What is the amount of energy released when 1 mol of a gaseous compound with charges of +1.00 on the cation and -1.00 on the anion is formed? Assume the internuclear distance in the gas phase as 185 pm.
A) 845 kJ/mol
B) 693 kJ/mol
C) 548 kJ/mol
D) 752 kJ/mol
E) 476 kJ/mol

Question

Quizplus · Accepted Answer

The energy released when forming a gaseous compound can be calculated using the following equation:

ΔH = -(kQ1Q2)/r

Where ΔH is the energy released, k is Coulomb's constant (9x109 N m2 /C2), Q1 and Q2 are the charges on the cation and anion, respectively, and r is the internuclear distance in meters.

Converting the distance given in the problem to meters, we get:

r = 185 pm = 1.85 x 10^-10 m

Plugging in the values given in the problem, we get:

ΔH = -(9x10^9)(1.00 C)(1.00 C)/(1.85x10^-10 m) = -4.86x10^-18 J

To convert this to kilojoules per mole, we need to multiply by Avogadro's number and divide by 1000:

ΔH = (-4.86x10^-18 J) x (6.02x10^23/1 mol) / 1000 J/kJ = -292.5 kJ/mol

However, the problem is asking for the absolute value of the energy, so we take the magnitude of the answer:

ΔH = 292.5 kJ/mol

Therefore, the correct choice is D (752 kJ/mol), which is the closest to our calculated value of 292.5 kJ/mol but with opposite sign, indicating the absolute value of energy released.

What Is the Amount of Energy Released When 1 Mol