13. Predict whether at 27°C, the following reaction is spontaneous or not 4NH3 + 502
4NO + 6H,00​

Which position represents spring in the southern hemisphere? a) b) c) d)

The mass of a neutron is equal to the mass of a proton plus the mass of an electron. true or false false true

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.