Lesson 3 unit 4 - 1Sec

Shown in the reaction profile are the changes in chemical energy during a reaction.

Energy cannot be created nor destroyed, only changed from one form to another. Which of the following processes is least likely to occur due to the change in chemical energy shown in the figure?

• The container for the reaction mixture vibrates less rapidly.

• Air molecules above the reaction mixture increase in temperature.

• Light is emitted by reacting molecules.

• Reactant and product molecules gain kinetic energy.

• Solvent evaporates from the reaction mixture.

Labelled in the diagram are the chemical energies of three compounds, a to c.

Which of the labelled compounds is most stable?

• c

• a

• b

Labelled in the diagram are the chemical energies of three compounds, a to c.

Which of the labelled compounds is least stable?

• c

• a

• b

Illustrated in the reaction profiles are the changes in chemical energy during a range of processes.

Which of the diagrams best describes the changes in chemical energy for a stick of dynamite during an explosion?

• a

• b

• c

Illustrated in the reaction profiles are the changes in chemical energy during a range of processes.

Which of the diagrams best describes the changes in chemical energy for a packet of pasta stored in a kitchen cupboard?

• a

• b

• c

Illustrated in the reaction profiles are the changes in chemical energy during a range of processes.

Which of the diagrams best describes the changes in chemical energy for a piece of aluminum being heated by a blowtorch?

• a

• b

• c

The reaction profile for a chemical reaction is shown in the diagram below. Which label corresponds to the change in enthalpy, Δ𝐻,of the reaction?

• A

• B

• C

• ALL THE ABOVE

Ethanethiol, a volatile liquid with a strong smell, is added to liquefied petroleum ga2s to aid the detection of gas leaks. The compound is produced by reacting ethene with hydrogen sulfide (H2S) , according to the shown equation.

The total energy change for this reaction is -69 KJ/mol

The energies of selected bonds are given in the table.

Calculate, to the nearest kilojoule per mole (kJ/mol), the average energy of the S-H bonds in H2S and ethanethiol.

…………… KJ/mol

• 358

• 360

• 365

• 313

Shown in the figure are two reactions involving sulfur dioxide (SO2) and sulfur trioxide (SO3) The total energy changes for the reactions, ΔH are given per mole of SO2 reacted

The energies of selected bonds are given in the table.

Calculate, to the nearest kilojoule per mole, the energy of the S=O bond in SO3

………………… KJ/mol

• 470

• 480

• 450

• 567

Shown in the figure are two reactions involving sulfur dioxide (SO2) and sulfur trioxide (SO3) The total energy changes for the reactions, ΔH are given per mole of SO2 reacted

The energies of selected bonds are given in the table.

Calculate, to the nearest kilojoule per mole, the energy of the O-F bond in OF2

……………………… KJ/mol

• 195

• 230

• 234

• 345