What is the oxidation number of chromium in cr2o7 4-? a. +3 b. +4 c. +5 d. +6

C. +5

Explanation:

Oxygen is always -2. And the sum of the oxidation numbers must be equal to the charge. So:

2x + 7(-2) = -4

2x - 14 = -4

2x = 10

x=5

african americans demonstrated their newly found freedom by relocating often in search of relatives whom they had been separated from during slavery. others established schools to educate freed people and they built institutions such as churches and political organizations to advocate for their rights.

gas

explanation:

smoke is the matter of a gas