Question

Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below:

2NO2 ---> 2NO2

Which of the following provides evidence that a chemical reaction occurs?

A) A gas is present.
B) The total number of atoms remains unchanged.
C) The state of matter remains the same.
D) The color of the gas changes from colorless to brown.

Answer 1

The evidence that a chemical reaction occurs in this equation is the change in color of the gas from colorless to brown.

Step-by-step explanation:

The evidence that a chemical reaction occurs in this equation is that the color of the gas changes from colorless to brown. This indicates a change in the chemical properties of the substance. Additionally, the equation shows that the total number of atoms remains unchanged, so option B is not the correct answer. The presence of a gas (option A) and the state of matter remaining the same (option C) do not necessarily indicate a chemical reaction.