Answer;
-Change in pressure.
Explanation;
-Increasing the pressure on a reaction involving reacting gases increases the rate of reaction. If you increase the pressure of a gas, you squeeze it into a smaller volume.
-When you increase the pressure, the molecules have less space in which they can move. That greater density of molecules increases the number of collisions. When you decrease the pressure, molecules don't hit each other as often and the rate of reaction decreases. Pressure is also related to concentration and volume.
