There are many impossible events. Here are a few.
I'm sure you can think of at least 15 more:
-- Pull 5 multiples of 3 from the bag.
-- Pull 3 multiples of 5 from the bag.
-- Pull 7 odd numbers from the bag.
-- Pull 7 even numbers from the bag.
-- Pull two slips from the bag whose sum is more than 21 .
-- Pull three slips from the bag whose sum is more than 33 .
-- Pull two slips from the bag whose sum is less than 3 .
-- Pull three slips from the bag whose sum is less than 6 .
-- Pull two slips from the bag whose product is more than 132 .
-- Pull two slips from the bag whose product is less than 2 .
etc.