To stand a chance means to have a possibility of something, usually winning. - The team stands a chance to win this season. 'Leave a chance' does not make sense. You could say, 'leave it to chance'. This would mean to not prepare or plan for something. - They planned for every possibility and left nothing to chance.

You'd need a wider context for 'to leave a chance', but how I believe you want to use it, it's wrong. "To stand a chance" is correct, and is often followed by 'of something'. "He stands a good chance OF WINNING. (notice that the verb is used in the ING (gerund) form). They didn't stand a chance OF SURVIVING the crash. 'of' is the preposition you need after 'stand a chance', and it's a good idea to make a note of the whole thing, rather than just 'stand a chance' on its own.

Depending on what you want to say: "to stand a chance" means the odds of winning or accomplishing an objective, for example: "Tom's football team didn't stand a chance against the opposing team." (The odds of winning are very low for Tom's team.) "leave to chance" means hoping for the best, but having no control over the outcome.