[kandyfloss]

i've attached an image file with the question
i just need help with part (c) of the question.
thank you

[Schrödinger]

Well, if you have found out the limiting reagent and the number of moles of it present, then use the chemical equation to work out the ratio in which the reactants should react, and hence find out how much of the excess reagent has actually been used. Use this data to find out how much of the original amount of the excess reagent is left over.

Hope this helps.

[kandyfloss]

i don't understand..can me show me how to work it out using the values i found out?
here's what i've got
moles of CCl4 - 0.325 moles
Moles of SbF3 0.279 moles
therefore SbF3 is the limiting reagent (ami right so far?)
No using the ratios in the equation i found the mass of Freon-12 which is 101.4 g
please show me how to do the third part?

[Borek]

As they say - left hand to the right ear, but OK. Numbers of moles that you have shown are already after dividing by the stoichiometric coefficients, so direct comparison works.

How many moles of CCl₄ reacted?

[kandyfloss]

Oh wait,there's a mistake in my values
Here's what i did now - I found the amount of substance
CCl4 - 150/153.80 = 0.9752 moles
SbF3 - 100/178.75 = 0.5594 moles
Now ratio of moles is 1.74 : 1 (dividing by the smallest)
There are 3 molecules of CCl4 and 2 of SbF3
Now diving this ratio by these value we get the no. of moles that reacted (i think)
which is 0.58 (CCl4) and 0.50 (SbF3)
Thats all i did so far..I dont understand the exces reagents part.

[Borek]

No idea what you did this time, juggling numbers is not a way of getting reasonable answers. You were OK previously.

Assuming SbF₃ is a limiting reagent, and all reacted, how many moles of CCl₄ reacted?

[kandyfloss]

But this is the way my book has juggled with number as well.
Can you do the calculations and show? Because i think mine is messed up,and i don't know how to find how many moles of CCl4 reacted

[Borek]

But this is the way my book has juggled with number as well.

Either the book is not worth anything or you don't understand what they did. Ratio of moles of substances mixed (1.74) - if they are not mixed in stoichiometric amounts - can't be used to calculate amount of products.

Can you do the calculations and show? Because i think mine is messed up,and i don't know how to find how many moles of CCl4 reacted

You know number of moles of SbF₃, you know reaction equation, where is the problem? Forget about limiting reagents, just calculate stoichiometric amount of CCl₄.