What are emission spectra? a. the photons emitted when an electron drops down an energy level. b. the change in thermal patterns when energy is released. c. the change in incandescence that occurs when thermal emission moves into the visible spectrum. d. the photons absorbed when an electron goes up an energy level.

a spectrum of the electromagnetic radiation emitted by a source.

D

Explanation:

A. The photons emitted when an electron drops down an energy level.

When a source emits electromagnetic radiation then the spectrum is called as emission spectrum. It is emitted during the process when an atom makes its transition of energy levels to ground state.

Ground state is the state where atom possesses the lowest energy. When an atom or molecule comes down from higher energy level to lower energy level, it emits the spectrum which is called as emission spectrum.

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"