Oxidation number of CrO4-2 {with solution }

What is a scientific theory? a. a scientist's guess about how something works b. the results of an experiment obtained using the scientific method c. a proven fact that will never change d. an idea that is backed by data from many sources

What is the temperature of one mole of helium gas at stp?

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