# Homework Help: [Chem] Determining Masses from Concentration

1. Sep 26, 2007

### dt_

1. The problem statement, all variables and given/known data
In lab, a student decides to analyze a 0.6118 g sample containing only magnesium chloride and sodium chloride. He does this by adding 145 milliliters of 0.1006 M silver nitrate. A precipitate, silver chloride, is formed, which has a mass of 1.7272 grams. Using this data, calculate the mass of each of the original sample's components.

2. Relevant equations

M = mol / L

$$MgCl_{2} + NaCl + AgNO_{3}$$ ...?

3. The attempt at a solution

I'm not really sure where to start here; my instinct is to multiply the volume of the silver nitrate by its molarity to get the number of moles. But I'm not sure what to do next, and I don't know what the products of the reaction are, other than the silver chloride precipitate. And besides, how would I able to find out how much mass there is of the individual components in the original sample if the problem only gives the total mass of these two components? Can anyone help me out? (Thanks in advance!!

2. Sep 27, 2007

### chemisttree

Start by writing out the precipitation reaction. This will give you the ratio of moles of silver chloride to moles of magnesium chloride plus sodium chloride.
Do you know how to determine the number of moles of silver chloride produced with the given data?
Hint: more data is given to you than you need to answer this question. Which data is unnecessary?

Last edited: Sep 27, 2007