly! It's because of the 1:1 ratio between Hydrogen and Chloride. If that makes sense!
For example if it was like H2SO4, then the mole ratio between Hydogen and Sulfate is 2:1 and hence the mole of Sulfate ions would be half the number of Hydrogen mole.

[academicbulimia]

hey i'd just like some help on a few chem questions i'm having trouble with. We did a practice sac today with the analysis of brick cleaner in prep for the fertilizer analysis sac next week, we used a brick cleaner that was 32% hcl, got 5ml of this brick cleaner and  diluted this with distilled water, and then used a 20ml sample of this and used  and 0.1 AgNO3 as the titre to be titred into the brick cleaner sample, a precipitate formed we then filtered this with a vacuum pump, and lastly we dried it overnight to find the end product of a sample of 2.945g AgCl.

how would i determine the no of mol, of chloride ions in the undiluted sample of brick cleaner?

and the mass of hcl in the original sample?
thanks in advance!!!

[academicbulimia]

hate to be a drag but i kinda need urgent help because these questions^ are due tomorrow :s