[Shimu]

reaction:
2 C6H5CHO + CH3COCH3 = C6H5CHCHOCHC6H5 + 2 H2O

Benzaldehyde 2.6 g   MW=106.1
Acetone .9 mL          MW=58.1

the weight of dibenzylideneacetone found after reaction was 1.94g.

How can I get the %yield?

[Schrödinger]

This might help : http://www.800mainstreet.com/6/0006-007-percent-yield.html

[Shimu]

thank you.

but for the following reaction:
C + O2 = CO2

O2 is not used, C is used from both the 2 reactants.

on my problem which one can I use to calculate the yield benzaldehyde or acetone?

[AWK]

Which one is a limiting reagent?

[Shimu]

I don't know. How can measure that it is limiting reagent?

[Borek]

Find acetone density, calculate its mass.

[helenn]

You need to calculate the number of moles of each reagent and see which is the limiting reagent from that.

[AC Prabakar]

This might help : http://www.800mainstreet.com/6/0006-007-percent-yield.html

This is very good link and you can try this....

[AC Prabakar]

I don't know. How can measure that it is limiting reagent?

Generally when we are calculating the yield it should be with respect to one of the reagent(if we are taking any reagent higher than actually require).
In this case benzaldehyde (0.02450 mol,1.0eq.)used and acetone(0.012160 mol,0.49 eq.)which is theoretically required.
Hence we can calculate with respect to any of the reagent!!!!!

[ardbeg]

If the ratio is 1:0.49 then acetone is the limiting reagent so you have to calculate the yield from acetone to be accurate.

[Agathiyar]

First calculate the moles or mmoles of the two starting materials and find out the limiting substance. In your case it is acetone and hence yield would be based on howmuch moles you are getting from x moles of acetone.

[swamik]

reaction:
2 C6H5CHO + CH3COCH3 = C6H5CHCHOCHC6H5 + 2 H2O

Benzaldehyde 2.6 g   MW=106.1
Acetone .9 mL          MW=58.1

the weight of dibenzylideneacetone found after reaction was 1.94g.

How can I get the %yield?

Hi,

2 C6H5CHO(2*106) + CH3COCH3(58) = C6H5CHCHOCHC6H5(234) + 2 H2O(2*18)
         212gm         +       58gm        =             234gm              +        36gm


a) Therotical yield
                             = 2.6x234/212 =2.86gm (100% yield)

b) Practical yield
                             = 1.94x100/2.86 =67.8%
                               

[Agathiyar]

In your case 1:0.49 ratio does not make big difference, for equimolar it should be 1:0.5.
The yield is 68.1%.

[Shimu]

Thanks every one. I got my answer.