Baaic Experiments
in Chemistry experimental yield Percent yield = x 100%
theoretical yield
The theoretical yield is the calculated maximum amount of product which
might be obtained under IDEAL conditions from the starting MATERIALS. In an
experiment, the theoretical yield is seldom, if ever, reached. In this experiment,
the theoretical yield will be the maximum amount of potash alum which might
be obtained from the specified amounts of starting materials.
In calculating the theoretical yield, you should first calculate the moles of each
reactant and then find the limiting reagent. The limiting reagent determines the.
theoretical yield of the product. The reactant that is consumed completely in Ii "'
chemical reaction is called the limiting reagent.
g of Al,(SO4),, 18H,O taken' No. of moles of A12(S04)3. 1 8H20 taken = ----
gram molecular weight
- - 5'0 - 0.0075 MOL 666.2
No. of moles of K2S04 taken = g of K2S04 -- . taken
gram inolecular weight
- - -- 'SO - 0.0085 mol
174.25
Since, aluminium sulphate and potassium sulphate react in equimolar ratio, the
former is the limiting reagent because it is present in less amount. Thus, the
theoretical yield of potash alum is 0.0075 mol. The theoretical yield in gram
can be calculated by multiplying the yield in rnol by the molecular weight.
Theoretical yield = 0.0075 x 948.26 = 7.1 g
experimental yield Percent yield = x ! 00% 7.1
10.7 RESULT
The percent yield of potash alum = %
10.8 SUMMARY
In this experiment, you have performed the following:
prepared potash alum,
crystallized potash alum, and
calculated the percent yield of potash alum.