Answer:
1.75 moles of copper must react to form 3.50 mol of Ag.
Explanation:
[tex]Cu + 2AgNO_3\rightarrow 2Ag + Cu(NO_3)_2[/tex]
According to reaction 2 moles of silver are obtained from 1 mole of copper.
Then 3.50 mole of Silver will be obtained from:
[tex]\frac{1}{2}\times 3.5 mol=1.75 mol[/tex]
1.75 moles of copper must react to form 3.50 mol of Ag.