[AWK]

I prefer solution of this kind of stoichiometric problems through mass fraction that can be treated as unitless value.
mass fraction of Al in Al₂O₃ is 2Al/Al₂O₃=54/102
Hence mass of Al in 5 tonnes Al₂O₃ (5 treated as an exact number)  is 0.529×5 tonnes with final 2 significant digits.

[jamesbrown]

We put in 50ml of sodium thiosulfate in and we put 5ml of hydrochloric acid in.

This is the equation:
HCl + sodium thiosulfate   sodium chloride + sulfur dioxide + sulfur + water.
2HCl(aq)  +  Na2S2O3(aq)           2NaCl(aq)    +      SO2(g)    +   S(s)  +  H2O(l)

I was given this as an extension and have no idea how to do this as we haven't gone over anything to do with theoretical mass. So i'm really stuck, so if someone could work it out for me and explain it I would be hugely appreciative of it.

Thanks 

[mikasaur]

Is that all there is to the prompt? Was this a lab or part of a problem set?

If you give us the exact wording of the question we can help out a little more.

[jamesbrown]

We performed the test in a lab and here are a few graph that might be helpful.

[mikasaur]

It's still very hard to help you with the information given.

I'm not sure what you mean by an "extension". Was this a question that was done after your lab? What exactly was the lab?

[jamesbrown]

Experiment:
We tested how quickly 50ml of Sodium thiosulphate solution reacted with 5ml of hydrochloric acid at different temperatures to test how temperatures affect rate of reaction.
Method:
Prepare 50 ml of thiosulphate and 5ml of HCL, stopwatch and paper with a clear X on it(and a conical flash to mix solutions in)
Then heat water in a beaker until the required temperatures, when this is done put the conical flask inside the beaker (using it as a water bath) place it on the paper then mix both solutions.
Then time how long it takes for the thiosulphate and HCl take to react by waiting until the cross on the paper is unreadable through the solution. (HCL and Thiosulphate make an opaque product)

[Borek]

Still not clear what is the "extension" you talk about.

Prepare 50 ml of thiosulphate and 5ml of HCL

You were not told anything about concentrations?

[jamesbrown]

Extension means an extra question

concentrations:
Sodium thiosulphate 0.15
Hydrochloric acid 2

[mikasaur]

concentrations:
Sodium thiosulphate 0.15
Hydrochloric acid 2

Units, dude!! Numbers without units are meaningless.

[jamesbrown]

concentrations:
Sodium thiosulphate 0.15
Hydrochloric acid 2

Units, dude!! Numbers without units are meaningless.

moles/dm³

[mikasaur]

Cool. There ya go.

So there was no prompt for your extension? You just got a piece of paper that said "find the theoretical mass of sulphur"? I feel like we're missing something here.

[AWK]

Seems to be a stoichiometric problem with a limiting reagent.

[Burner]

So there was no prompt for your extension? You just got a piece of paper that said "find the theoretical mass of sulphur"? I feel like we're missing something here.

I think the paper maybe asking you to calculate the percentage yield based on the theoretical mass and the actual mass of sulphur obtained, as that's what our pubilc exam papers(HKDSE) always do.

Anyway, I think that calculating theoretical mass is simliar to ordinary mole calculations involving mass, though in this lab we may need to find out the limiting reagent in the reaction and use that number of moles of that limiting reagent to do calculations.

[Borek]

I suspected the type of problem AWK named, which is why I asked if you are given concentrations. If so, the question to solve is most likely just "What is the theoretical mass of sulfur produced when you mix 50 mL of 0.15 M sodium thiosulfate with 5 mL of 2 M HCl solution".

[jamesbrown]

So do you guys know how to do it or not?

Thank you for this by the way.