What is enthalpy? O the heat given off during an exothermic reaction
O the heat absorbed or released during a phase change
o the heat content of a system at constant pressure
o the heat absorbed during an endothermic reaction

the heat content of a system at constant pressure.

Explanation:

Enthalpy is defined as the heat content of a system at constant pressure.

It is the heat absorbed or released during a reaction at constant pressure,denoted as ΔH.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.