Friction from a car's brakes causing it to stop is it a contact force?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

Generally, observed behavior that can be formulated into a statement, sometimes mathematical in nature, is called a(n): a. observation. b. measurement. c. theory. d. natural law. e. experiment.

What is the significance sodium hydroxide and hydrochloric acid