Which statements describe the death of stars? Check all that apply.
A. Astar's final stages of life depend on its mass.
Stars die when they run out of fuel.
B. When a star starts to die, its core expands.
C. The outer portion of the star contracts.
D. All stars become black holes when they die.

Nitric acid can be formed in two steps from the atmospheric gases nitrogen and oxygen, plus hydrogen prepared by reforming natural gas. in the first step, nitrogen and hydrogen react to form ammonia: (g) (g) (g) in the second step, ammonia and oxygen react to form nitric acid and water: (g) (g) (g) (g) calculate the net change in enthalpy for the formation of one mole of nitric acid from nitrogen, hydrogen and oxygen from these reactions. round your answer to the nearest .

A5 mole sample of liquid acetone is converted to a gas at 75.0°c. if 628 j are required to raise the temperature of the liquid to the boiling point, 15.600 kj are required to evaporate the liquid, and 712 j are required to raise the final temperature to 75.0°c, what is the total energy required for the conversion?

Which of the following is a property of nonmetals? a.nonmetals are ductile. b.nonmetals have a shiny luster. c.nonmetals have high density. d.nonmetals are nonconductors.