All categories

3 years ago

Consider an ionic compound, MX2, composed of generic metal M and generic, gaseous halogen X.

Chemistry

1 answer:

siniylev [52]3 years ago

5 0

Lattice energy U(MX2) to calculate

Use Born-Haber(-Fajans) Cycle

http://en.wikipedia.org/wiki/Born%E2%80%...

M(s) + X2 → MX2(s) ΔHf°MX2 = -957 kJ mol^-1

M(s) →ΔHsub(M)→ M(g) ΔHsub = 123kJ mol^-1

M(g) →ΔHIE1(M)→ M^+ + e⁻ 757 kJ mol^-1

M^+→ΔHIE2(M)→ M^2+ + e⁻ 1451 kJ mol^-1

X2 →ΔHBE(X2)→ 2X +153 kJ mol^-1

X + e⁻→ΔHEA(X)→ X^- -313 kJ mol^-1

ΔHfo = U + ΔHsub(M) + IE1 + IE2 + ΔHdissX2 + 2EA1(X)

-957= U + 123 + 757 + 1451 + 153 – 626 = U + 1858

U = -2815 kJ mol^-1 The –ve sign is often dropped

You might be interested in

In which of the following compounds does the carbonyl stretch in the IR spectrum occur at the lowest wavenumber?

klio [65]

Answer:

a. Cyclohexanone

Explanation:

The principle of IR technique is based on the vibration of the bonds by using the energy that is in this region of the electromagnetic spectrum. For each bond, there is a specific energy that generates a specific vibration. In this case, you want to study the vibration that is given in the carbonyl group C=O. Which is located around 1700 cm-1.

Now, we must remember that the lower the wavenumber we will have less energy. So, what we should look for in these molecules, is a carbonyl group in which less energy is needed to vibrate since we look for the molecule with a smaller wavenumber.

If we look at the structure of all the molecules we will find that in the last three we have heteroatoms (atoms different to carbon I hydrogen) on the right side of the carbonyl group. These atoms allow the production of resonance structures which makes the molecule more stable. If the molecule is more stable we will need more energy to make it vibrate and therefore greater wavenumbers.

The molecule that fulfills this condition is the cyclohexanone.

See figure 1

I hope it helps!

4 0

3 years ago

Which segement of the heating curve shown above represents an increase in the potential energy, but no change in the kinetic ene

Ede4ka [16]

Answer: Option (b) is the correct answer.

Explanation:

Kinetic energy is defined as the energy obtained by the molecules of an object due to their motion.

Also, it is known that kinetic energy is directly proportional to temperature.

Mathematically, K.E = $\frac{3}{2}kT$

where, T = temperature

Whereas potential energy is defined as the energy obtained by an object due to its position.

Mathematically, P.E = mgh

where, m = mass

g = acceleration due to gravity

h = height

Therefore, in the given curve when temperature remains constant then kinetic energy of molecules will also remain.

Hence, we can conclude that the segment QR represents an increase in the potential energy, but no change in the kinetic energy.

7 0

3 years ago

An ionic compound is composed of elements X and Y. X forms

mote1985 [20]

Answer: X2Y3

Explanation: I had the same question ;) (and got it right)

7 0

2 years ago

Do simple molecules conduct electricity? and why?

ira [324]

Yes they have electrons

7 0

3 years ago

Which of the following characteristics would make a gas non-ideal?

Marysya12 [62]

Answer:

A. The gas molecules possess kinetic energy.

Explanation:

The characteristics of the Ideal gases are given by the Kinetic Theory of gases which are as follows:-

Gases consist of particles in constant, random motion. They continue in a straight line until they collide with something—usually each other or the walls of their container.

Particles are point masses with no volume. The particles are so small compared to the space between them, that we do not consider their size in ideal gases.

No molecular forces are at work. This means that there is no attraction or repulsion between the particles.

Gas pressure is due to the molecules colliding with the walls

8 0

3 years ago