Exam 5: Thermochemistry: Energy Changes in Reactions

The integrated circuits in your cell phone and computer are made from the semiconductor silicon. The silicon is obtained from a really inexpensive starting material, sand, which is primarily SiO₂. One step in the purification of silicon is to separate it from solid impurities by forming the gas silicon tetrachloride. Given the following reactions, what is the overall enthalpy change in converting 1.00 mol of silicon dioxide into pure silicon? Reaction () (s)+2(s)\rightarrow (impure s +2(g) +690 ()+2(g)\rightarrow(g) -657 (g)+2(s)\rightarrow2(s)+(s) -625

When ammonium nitrate (NH₄NO₃)(s) is used in explosives, it decomposes to N₂(g), O₂(g), and H₂O(g). Write a balanced reaction equation for the decomposition of ammonium nitrate, and determine the standard enthalpy of reaction using standard enthalpies of formation: solid ammonium nitrate = -366 kJ/mol and water vapor = -242 kJ/mol.

The kinetic energy associated with the random motion of molecules is called ________

You have a summer job in a lead foundry. Your task is to identify how energy efficiency can be improved. You therefore need to know the minimum amount of energy it takes to raise 1 pound of lead (454 g) from room temperature (25°C) to its melting point (327°C) and then melt it. The specific heat capacity of lead is 0.159 J/(g .°C), the enthalpy of fusion is 24.7 J/g, and the molar mass is 207 g/mol.

Which statement regarding combustion of a sample of gasoline in a bomb calorimeter is correct?

Lightweight camping stoves typically use a mixture of C₅ and C₆ hydrocarbons, which is called white gas. Assuming white gas is 100% C₆H₁₄ with an enthalpy of combustion of -4,150 kJ/mol, how many grams of it must be used to heat 1.50 L of water from 20°C to 90°C? Assume all the energy is used to heat the water.

A 15 g piece of iron (C_P = 25.09 J/(mol · °C)) is heated to a temperature of 95°C and placed into a bucket containing 4.5 gal of water (C_P = 75.38 J/(mol · °C)) initially at 25°C. Eventually,

Which of the following fuels has the highest fuel value (kJ/g)?

How much work does a gas do when it expands against a constant pressure of 0.500 atm from a volume of 50.00 mL to a volume of 350.00 mL? (101.3 J = 1 L atm)

The inside of a perfectly insulated capped thermos bottle is an example of ________

Energy that an object has by virtue of its position is called ________

Isooctane is a good model compound for gasoline. When 1.14 g of isooctane (114 g/mol) reacts with excess oxygen in a constant pressure calorimeter, the temperature of the calorimeter increases by 10.0^oC. The heat capacity of the calorimeter is 5.46 kJ/^oC. Determine the molar enthalpy of combustion of isooctane.