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.
2NO+ 02
+ 2NO
Colorless
Colorless
gas
Brown
gas
gas
Which of these provides evidence that a chemical reaction occurs?
O A. A gas is present
OB. The total number of atoms remains unchanged.
a C. The state of matter remains the same.
D. A brown gas is produced.