Question

Why do real gases deviate from ideal gas behaviour?

Answer 1

See below

Explanation:

Real gases are not perfect identical spheres, meaning they come in all different shapes and sizes for example the diatomic molecules, unlike the assumption of them being perfect identical spheres which is an assumption made for ideal gases.

Real gas collisions are not perfectly elastic, meaning Kinetic Energy is lost upon impact, unlike the assumption made for ideal gases which states that ideal collisions are perfectly elastic.

And finally real gases have intermolecular forces like London Dispersion acting on them, unlike the assumption for the ideal gases which states that they have no intermolecular forces.

Answer 2

See below.

Explanation:

An ideal gas is a gas that follows the assumptions of the Kinetic Molecular Theory of Gases (KMT).

Here are the assumptions of the KMT, in case you didn't know them:

https://www.acschools.org/cms/lib/PA01916405/Centricity/Domain/362/KMT%20Power%20Point.pdf

Real gases deviate from ideal behavior because 1) they have intermolecular forces between molecules, 2) collisions aren't always elastic (also due to intermolecular forces), and 3) gas molecules have volume.

I hope that helps!