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# Stoichiometry Example Problems

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1. Calculate the emperical formula for a chemical compound which gives the following analysis 12.6 percent lithium 29.2 percent sulfur and 58.2 percent oxygen?

2. The action of bacteria on meat and fish produces a poisonous compound called cadaverine. It is 58.77 percent carbon, 13.81 percent hydrogen, 27.40 percent nitrogen. Its molecular weight is 102.2g/mol determine the molecular formula.

3. Calculate the empirical formula for a chemical compound which gives the following 65.2 g scandium and 34.8 g oxygen.

4. The compound k2sio2. h2o is a hydrated crystal. An empty evaporating dish was weighed and found to have a mass of 61.57g. The hydrated crystal was added and the new mass was 63.71g the evaporating dish with the sample was heated to remove water after heating was found to have a mass of 62.61g What is the correct formula for this hydrating crystal (mw for k2sio3 =154 g/mol and the mw for h20 =18g/mol).

5. A 4 g sammple of the hydrated crystal ba(oh2).h20 is heated until all the water is removed. The remaining solid weighs 2.17g Calculate the formula of the hydrated crystal

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#### Solution Preview

1)
Assume 100 g compound
mol Li = 12.6/6.941 =1.822
mol O = 29.2/16 = 1.825
the ration is around 1:1
empirical formula = LiO

2)
Assume 100 g compound
mol C =58.77/12 = 4.897
mol H = 13.81/1 = 13.81
mol N = 27.40/14 = 1.957
divide all by 1.957 = C2.5 H7 N1
multiply all by 2 = C5 H14 N2
empirical formula = C5H14N2 ---> which has a weight of 5(12)+14+(2(14) = 102 which equal with the ...

#### Solution Summary

This solution provides steps necessary to determine the answer for each of the stoichiometry problems.

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