What best describes the collisions between ideal gas molecules?

The molecules are continually colliding with each other and with the walls of the container. When a molecule collides with the wall, they exert small force on the wall The pressure exerted by the gas is due to the sum of all these collision forces. The more particles that hit the walls, the higher the pressure.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

elements make up everything, and they combine to make compounds.

the answer is c