Step 1
The reaction must be written and balanced:
CuCl2 + 2NaNO3 = Cu(NO3)2 + 2NaCl
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Step 2
The limiting reagent
Information needed:
The molar masses of CuCl2 (134,4 g/mol) and NaNO3 (84,9 g/mol)
By stoichiometry:
1 mole CuCl2 = 134.4 g
1 mole NaNO3 = 84.9 g
134.4 g CuCl2 ---------- 2 x 84.9 g NaNO3
15 g CuCl2 ---------- X = 18.95 g NaNO3
For 15 g CuCl2, 18.95 g of NaNO3 is needed, but there is 20 g. Therefore, The limiting reagent is CuCl2 and the excess is NaNO3
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Step 3
Amount of the excess reagent leftover:
20 g NaNO3 - 18.95 g NaNO3 = 1.05 g leftover
Answer:
The limiting reagent = CuCl2
The amount of excess leftover = 1.05 g NaNO3