How many moles of he are in 16 g of the element? ?

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

How does secondary succession differ from primary succession?

Which statement correctly describes other ways in which nebulae and stars are different? a. a star always has a higher density than a nebula. b. stars can form inside a nebula but a nebula can never be produced by any star. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star. reset submit