thermochemistry

thermochemistry

Multiple Choice

The SI unit of heat and energy is the __________.

• calorie
• heat
• joule
• watt

Multiple Choice

What mass of P₄ must be reacted to produce 5905 kJ of energy?
P₄ + 6Cl₂ --> 4PCl₃ + 2439 kJ

• 25.43 g
• 563.0 g
• 2.421 g
• 300.0 g

Multiple Choice

In an endothermic reaction the system is releasing energy.

• True
• False

Multiple Choice

In an exothermic process the surrounding looses heat. 

• True
• False

Multiple Choice

The thermochemical equation for the combustion of methanol is shown below.

CH3OH() + 3/2 O2(g) → CO2(g) + 2 H 2O(g)ΔrH° = –638.7 kJ/mol-rxn

What is the enthalpy change for the combustion of 8.59 g CH3OH?

• a. –171 kJ

• –19.9 kJ

• c. –2.38 × 10³ kJ

• d. –5.49 × 10³ kJ

• e. –1.76 × 10 ⁶ kJ

Multiple Choice

Iron oxide reacts with aluminum in an exothermic reaction.

Fe2O3(s) + 2 Al(s) → 2 Fe(s) + Al2O3(s)

The reaction of 5.00 g Fe2O3 with excess Al(s) evolves 26.6 kJ of energy in the form of heat. Calculate the enthalpy change per mole of Fe2O3 reacted.

• –5.32 kJ/mol

• b. –1.33 × 10² kJ/mol

• –2.12 × 10² kJ/mol

• –8.50 × 10² kJ/mol

Multiple Choice

When methane, CH4, and oxygen, O2, are mixed in a stove and ignited, a lovely blue flame results. The balanced equation is: CH₄(g) + 2O₂(g) 2H₂O(g) + CO₂(g) What can be said about the energy involved in this chemical reaction?

I. The average kinetic energy of the products is greater than that of the reactants.

II. The chemical energy stored in the reactants is greater than the chemical energy stored in the products.

III. Chemical energy in the reactants is changed into heat energy and light energy.

• I only

• II only

• III only

• I, II, and III

Multiple Choice

The diagram represents two solids and the temperature of each. What occurs when the two solids are placed in contact with each other?

• Heat energy flows from solid A to solid B. Solid A decreases in temperature

• Heat energy flows from solid A to solid B. Solid A increases in temperature

• Heat energy flows from solid B to solid A. Solid B decreases in temperature.

• Heat energy flows from solid B to solid A. Solid B increases in temperature.

Multiple Choice

During an exothermic reaction, heat content in the surroundings increases because

• heat energy is destroyed during reactions

• the reaction absorbs heat energy

• the energy contained in the reactants is lower then the products

• the energy contained in the products is lower than the reactants

Multiple Choice

The potential energy diagram of a reaction is shown. Which statement below is correct relating to this reaction?

• #1 represents the enthalpy change for this exothermic reaction.

• #2 represents the enthalpy change for this endothermic reaction.

• #3 represents the enthalpy change for this endothermic reaction.

• #4 represents the enthalpy change for this exothermic reaction.

Multiple Choice

What type of reaction is shown in the reaction pathway?

• endothermic reaction
• exothermic reaction

Multiple Choice

The SI unit of heat and energy is the __________.

• calorie
• heat
• joule
• watt