What is meant by the statement ' protential difference between point A and Point B in an electric circuit is 1 V' ?

The potential difference is considered as the change in terms of voltage or Del V. It is measured in terms of voltage so that statement got the name voltage change between point A & B is 1. It means that I joule of work is carried out for moving the 1 coulomb of charge from the point A to B.

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.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.