Answer
$11.5\%$
Work Step by Step
Number of moles of AgCl:
$0.1840\ g\div 143.33\ g/mol=1.284\ mmol$
From stoichiometry, number of moles of the compound: $0.642\ mmol$
Mass of the compound: $0.642\ mmol\times 221.03\ mg/mmol=141.9\ mg$
Mass percentage:
$0.142/1.236\times 100\%=11.5\%$
