Question

If 5.65 grams of zinc metal react with 21.6 grams of silver nitrate, how many grams of silver metal can be formed and how many grams of the excess reactant will be left over when the reaction is complete? Show all of your work.
unbalanced equation: Zn + AgNO3 Zn(NO3)2 + Ag

Answer 1

The balanced chemical reaction is:

Zn + 2AgNO3 =  Zn(NO3)2 + 2Ag

To determine the amount of the reactant left, we have to determine which is the limiting and the excess reactant. We do as follows:

5.65 g Zn ( 1 mol / 65.38 g) = 0.09 mol Zn
21.6 g AgNO3 (1 mol / 169.87 g) = 0.13 mol AgNO3

The limiting reactant would be silver nitrate since it is consumed completely in the reaction. The excess reactant would be zinc. 

Excess Zinc = 0.09 mol Zn - (0.13 / 2) mol Zn = 0.025 mol Zn left

Answer 2

Answer:

1.3710 grams of silver metal can be formed.

0.4158 grams of the excess reactant will be left over when the reaction is complete

Explanation:

$Zn+2AgNO_3\rightarrow Zn(NO_3)_2+2Ag$

Moles of zinc metal =$\frac{5.65 g}{65.38 g/mol}=0.0864 mol$

Moles of silver nitrate = $\frac{21.6}{169.87 g/mol}=0.01271 mol$

According to reaction , 1 mole of zinc reacts with 2 mole of silver nitrate.

Then 0.0864 mol of zinc will react with:

$2\times 0.0864 mol=0.1728 mol$ silver nitrate

This means that zinc is in excessive amount.

So, the formation of silver metal will depend on moles of silver nitrate.

According to reaction 2 moles of silver nitrate produces 2 mole of silver metal.

Then 0.01271 moles of silver nitrate will produce:

$\frac{2}{2}\times 0.01271 mol=0.01271 mol$ of silver metal

Mass of 0.01271 mol of silver metal = 0.01271 mol × 107.87 g/mol = 1.3710 g

Moles of excessive reagent left

According to reaction , 1 mole of zinc reacts with 2 mole of silver nitrate.

Then 0.01271 mol of silver nitrate will react with:

$\frac{1}{2}\times 0.01271 mol=0.00635 mol$ of zinc

Moles of an excess reagent = 0.01271 mol - 0.00635 mol = 0.00636 mol

Mass of 0.00636 mol zinc:

0.00636 mol × 65.38 g/mol = 0.4158 g

1.3710 grams of silver metal can be formed.

0.4158 grams of the excess reactant will be left over when the reaction is complete