What is a catalyst defined as? a. a substance that speeds up a reaction only b. a substance that speeds up a reaction, and is not used up c. a substance that speeds up a reaction, and is completely used up d. a substance that slows down a reaction, and is completely used up

Acompound has a molar mass of 92.02 grams/mole, and its percent composition is 30.4% nitrogen (n) and 69.6% oxygen (o). what is its molecular formula? a. n2o4 b. no2 c. n2o d. n4o2

Observation and experimentation have led many scientists to accept a theory about the origin of the universe. this theory is called the big bang theory. scientific evidence collected and observed by scientists around the world suggests that the universe is ever expanding from a hot and dense initial state. what makes this a scientific theory? (2 points)

Which description best characterization the motion of particles in a solid