Lab Report-3-Stoichiometry Calculations

Stoichiometry Calculations Exp. No. 3 I.  Purpose The purpose of this lab simulation was to learn about the composition of compounds. The lab will teach how to use calculations such as molecular weight, mass and moles, product yield and balanced equations to help identify an unknown substance. II.  Experimental Method There is a 500g container of a substance that has Chloride on the label. The type of Chloride needs to be identified. In order to discover what the unknown substance is, it mixed with a solution of Silver Nitrate (AgCO3). Three compounds, BeCl2, MgCl2, and CaCl2 contain the formula (x)Cl2. 3.0456 grams of the unknown substance was put on a plate with a spatula and weighed. The lab journal has the equation f m(g)=XCl2+2AgNO3- >X9NO3)2+2AgCl. The unknown substance is shown XCl2 in yellow. The amount measured 3.0456g is entered. There are different tabs in the journal to for each of the substances BeCl2, MgCl2, and CaCl2. Clicking on each tab allows to input how many moles of each as well as the reaction of each with AgNO3. A 200 mL conical flask was placed on a heating plate. The 3.0456g of the unknown substance XCl was transferred to the conical flask. A measuring cylinder of 50mL demineralized water was added to the conical flask. A magnetic stirrer was used, the heating plate turned on so the unknown substance and the demineralized water can dissolve. To get a reaction from the Cl, 2 times as much AgNO3 is added. H20 X2 + NO-3 N + AgCl A measuring cylinder was used to transfer 100 mL of AgNO3 solution into a conical flask. The AgNO3 solution turned cloudy. Filter papers were used to dry the solution, and then it was weighted to determine how much chloride was in the solution. Suction filtration was used. A rubber cone was placed on the opening of the suction flask, and filter paper was placed inside. Water was added to ensure the filter was securely in place. The filter cake was placed on a watch glass in an oven to dry it. This weight is added to the journal. By using the formulas to calculate all of the substances, it is concluded that this unknown must be MgCl2. III.  Raw Data and Calculations An example of how to use analytical balance was given by using corn kernels. The average mass of one corn kernel is .282 g. If there are 100 corn kernels the result would be 28.2 g. The formula would be: .282g x 100 = 28.2g. This theory can be applied to Avogadro’s number and molecular weights to find the mole of a substance. Molecular weight: M(g/mol) = m(g) / n(mol)

Grams: m(g) = n(mol) x M(g/mol) Moles of substance: n(mol) = m(g) / M(g/mol) These formulas were used to calculate the moles of all the substances to determine our unknown. X = Be BeCl2 + 2 AgNO3 -  Be(NO3)2 + 2 AgCl m(g) = m=M*n 3.0456 10.951 Mw (g/mol) = 79.718 143.42 N (MOL) = n=m/M 0.038 0.076 0.076 X = Mg MgCl2 + 2 AgNO3 -  Mg(NO3)2 + 2 AgCl m(g) = m=M*n 3.0456 9.169 Mw (g/mol) = 95.211 143.42 N (MOL) = n=m/M 0.032 0.064 0.064 X = Ca MgCl2 + 2 AgNO3 -  Ca(NO3)2 + 2 AgCl m(g) = m=M*n 3.0456 7.866 Mw (g/mol) = 110.98 143.32 N (MOL) = n=m/M 0.027 0.055 0.055 IV.  Results XCl2 + 2 AgNO3 -  X(NO3)2(aq)+ 2 AgCl(s) m(g) = 3.0456 8.5341 Compound is MgCl2 Percentage yield Y=(E/T)*100% 93.075 The unknown substance was identified as MgCl2. A 93% yield of MgCl2 was obtained during this lab experiment. V.  Conclusion