Question

3. A student makes a solution for analysis by mixing 5.172 grams of Cu_{2SO4 into 500 grams of water. The density of water at the temperature of the lab at the time the solution was made is 0.9926 g/mL. Calculate the molarity, molality, mole fraction, and mass percent of the copper 1 sulfate. Show all work.}

_{1. The presence of a dirty fingerprint on the cuvette during measurement of the sample solution resulted in the absorbance being reported incorrectly. Do you think the number reported was too high or too low? Explain why.}

_{2. List the important sources of error in this experiment and what effect each would have on the results. Discuss in particular any errors that you may have made include at least 3 ( with specific implications) for full credit.}

_{( PLEASE SHOW ALL WORKINGS AND SOLUTIONS)}

Answer 1

Question 3 has 4 parts.I will calculate all 4 quantities. Remaining part needs to be asked as different question.

Molar mass of Cu2SO4 = 223 g/mol
Molar mass of H2O =18 g/mol

Mass of Cu2SO4 =5.172 g
Mass of water = 500 g or 0.5 Kg

number of moles of Cu2SO4 = mass /molar mass = 5.172/223 =0.0232 mol
number of moles of water = mass /molar mass = 500/18 =27.8 mol

Volume of water = mass / density = 500 /0.9926 = 503.7 mL = 0.5037 L

Molairty = number of moles of Cu2SO4 / volume in L
                   = 0.0232 / 0.5037
                   = 0.046 M

Molality = number of moles of Cu2SO4 / mass if water in Kg
                   = 0.0232/ 0.5
                   = 0.0464 m

mass percent of Cu2SO4 =mass of Cu2SO4 *100/ total mass
                                                = 5.172*100 / (5.172+500)
                                                = 1.02 %

Mole fraction of Cu2SO4 = moles of Cu2SO4 / total moles
                                                   = 0.0232 / (0.0232+27.8)
                                                    = 0.00083