Question

90 g of a silver coin was dissolved in strong nitric acid and excess of sodium chloride solution added. The silver chloride precipitate was dried and weighed 71.75 g. Calculate the precentage of silver in the coil (Atomic mass of Ag = 108)

Ag+2HNO₃→AgNO₃+NO₂+H2O

AgNO₃+NaCl→AgCl+NaNO₃

Answer 1

The percentage of silver in the coin is 60%.

Step-by-step explanation:

To calculate the percentage of silver in the coin, we first need to find the number of moles of silver in the silver chloride precipitate. The molar mass of silver chloride (AgCl) is the sum of the atomic masses of silver (108 g/mol) and chlorine (35.5 g/mol), which is 143.5 g/mol.

Given that the mass of the silver chloride precipitate is 71.75 g, we can calculate the number of moles of silver chloride:

Number of moles = mass / molar mass = 71.75 g / 143.5 g/mol = 0.5 moles

Since 1 mole of AgCl contains 1 mole of silver, the number of moles of silver is also 0.5 moles.

To find the percentage of silver in the coin, we need to calculate the mass of silver in 90 g of the coin:

Mass of silver = number of moles × molar mass = 0.5 moles × 108 g/mol = 54 g

Percentage of silver in the coin = (mass of silver / mass of coin) × 100% = (54 g / 90 g) × 100% = 60%