Atomic mass? I'm not shre
I hope this helps in some way. I forgot to mention that the question states they want to find THE NUMBER OF MOLES for H2O. Yherefore, you would want mol of H2O on top.
Answer:- 
Explanations:- It's a double replacement reaction where a precipitate of silver(I)bromide is formed. A dpuble replacement reaction in general looks as AB + CD \rightarrow AD + CB
To balance the equation we need to multiply gold compounds on both sides by 2 and the balanced equation is..

1 2 3 4 5 and how the question ask
Answer: The suffixes of the names of polyatomic ions have a pattern associated with them. ... For example, the sulfite ion has three oxygen atoms whereas the sulfate ion has four oxygen atoms.