1. The problem statement, all variables and given/known data Vapor density of a metal chloride is 66. Its oxide contains 53% metal. The atomic weight of the metal is ? 2. Relevant equations vapor density = 0.5 * molar mass 3. The attempt at a solution Using the above formula, I found the molar mass of the metal chloride as 132. I am stuck here, as the problem talks about the oxide containing 53% metal. In 100 g of Metal oxide, 47% is oxygen, i.e. roughly the weight of three oxygen atoms which is 48. The Formula is therefore M2O3 ? Does this mean that this metal is hexa valent? This doesn't seem right, because the mol wt of chlorine is 35.5 and six chlorine atoms would weigh 213 g whereas the sample is only 132 g. The choices for answer are 21, 54, 27.06 and 2.7. Logically I think the answer should be 54, as this would correspond to cobalt while the rest are not metals. Can anybody please explain how the answer is to be arrived at?