[DelquesOtaku]

Hello I did a lab on Combustion of ethyne and the question was
  was it complete or incomplete and show the equation... 
We saw that it was incomplete becuase there was burnt carbon and the test tube turned charcol black. I need help with the equation because most websites say its complete and shows the equation as complete.

Shouldn't the equation be like this:

C2H2 + O2 ---->   co + co2 + H2O

[Arkcon]

Carbon monoxide and carbon dioxide are both colorless gasses.  If you want to include your black solid observed in the reaction, you'll have to include it in your products, then try to balance.

[Borek]

Note: whether combustion is complete or not doesn't depend on what they write on the web, but on the relative amounts of ethyne and oxygen.