The pile of ash left after a fire burns out demonstrates what concept? a. original materials remain after a physical change. b. a chemical change forms new substances. c. physical properties are never stable. d. fire recycles most substances.

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

Base your answer on the information below and on your knowledge of chemistry. nitrogen dioxide, no2, is a dark brown gas that is used to make nitric acid and to bleach flour. nitrogen dioxide has a boiling point of 294 k at 101.3 kpa. in a rigid cylinder with a movable piston, nitrogen dioxide can be in equilibrium with colorless dinitrogen tetroxide, n2o4. this equilibrium is represented by the equation below. 2no2(g) n2o4(g) + 58kj at standard pressure, compare the strength of intermolecular forces in no2(g) to the strength of intermolecular forces in n2(g).

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.