Which of the following would not necessarily indicate a chemical reaction?
change in temperature
chemical precipitation of a solid
production of a gas
change in volume

The correct answer is D. Change in volume

Explanation:

In a chemical reaction, new substances are formed and as a result, the original substances or reactants change chemically. This is the opposite of a physical change that involves only a change in physical properties, but not chemical ones.

In the case of volume, this is a physical property and refers to the space a substance occupies. Due to this, a change in volume is related to a physical change, but not a chemical one. For example, if you compress a gas, this reduces its volume, but the gas will not change its identity or properties. This implies a change in volume does not necessarily indicate a chemical reaction, but it indicates a physical change.

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.