Calculating Percent Yield

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Given Questions: 155.8 Kg of SiO2 reacts with 78.3 Kg of Carbon to produce 66.1 Kg of silicon. What is the percent yield of the reaction?

1. The first step is to convert your given masses into moles. This way, you can see which reactant is in excess and which one is limiting. A good flow of thought would be: kilograms of SiO2/Carbon→ grams SiO2/Carbon→moles SiO2/Carbon.

2. Repeat this step for the carbon reactant.

 3. By comparison, we can tell that the carbon reactant is in excess, which means that the SiO2 reactant is limiting. Because of this, we’ll use the amount of SiO2 to find our percent yield. There’s only so much SiO2 that can react with the carbon.

4. You can now calculate the actual and theoretical yields. The theoretical yield is larger than the actual yield because it does not have physical interactions like loss of energy to the environment and friction to interfere with the reaction.

5. Now compare your two values of actual and theoretical. The formula for percent mass is [(Actual yield)/(Theoretical yield)]*100%. Our final answer for this question is the percent yield of the reaction is 90.8% We can interpret this as 90.8% of the SiO2 reacting will produce solid silicon.

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