Questions in chemistry!

[mars_mhel]

HI! I don't know how to answer this question about stoichiomestry! any ideas?

 

The potassium salt of benzoic acid, potassium benzoate, KC₇H₅O₂, can be made by the action of potassium permanganate on toluene, C₇H₈.

C₇H₈ + 2 KMnO₄ --> 2MnO₂ + KOH + H₂O

 

If the yield of potassium benzoate cannot be realistically be expected to be more than 71%, what is the minimum number of grams of toluene needed to achieve this yield while producing 11.5 g of potassium benzoate?

 

[YT2095]

so in boiled down terms: 11.5 is 71% of (x)

 

100/71= (ans)

(ans)x11.5= 16.2

 

I`m lousey at maths, but I work it out to 16.2 grams needed.

 

wait until one of the maths guys gets here before taking that answer as gospel though!

[mezarashi]

C7H8 + 2 KMnO4 --> 2MnO2 + KOH + H2O

 

Firstly, your equation there is obviously not correct.

 

C7H8 + 2KMnO4 → KC7H5O2 + 2MnO2 + KOH + H2O

 

Working on the correct equation then, you can see that for each mole of toluene, you get one mole of potassium benzoate. However it says that you cannot expect more than a 71 percent yield. If my interpretation is correct, we can just alter this to be: for every mole of toluene, you can expect to get 0.71 moles of potatssium benzoate.

 

From there, work using stoichiometry to find the molar mass of the two and solve ^^

[YT2095]

however oddly, when working organic chem, it`s rare that you`ll ever get 100% yeild from a process. the 71% doesn`t surprise me (it`s not Brilliant, but is don`t surprise).

[lan418]

Nothing ever yields a 100%.

[mars_mhel]

HI! I don't know how to answer this question about stoichiomestry! any ideas?

 

The potassium salt of benzoic acid, potassium benzoate, KC₇H₅O₂, can be made by the action of potassium permanganate on toluene, C₇H₈.

C₇H₈ + 2 KMnO₄ --> KC₇H₅O₂ + 2MnO₂ + KOH + H₂O

 

If the yield of potassium benzoate cannot be realistically be expected to be more than 71%, what is the minimum number of grams of toluene needed to achieve this yield while producing 11.5 g of potassium benzoate?