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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Baksu888 on October 11, 2019, 08:58:33 PM

Title: Determining the number of moles/percent by mass of MgCl2 in mixture
Post by: Baksu888 on October 11, 2019, 08:58:33 PM

This is one of the questions on my AP Chemistry Quiz that my teacher asked me to revise on my own, but the problem is, I have no idea where to even begin with this problem. If you guys can give me a resource or help me out with some pointers that would be great!

Here's the problem:

In the second experiment, a student is given 2.94g of a mixture containing anhydrous MgCl₂ and KNO₃. To determine the percentage by mass of MgCl₂ in the mixture, the student uses excess AgNO₃(aq) to precipitate the chloride ion as AgCl(s). This means the MgCl₂ reacts with the AgNO₃ to create a solid AgCl. The student determines the mass of the formed AgCl precipitate to be 5.48g. On the basis of this information, calculate:

1.) The number of moles of MgCl₂ in the original mixture.
2.) The percent by mass of MgCl₂ in the original mixture.

Title: Re: Determining the number of moles/percent by mass of MgCl2 in mixture
Post by: Borek on October 12, 2019, 04:02:18 AM

Start with the reaction equation and follow the stoichiometry.

Title: Re: Determining the number of moles/percent by mass of MgCl2 in mixture
Post by: Baksu888 on October 12, 2019, 05:23:08 PM

https://imgur.com/QUA6RRf

Can you check my work?

Title: Re: Determining the number of moles/percent by mass of MgCl2 in mixture
Post by: Borek on October 12, 2019, 06:03:50 PM

Wasn't that hard.