Chem 2/5 Lab # 423 – Empirical Formula

PostLab Questions

 

  1. What is the law of definite proportions?

  2. How can you find the empirical formula of a compound from mass measurements?

  3. What are the hazards associated with magnesium and magnesium oxide?

  4. 4.When a compound is formed by heating reactants in a crucible, why is it necessary to cool the crucible and products before reweighing?

  5. The formula of a compound of lead (Pb) and sulfur (S) was determined using the method of mass measurements.

A sample of Pb was weighed into a crucible and covered with finely powdered S. the crucible was covered and heated to allow the Pb and S to react. Additional heating burned off all unreacted S. The crucible was then cooled and weighed. The following data were collected.

Mass of crucible and cover, g 27.889

Mass of crucible, cover and Pb, g 32.025

Mass of crucible, cover and compound formed, g 32.666

    1. Calculate the mass of Pb reacted

    2. Calculate the mass of compound that formed

    3. Calculate the mass of S reacted

    4. Calculate the moles of Pb reacted

    5. Calculate the number of moles of S reacted

    6. Find the simplest whole-number ratio of the number of moles of Pb to the number of moles of S in the compound formed.

    7. Write the empirical formula for the compound formed.