Test Review - Exam # 2

10 March, 1998, 7:00 PM

The examination will involve questions on the following topics:

• Stoichiometry including limiting reagents
• Balancing chemical reactions, specifically acid/base and combustion
• Solution concentrations including ppm and moles/liter
• Dilution of solutions to find new concentrations or given a desired concentration to find the final volume needed
• Stoichiometry problems involving solutions
• Basic definitions of thermochemistry including: heat, work, kinetic energy, potential energy, Enthalpy, standard states, heat of reaction, heat of formation, endothermic, exothermic
• Hess' Law problems solving both for a heat of reaction or for an unknown heat of formation
• Nomenclature (just in case you think I forgot)

Example problems.

Stoichiometry:

Given the reaction:

BaCO₃ + 2 HNO₃ -----> Ba(NO₃)₂ + CO₂ + H₂O

How many grams of barium nitrate will be made if we react 34.2 g of barium carbonate with 250 ml of a nitric acid solution that is 0.22 M?

If we are given 5.00 liters of a solution of industrial waste that is found to be 45.6 ppm in lead, what will be the final concentration if we pour this into an 8,500 liter holding tank?

A gallon of gasoline, C₈H₁₈, has a mass of approximately 3,200 g. How many grams of carbon dioxide would be formed when this gasoline is burned? Assume the final products to be CO₂ and H₂O.

The enthalpy of formation of gasoline is - 250 kJ/mole. (a) What is the heat of combustion of one mole of gasoline? (b) How much energy is released when the gallon of gasoline described in problem 3 is burned? Note, use the tables of heats of formation in your book to solve these problems.

The heat of combustion of cyclohexane, C₆H₁₂, is found to be -3920 kJ/mole. Use Hess' Law to find the heat of formation of cyclohexane.

How much heat is necessary to raise the temperature of 500 ml of water from 25 ^oC to 89 ^oC? If this same amount of heat were put into a 300 g piece of copper that has a specific heat of 0.37 J/^oC g, what would be its final temperature assuming that it starts at 25 ^oC?

The body carries out the metabolism of ethanol, C₂H₅OH, by first oxidizing it to acetaldehyde, C₂H₄O. The reaction is:

C₂H₅OH + ½ O₂ --------> C₂H₄O + H₂O

If the heat of formation of ethanol is -277.7 kJ/mol and that of acetaldehyde is -192.3 kJ/mol, what is the heat of reaction for the conversion of ethanol to acetaldehyde?