Posted by **S-rth** on Tuesday, September 27, 2011 at 8:32pm.

An unknown element reacts with bromine to give bromide, MBr3. If 2.809g of the unknown element gives 27.765grams of MBr3, what is the element? ( give the symbol )

I dont understand the M in the MBr3...can someoen please help me with this question ASAP

thanks a lot

- i know this question was posted earlier but i did not understand something and bob did not reply to my question ( no prob , i understand you guys are busy but i really need help with this question, its worth a lot and im freaking out for the test tomm )

- Chemistry -
**Corey**, Wednesday, September 28, 2011 at 12:03am
The M stands for the unknown element; it binds to the Bromine. Bromine has a -1 charge, and there are three, it is highly likely that the element is Aluminum or Boron.

27.765 g MBr3-2.809 g M=24.956 g 3Br-

24.956 g Br* (1 mol Br/239.7 g)=

.104 mol Br

This is the same number as that of M, so there are .104 mol M.

2.809 g M/.104 mol M=26.98 g/mol M.

This is the molar mass of aluminum.

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