# Precipitating Lead Chromate on a Small Scale

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Purpose The purpose of this experiment is to use our knowledge from previous experiments to determine the theoretical, actual, and percent yields of the lead chromate from the reaction of solutions of potassium chromate and lead nitrate (Lab Guide pg. 83). Question or Problem The question that was proposed for investigation was: Can the theoretical, actual, and percent yields be determined accurately (Lab Guide pg. 83)? Background Discussion For this experiment we have to use physical methods to separate the reaction mixture from the liquid. The physical methods that were used are filtration and evaporation. Filtration is the separation of a solid from a liquid by passing the liquid through a porous material, such as filter paper. Evaporation is when you place the residue and the damp filter paper into a drying oven to draw moisture from it by heating it and leaving only the dry solid portion behind (Lab Guide pg. 33.). Sample Calculations In this experiment there were eight different equations used and they were, molecular equation, total ionic equation, net ionic equation, calculating the number of moles, calculating the theoretical yield and limiting reagent, calculating the mass of〖PbCrO〗_4, calculating actual yield, calculating percent yield (Lab Guide pg.83-85). Molecular Equation:K_2 CrO_4 (aq)+Pb(〖NO〗_(3)) /2→〖PbCrO〗_4 (s)+2KNO_3 (aq) Total Ionic Equation: 〖2K〗^+ (aq)+〖CrO〗_4^(2-) (aq)+〖Pb〗^(2+) (aq)+ 〖2NO〗_3 (aq)→〖PbCrO〗_4 (s)+ 〖2K〗^+ (aq)+〖2NO〗_3^- Net Ionic Equation: 〖Pb〗^(2+) (aq)+〖CrO〗_4^(2-) (aq)→〖PbCrO〗_4 Calculating the Number of Moles: Number of moles of〖 K_2 CrO〗_4, mol = (4.0 ×〖10〗^(-2) mol L^(-1))(5.0×〖10〗^(-2) L)= 2.0×〖10〗^(-3) mol Number of moles〖Pb(NO〗_3)/2, mol = (8.0 ×〖10〗^(-2) mol ... ... middle of paper ... ...form 〖PbCrO〗_4 and then process it through a filter. After filtering the 〖PbCrO〗_4 I had to dry the 〖PbCrO〗_4 residue in the drying oven for 30 minutes at 80℃. Then let it cool for 5 minutes and weigh it and finally make a few calculations to obtain the theoretical, actual, and percent yields of 〖PbCrO〗_4. I was able to fulfill the experiment because I obtained all the answers to the equations in an accurate amount. I believe this experiment was a success due to my hypothesis of, If physical methods are used to separate 〖 PbCrO〗_4 precipitate from the reaction mixture then I can successfully calculate the theoretical, actual, and percent yields, being correct. Works Cited Neidig, H. A., and J. N. Spencer. "Precipitating Lead Chromate on a Small Scale." General Chemistry For Engineering And Science. Mason: Cengage Learning, 2012. 83-90. Print. Signature Lab Ser.