A chemist finds a sample in the lab that he knows is either sodium selenate (which has the same formula as sodium sulfate, except selenium replaces the sulfur) or sodium arsenite (which has the same formula as sodium phosphite, except arsenic replaces the phosphorus). He needs to know which compound it is so he may dispose of it properly. The chemist dissolves 2.00g of the substance in 10.00g of water and finds that the freezing point of the solution is 7.8C. Is the substance more likely to be sodium selenate or sodium arsenite, or is the chemist unable to tell which substance he has? Justify your answer and use calculations to support you