Question

Which statement(s) is/are true about bond enthalpy? (a) The bond energy for a triple bond between \(\mathrm{A}\) and \(\mathrm{B}\) is three times that of a single bond between \(\mathrm{A}\) and \(\mathrm{B}\). (b) \(\Delta H\) for the breaking of a bond is always a negative number. (c) Energy is required to make a bond. (d) Bond enthalpy is defined only for bonds broken or formed in the gaseous state. (e) The presence of \(\pi\) bonds does not influence the geometry of a molecule. However, the presence of \(\pi\) bonds affects the value of the bond enthalpy between two atoms.

Short answer

Question: Based on the analysis of the given statements about bond enthalpy, identify if each statement is true or false. a) The bond energy for a triple bond between A and B is three times that of a single bond between A and B. b) The ΔH for the breaking of a bond is always a negative number. c) Energy is required to make a bond. d) Bond enthalpy is defined only for bonds broken or formed in the gaseous state. e) The presence of π bonds does not influence the geometry of a molecule, but affects the value of the bond enthalpy between two atoms. Answer: a) False b) False c) False d) True e) Partially True

Step-by-step solution

Statement a

Statement a says that the bond energy for a triple bond between A and B is three times that of a single bond between A and B. This is not completely true. Although the bond energy for a triple bond is stronger than a single bond, it's not necessary that it will always be exactly three times the energy of a single bond. Hence, statement a is False.

Statement b

Statement b says that \(\Delta H\) for the breaking of a bond is always a negative number. This is incorrect. Breaking a bond always requires energy, so the change in enthalpy for bond breaking should be a positive number. Thus, statement b is False.

Statement c

Statement c claims that energy is required to make a bond. This is false. Energy is given out and not required when a bond is formed. Therefore, statement c is False.

Statement d

Statement d states that bond enthalpy is defined only for bonds broken or formed in the gaseous state. This is true. Bond enthalpy is a measure of the energy required to break one mole of bonds in a gaseous compound under specific conditions. Therefore, statement d is True.

Statement e

Statement e consists of two parts: 1) The presence of \(\pi\) bonds does not influence the geometry of a molecule. 2) The presence of \(\pi\) bonds affects the value of the bond enthalpy between two atoms. The first part is false, as \(\pi\) bonds do affect the molecule's geometry by limiting its rotation. The second part is true, as \(\pi\) bonds do have a higher bond enthalpy compared to sigma bonds. So, statement e is considered Partially True. In conclusion, only statement d is entirely true, while statement e is partially true. All other statements are false.