### Stoichiometry of a Precipitation Reaction

|| || Data Tables: Step 3: Show the calculation of the needed amount of Na2CO3 Convert 1. 0g of CaCl2-. 2H2O to moles of CaCl2-. 2H2O 1. 0g x 1 mole CaCl2-. 2H2O 147. 0 g CaCl2-. 2H2O = 0. 00680 moles CaCl2-. 2H2O The mole ratio is 1:1 Hence if we have 0. 00680 moles of CaCl2-. 2H2O we will as well need 0. 00680 moles of Na-2CO3 Convert moles of Na-2CO3 to grams of Na2CO3 = 0. 00680 moles Na-2CO3 x 105. 99g Na-2CO3 1 mole Na-2CO3 = 0. 72g This means that we need 0. 72g of Na-2CO3 to fully react with 1g of CaCl2-. H2O Step 4: Mass of weighing dish_0. 7___g Mass of weighing dish and Na2CO3__1. 4__g Net mass of the Na2CO3 __0. 7__g Step 6: Mass of filter paper __0. 7__g Step 10: Mass of filter paper and dry calcium carbonate__1. 2__g Net mass of the dry calcium carbonate_0. 5___g (This is the actual yield) Step 11: Show the calculation of the theoretical yield of calcium carbonate. The mole ration between CaCl2-. 2H2O and CaCO3 is 1:1 that means that if we have 0. 00680 moles of CaCl2-. 2H2O we will get 0. 00680 moles CaCO3

Convert the moles of CaCO3 to grams of CaCO3 = 0. 00680 moles CaCO3 x 100 g CaCO3 1 mole CaCO3 = 0. 68g CaCO3 Show the calculation of the percent yield. = Actual yield/Theoretical yield x 100 = 0. 5/0. 68 x 100 = 73. 5% Conclusion: The objective of the experiment is to predict the amount of product produced in a precipitation reaction using stoichiometry. Secondly, the experiment accurately measures the reactants and products of a reaction. Also, the experiment is to determine actual yield vs. theoretical yield and to calculate the percent yield.

For example in this experiment, we were able to predict that we need 0. 72g of Na-2CO3 to fully react with 1g of CaCl2-. 2H2O. Another example is that, we calculate the amount of theoretical yield of Calcium Carbonate to be 0. 68g and the percentage yield to be 73. 5%. The scientific principles involved here was that when two or more soluble substances in separate solutions are mixed together to form an insoluble compound they settles of a combined solution as a solid. The solid insoluble compound is called a precipitate.

For example in this experiment, we combined sodium carbonate and calcium chloride dehydrates to produce a precipitate of calcium carbonate. The formula mathematically is Na2CO3(aq) + CaCl2. 2H2– = CaCO3(s) + 2NaCl(aq) + 2H2O. Sources of Error and ways to minimize them: There may still be some solid particles in the beaker thereby we will not be able to get the correct mass (quantity) of the Calcium Carbonate. To minimize the error we should use an instrument that can be able to scoop out the entire solid from the beaker.

Also if the water in the Calcium Carbonate is not properly dried, the net mass of the Calcium Carbonate can be extremely high. To solve this we must make sure the Calcium Carbonate is well dried. Error of approximation: the molar mass if not well approximated, can lead to an error in the calculation. To minimize this error the instruction should indicate how many decimal point or how significant figure to approximate to. I am highly impressed with the experiment.