To calculate the percent of silver in the coin, we need to determine the amount of silver present in the coin and express it as a percentage of the total weight of the coin. Here's how we can do that:

1. Calculate the moles of AgCl precipitated:

Moles of AgCl = mass of AgCl / molar mass of AgCl

Moles of AgCl = 6.21 g / 143.32 g/mol

Moles of AgCl = 0.0433 mol

2. Since AgCl is formed from the reaction of silver (Ag) and chloride (Cl) ions, the moles of AgCl are equal to the moles of Ag present in the coin. Therefore, the moles of Ag in the coin are 0.0433 mol.

3. Calculate the mass of Ag in the coin:

Mass of Ag = moles of Ag * molar mass of Ag

Mass of Ag = 0.0433 mol * 107.87 g/mol

Mass of Ag = 4.66 g

4. Calculate the percent of silver in the coin:

Percent of silver = (mass of Ag / total mass of coin) * 100

Percent of silver = (4.66 g / 6.80 g) * 100

Percent of silver ≈ 68.53%

Therefore, the coin contains approximately 68.53% silver.