Understanding Bond Enthalpy and Reaction Enthalpy

The video tutorial explains bond enthalpy, the energy required to break one mole of a bond in the gas phase, and how it can be used to calculate the enthalpy of a reaction. It covers the properties of bond enthalpy, such as its positivity when breaking bonds and negativity when forming bonds. The tutorial provides an example of calculating reaction enthalpy using bond enthalpies for the hydrogenation of propine to propane, demonstrating the process of identifying bonds broken and formed, and using their enthalpy values to determine the overall reaction enthalpy.

What is bond enthalpy?

• The energy change during a chemical reaction.

• The energy released when a bond is formed.

• The energy required to break one mole of a bond in the gas phase.

• The energy required to form one mole of a bond.

Why is bond enthalpy always positive?

• Because bonds are always formed in the gas phase.

• Because energy is released when a bond is broken.

• Because energy is required to break a bond.

• Because it is measured in kilojoules per mole.

What happens to energy when a bond is formed?

• Energy is absorbed.

• Energy is released.

• Energy remains constant.

• Energy is converted to mass.

Which of the following is a method to estimate the enthalpy of reaction?

• Using Avogadro's number.

• Using bond enthalpies.

• Using the ideal gas law.

• Using the periodic table.

In the reaction between propine and hydrogen, what type of bond is broken?

• Carbon-oxygen double bond.

• Carbon-carbon single bond.

• Carbon-carbon triple bond.

• Hydrogen-oxygen bond.

How many hydrogen-hydrogen bonds are broken in the example reaction?

• Four

• Three

• One

• Two

What is the bond enthalpy of a carbon-carbon triple bond?

• 346 kJ/mol

• 436 kJ/mol

• 413 kJ/mol

• 835 kJ/mol

What is the bond enthalpy of a hydrogen-hydrogen bond?

• 835 kJ/mol

• 436 kJ/mol

• 413 kJ/mol

• 346 kJ/mol

What is the overall enthalpy change for the reaction between propine and hydrogen?

• Negative 291 kJ/mol

• Zero kJ/mol

• Positive 291 kJ/mol

• Positive 436 kJ/mol

What does a negative delta H indicate about a reaction?

• The reaction is exothermic.

• The reaction is at equilibrium.

• The reaction does not occur.

• The reaction is endothermic.