Lab exercise 7.5 1 answers

Final Report

Exercise 1

CHEM 181 DL1 Stoichiometry of a Precipitat ion Reaction

My percent yield was 86 percent. It was not the optimal 100 percent, but it was on the higher range. It could be possible that I could have had a higher percent yield had the scale not have gone only to the tenth place. My theoretical yield was 0.68 g. But because the scaleonly went to the tenths place I cannot speak with certainty that the weight of my product was only 0.6 g. It's possible that it could have been 0.68 g but I will never know that. There

1. Given that a theoretical yield for isolating Calcium Carbonate in this experiment would be 100%. From that information and based on the results you obtained in this experiment, describe your success in the recovery of calcium carbonate and suggest two possible sources of error that would have caused you to not obtain 100% yield.

Excess product of CaCO3 would be produced because there wouldn't be enough CaCl2 to react with Na2CO3. The purpose of stoichiometric quantities is to know the correct amount or close to the correct amount of each reactant in order to produce a product that is close to the theoretical amount and therefore have a higher percent yield.

2. What impact would adding twice as much Na CO than required for stoichiometric quantit ies have on the quantity of product produced?

2 3

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Data Table 1: Stoichiometry Values

7.5gCaCl2•9H2O x(1molCaCl2•9H2O/273.16gCaCl2•9H2O)x(1molCaCl2/1molCaCl2•9H2

3. Determine the quantity (g) of pure CaCl in 7.5 g of CaCl •9H O. Show your work.2 2 2

4g MgSO4•7H2O x(1mol MgSO4•7H2O/246.51g MgSO4•7H2O)x(1mol MgSO4/1mol MgSO4•H2

4. Determine the quantity (g) of pure MgSO in 2.4 g of MgSO •7H O. Show your work.4 4 2

According to the background, our established total mass of the reactants should equal the total mass of our on hand products. Thus we should expect a slightly smaller amount of product since in practical experimentation a system is seldom completely closed. The conservation of mass could be checked in our experiment by weighing the reactants and weighing our product. The total mass of the reactants should be slightly larger than the weight of the product.

5. Conservation of mass was discussed in the background. Describe how conservation of mass (actual, not theoretical) could be checked in the experiment performed.

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Initial: CaCl •2H O (g)

Initial: CaCl •2H O (mol)

Initial: CaCl (mol)

Initial: Na CO (mol)

Initial: Na CO (g)

Theoretical: CaCO (g)

Mass of Filter paper (g)

Mass of Filter Paper + CaCO (g)

Actual: CaCO (g)

% Yield:

2 2 1.0 g

2 2 0.0068 mol

2 0.0068 mol

2 3 0.0068 mol

2 3 0.8 g

3 0.68g

0.9 g

3 1.5 g

3 0.6 g

86%