Solved: Calculate Ion Concentration (27.6 g)

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Discussion Overview

The discussion revolves around calculating ion concentration from a given mass of magnesium bromide (MgBr2). It includes a review of dissociation equations and the implications for concentration calculations.

Discussion Character

  • Homework-related

Main Points Raised

  • One participant presents a calculation for ion concentration based on a mass of 27.6 grams of MgBr2.
  • Another participant questions the correctness of the initial calculation and points out an error in the dissociation equation, suggesting that the concentration of bromide ions is twice that of MgBr2.
  • A clarification is provided regarding the notation of bromide ions, explaining that Br- ions dissociate from MgBr2 in solution, while Br2 refers to bromine as a diatomic element.
  • A participant expresses gratitude for the assistance received in the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the initial calculation, as there are differing views on the dissociation and concentration implications.

Contextual Notes

There are unresolved aspects regarding the initial calculation of moles and the interpretation of the dissociation equation, which may depend on the definitions used for concentration and dissociation.

temaire
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[SOLVED] Ion concentration

Homework Statement


http://img225.imageshack.us/img225/9918/chemch0.jpg​


Homework Equations


C = n/v


The Attempt at a Solution


My work is shown up above. Sorry if my work looks a little messy. My answer is 27.6 grams.
 
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I just want someone to tell me if I'am right, and correct me if I'am not.
 
good effort

your error is in your dissociation equation

MgBr2 --> Mg+2(aq) + 2Br-(aq)

the bromide ion is twice the concentration of the MgBr2 so the moles of MgBr2 is half what you calculated (.15/2).

your mass of MgBr2 is half of your answer
 
But isn't Br supposed to have a subscript of 2?
 
MgBr2 is a compound that dissociates into its ions in water.

the Br- ions don't stay together in water so you get 2 Br- ions

Br2 by itself is only written when you are referring to bromine as an diatomic element, not as ions in solution
 
Thanks a lot for the help. :approve:
 

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