Chemistry

Thermochemistry and Equilibrium

110 Questions

Thermochemistry and equilibrium problems focus on calculating bond energies, lattice enthalpy, and the Born Haber cycle. These concepts are vital for scoring well in chemistry sections. Regular practice ensures a clear understanding of energy changes in reactions.

Bond energy calculationsBorn Haber cycleLattice enthalpyEnthalpy of solutionThermochemical equations

Thermochemistry and Equilibrium Questions

Multiple choice chemistry energetics and thermochemistry bond energies and enthalpy changes bond enthalpies enthalpies for different types of reactions

The dissociation energy of $CH _4$ and $C _2H _6$ are respectively 360 and 620 kcal /mole. the bond energy $C-C$ is:

  1. 260 kcal /mole

  2. 180 kcal /mole

  3. 130 kcal / mole

  4. 80 kcal / mole
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Dissociation of energy of $CH _4$ base
=$\cfrac {\text{dissociation energy of }{CH _4}}{4}=\cfrac {360}{4}=90Kcal/mole$

Dissociation energy of $C _2H _6$

620=1(B.E of C-C bond+ 6 B.E of C-H bond)

620=B.E of C-C bond +6 $\times $90

B.E of C-C bond=620-540=80 kcal / mole
Multiple choice

What is the formula for chemical potential energy?

  1. $U = mgh$
  2. $U = rac{1}{2}mv^2$
  3. $U = rac{1}{2}kx^2$
  4. $U = - rac{k}{r}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chemical potential energy is the energy an object possesses due to its chemical composition. The formula for chemical potential energy is $U = -rac{k}{r}$, where $k$ is a constant and $r$ is the distance between the particles.

Multiple choice

What is the potential energy of a chemical reaction?

  1. $U = mgh$
  2. $U = rac{1}{2}mv^2$
  3. $U = rac{1}{2}kx^2$
  4. $U = - rac{k}{r}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The potential energy of a chemical reaction is $U = -rac{k}{r}$, where $k$ is a constant and $r$ is the distance between the particles.

Multiple choice

What is the typical accuracy of Configuration Interaction Theory calculations?

  1. Chemical accuracy (1 kcal/mol).

  2. Semi-quantitative accuracy (10 kcal/mol).

  3. Qualitative accuracy (100 kcal/mol).

  4. It depends on the size of the molecule and the level of theory used.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The accuracy of Configuration Interaction Theory calculations depends on the size of the molecule and the level of theory used. For small molecules, Configuration Interaction Theory can achieve chemical accuracy, while for larger molecules, it may only achieve semi-quantitative or qualitative accuracy.