Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

Empirical and Molecular Formula Practice

Empirical Formula Practice:

Resolve the following exercises in your spiral notebook after your notes. Show clearly the title. Copy the questions and answer. Highlight the questions and square the answers.

  1. . A compound is found to contain 26.53% potassium, 35.37% chromium, and the remainder oxygen.
    Find its empirical formula. K2Cr2O7
  2. A 60.00 g sample of tetraethyl-lead, a gasoline additive, is found to contain 38.45 g lead, 17.83 g
    carbon, and 3.72 g hydrogen. Find its empirical formula.  PbC8H20
  3. A 170.00 g sample of an unidentified compound contains 48.27 g sodium, 54.57 g chromium, and
    67.16 g oxygen. Find the empirical formula. Na2CrO4
  4. Determine the molecular formula of the compound with an empirical formula of CH and a formula
    mass of 78. C6H6
  5. One of the compounds present in Asbestos is Chrysotile, a compound that has Mg, Si, H and O in its formula. 7.770 g of Chrysotile is forund to have 2.160 g of Mg, 1.680 g of Si, and 0.090 g of H. The molar mass of Chrysotile is 518 g/mol. Calculate the EF and the MF of the compound. Mg3Si2H3O8 (empirical formula), Mg6Si4H6O16 (molecular formula)