Question

11. Silver metal may be precipitated from a solution of silver nitrate by placing a copper strip into the solution. What mass of NaNO3 would you dissolve in water in order to get 1.00 g of silver?

Answer 1

Answer: The mass of silver nitrate that must be dissolved is 1.58 grams.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$   ......(1)

Given mass of silver = 1 g

Molar mass of silver = 107.86 g/mol

Putting values in equation 1, we get:

$\text{Moles of silver}=\frac{1g}{107.86g/mol}=0.0093mol$

The chemical equation for the reaction of silver nitrate and copper follows:

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

By Stoichiometry of the reaction:

2 moles of silver is produced from 2 moles of silver nitrate

So, 0.0093 moles of silver will be produced from = $\frac{2}{2}\times 0.0093=0.0093moles$ of silver nitrate

Now, calculating the mass of silver nitrate from equation 1, we get:

Molar mass of silver nitrate = 169.87 g/mol

Moles of silver nitrate = 0.0093 moles

Putting values in equation 1, we get:

$0.0093mol=\frac{\text{Mass of silver nitrate}}{169.87g/mol}\\\\\text{Mass of silver nitrate}=1.58g$

Hence, the mass of silver nitrate that must be dissolved is 1.58 grams.