Anonymous“
1.Everyone will have an opportunity/chance to comment.
2.He was never given the opportunity/chance of going to college.
3.You'll have the opportunity/chance to ask any questions at the end.
4.There was no opportunity/chance for further discussion.
5.At least give him the opportunity/chance of explaining what happened.
6.We won’t get another chance/opportunity for a holiday this year.
7.There will be an chance/opportunity for parents to look around the school.
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Anon:
Opportunity implies something offered or possibly available based on effort or skill.
Chance is most often associated with pure luck. So there is only one of your examples (#6), where I could use "chance" instead of "opportunity."
The choice would depend on the context. For example:
My boss is demanding us to work more hours this year, which means that we won't have the opportunity to take more than one holiday.
I enetered a contest for a free all-paid holiday. This means that I might have the chance for two holidays this year!