Honors Chemistry Chapter 3.3-3.5 Pre-Test #3Name______

Mr. Citta – 3-19-15Date______

Mole-Liter Conversions –Empirical-molecular Formulas

Avogadro’s number = 1 mole = ______molecules/atoms or formula units

Molar Volume of a gas = 1 mole = ______liters____ liter = ______milliliters

Standard Temperature = ______0C ______K ____moles = ______millimoles

Standard Pressure =_____atm ______mmHg ______grams = ______grams (micrograms)

  1. Complete the following problems.Remember to Show all work for every single calculationor no credit will be given. Use dimensional analysis!!
  1. How many carbon atoms are found in 505 milliliters of butane (C4H10) at STP conditions?

a =

  1. How many milliliters do 25.9 milligrams of butane (C4H10) occupy at STP conditions?

a =

  1. How many hydrogen atoms are found in 33.5 milligrams of butane (C4H10)?

a =

  1. How many micrograms (g) are in 458 milliliters of hydrogen gas at STP conditions?

a =

  1. How many liters are in 3.50 millimoles (mn) of CO2 at STP?

a =

  1. How many millimoles are in 29.4 liters of CO2 at STP?

a =

  1. What is the molar mass of a gas if 789 milligrams (mg) of the gas are found to occupy 20.5 milliliters at STP conditions?

Empirical/Molecular Formula (Show all work!!!) answers are provided.

  1. Methyl benzoate, a compound used in the manufacture of perfumes is found to contain 70.57 % carbon, 5.93 % hydrogen and 23.49 % oxygen. What is the empirical formula of this substance? a = C4H4O.
  1. Mesitylene, a hydrocarbon that occurs in crude oil in small amounts has an empirical formula of C3H4. The experimentally determined molecular mass of this substance is 121 grams/mole. What is the molecular formula of mesitylene? a = C9H12
  1. Caffeine, a stimulant found in coffee that contains 49.5 % carbon, 5.15 % hydrogen 28.9 % nitrogen and 16.5 % oxygen by mass, the molar mass is 195 grams/mole. Determine both the empirical and molecular formula of caffeine?

a = C4H5N2O = empirical formula, C8H10N4O2 = molecular formula.

5 Menthol, the substance we can smell in mentholated cough drops, is composed of C, H, and O. A .1005 gram sample is combusted (reacted with oxygen), producing .2829 grams of CO2 and .1159 grams of H2O. What is the empirical formula for menthol? If the compound has a molar mass of 156 grams/mole, what is its molecular formula? Show work on attached paper. Hint, find the mass of carbon present, then hydrogen. Oxygen mass can be then derived. ( do on attached lined paper)