Hello, 

Here you are some interesting information I found on the net explaining the difference between mix and mixture. I hope it is of help.

                          MIX OR MIXTURE ? 

 «Mix’ and ‘mixture’ are roughly interchangeable. ‘Mix’ sometimes implies that it was mixed together sometime in the past (e.g., cake mix — pre-made ingredients to make a cake), while ‘mixture’ definitively keeps things in the present (e.g., ‘Now that you have combined the eggs and flour, add sugar to the mixture.’)

‘Mixture’ is more common for this reason, but if you’re talking about something like cake mix, which is already made, then you usually will use ‘mix’.