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A sample of a mineral was found to be 12% carbon by mass, with the remaining mass being a combination of calcium and oxygen. Given the sample has the same number of mols of carbon and calcium. What is the mass \% of oxygen in the unknown sample?
How many mls of dichloromethane (CH2​Cl2​)(d=1.33 g/ml) would have the same number of mols of chlorine as 1.5 mL of chloroform (d=1.49 g/ml) ?