Identity of metal from electrolysis

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Discussion Overview

The discussion revolves around identifying a trivalent metal ion based on the results of an electrolysis experiment. Participants analyze the data provided, including current, time, and mass of the metal plated out, to determine which metal from a given list corresponds to the calculated molar mass.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • One participant calculates the total charge using the formula current*time, resulting in 3000 coulombs, and subsequently determines the moles of electrons involved in the electrolysis.
  • It is noted that for a trivalent metal ion, the moles of metal can be calculated as one-third of the moles of electrons, leading to a value of 0.010364 moles of metal.
  • Another participant suggests using a formula to calculate molar mass directly from the mass of the metal and the number of moles, arriving at a molar mass of 113.86 g/mol.
  • Comparisons are made between the calculated molar mass and the molar masses of the metals listed, with indium being highlighted as the closest match based on the differences calculated.

Areas of Agreement / Disagreement

Participants generally agree that indium is the most likely candidate based on the calculations, though the discussion does not explicitly resolve any uncertainties regarding the method or assumptions used.

Contextual Notes

The discussion relies on the assumption that the electrolysis process is ideal and that the calculated values accurately reflect the properties of the metal ions involved. There may be limitations in the precision of the molar mass values used for comparison.

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Homework Statement


A solution of a trivalent metal ion is electrolysed by a current of 5.0A for 10 minutes during which time 1.18g of metal was plated out. The identity of the metal is:

A cobalt
B chromium
C indium
D gallium
E bismuth

Relative atomic masses:
1 faraday = 96,486 coulombs.

Homework Equations


current*time=coulombs
coulombs/96486=faraday
1 faraday = 1 mol of electrons

The Attempt at a Solution


5.0*10*60=3000 coulombs
3000/96486=0.031092 mol of electron

Since trivalent metal ion, mol of metal = 0.031092/3 = 0.010364 mols

Trial and error by dividing 1.18 by molar mass shows indium is closest. 1.18/114.82 = 0.1028. Is this the correct answer?

Cheers!
 
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Yes, indium sounds good.
 
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Thanks!
 
To avoid trial and error use this formula:

Molar mass (g/mol)=mass(g)/number of moles(mol)
M=m/n
M= 1.18g/ 0.010364 mol
M=113.86 g/mol

Cd
113.86-112.41=1.45 difference
Indium
114.82-113.86=0.96 difference

So the closest answer is Indium
 

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