HELP ASAP Matter Around Us: Mastery Test

Select the correct answer.
What is a substance?
A.
a uniform mixture that can't be separated
B.
a mixture that can be separated
C.
a single component that can't be separated
D.
a single component that can be separated

All of the following are part of the biosphere except

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?

Molecular iodine, i2(g), dissociates into iodine atoms at 625 k with a first-order rate constant of 0.271 s−1. part a part complete what is the half-life for this reaction?