C. How many grams of Cu react with 5.65 grams of AgNO3?

we need 1.06g of Cu to react with 5.65g of AgNO₃

Explanation:

C u +2 AgNO₃ = Cu(NO₃ )₂ + 2 Ag

the mole ratio between Copper and silver nitrate is 1:2  meaning we need  2 moles of silver nitrate for every mole of copper that takes part in the reaction.

the molar mass of Cu  is 63.55

the molar mass of AgNO₃ is 107.8682+ 14 + (16x3) = 107.8682+ 14 + 48=  169.87682≈169.88g

for every 63.55 g of Cu reaction with  2(169.88g of AgNO₃)= 339.736g of AgNO₃

if x grams of Cu react with 5.65 grams of AgNO₃

63.55g= 339.736g

x = 5.65g

cross multiply

339.736x = 5.65 x 63.55 = 359.0575

x = 359.0575/339.736 = 1.05687210069≈1.06

we need 1.06g of Cu to react with 5.65g of AgNO₃

it means there are 3 atoms of oxygen