Yes. In a homogeneous mixture the hydrogen and oxygen are not chemically combined; in water vapor, they are. You can separate a homogeneous mixture of hydrogen and oxygen by physical means, such as by cooling the mixture until the oxygen liquefies. If you cool water vapor you're just going to get liquid water and then ice - not two separate substances. That's because compounds can only be separated into their elements by chemical means.
Calcium metal with chromium(III) chloride would react. Calcium metal is more reactive than chromium metal; therefore, putting calcium metal in chromium chloride would create a reaction, where as putting chromium metal in calcium chloride would not form any reaction.
