Question

20. What is the molecular formula for alkane, alkenes and alkynes?

15.What happens to a reaction at equilibrium when more reactant is added to the system?

Answer 1

For questions like this you should tell us what you think or at least something about what you don't understand about the question.
Alkanes are CnH(2n+2)
alkenes are CnH2n
alkynes are CnHn

In a reaction, for example,
A + B --> C + D
If more A is added or if more B is added the equilibrium shifts to the right.