Remark
The balance numbers in front of Ag and AgNO3 are both 2. That number is in moles.
Rule: if the moles are the same in the equation, then whatever you are given for one, will be the same for the other. So you have 0.854 moles of Ag. You will also have 0.854 moles of AgNO3
Answer: 0.854 <<<<<
The answer would be ethane (C2H4)
The answer is Br₂ since catalysts are regenerated at the end of a reaction.