Final answer:
To determine the mass of pure AgNO3 and the percentage of AgNO3 in the sample, calculate the moles of AgCl formed and then convert to moles of AgNO3. The acid added is in excess if the moles of HCl used are less than the moles of AgNO3, and it is just the exact amount needed if the moles are equal.
Step-by-step explanation:
To determine the mass of pure AgNO3 present in the impure sample, we need to calculate the amount of AgCl formed. From the given information, we know that 0.213g of AgCl is recovered. Since 1 mole of AgNO3 reacts with 1 mole of AgCl, we can use the molar mass of AgCl (143.32 g/mol) to find the moles of AgCl formed. Once we have the moles of AgCl, we can convert it to moles of AgNO3 using the stoichiometry of the reaction. Finally, we can calculate the mass of pure AgNO3 by multiplying the moles of AgNO3 with its molar mass. The percentage of AgNO3 in the sample can be calculated by dividing the mass of pure AgNO3 by the mass of the impure sample and multiplying by 100.
To determine if the acid added is in excess or just the exact amount needed to react completely with AgNO3, we need to calculate the moles of AgNO3 from the mass of AgCl recovered. The moles of AgNO3 should be equal to the moles of HCl used. If the moles of HCl used are less than the moles of AgNO3, it means that the acid added is in excess. If the moles of HCl used are equal to the moles of AgNO3, it means that the acid added is just the exact amount needed to react completely.