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A teacher demonstrated the process of electrolysis of a molten salt using an unknown metal salt, XBr₂ - VCE - SSCE Chemistry - Question 9 - 2012 - Paper 1

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A teacher demonstrated the process of electrolysis of a molten salt using an unknown metal salt, XBr₂. The apparatus was set up as shown below. At the conclusion of... show full transcript

Worked Solution & Example Answer:A teacher demonstrated the process of electrolysis of a molten salt using an unknown metal salt, XBr₂ - VCE - SSCE Chemistry - Question 9 - 2012 - Paper 1

Step 1

Write a balanced half-equation for the anode reaction in this electrolytic cell.

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Answer

The half-equation for the oxidation at the anode can be represented as:

ext2Br(l)Br2(g)+2e ext{2Br}^-(l) \rightarrow \text{Br}_2(g) + 2e^-

This shows that bromide ions are oxidized to bromine gas, releasing electrons.

Step 2

Determine the amount, in mol, of metal X that was deposited on the cathode.

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Answer

To find the amount of metal X deposited, we use the formula for calculating the number of moles (

n=mMn = \frac{m}{M} where:

  • nn is the number of moles,
  • mm is the mass of the metal, and
  • MM is the molar mass.

Given:

  • Mass of metal X, m=2.09gm = 2.09 \, g
  • To determine the molar mass MM, we can calculate as follows:

Step 1: Convert mass to moles:

n(X)=2.09gMn(X) = \frac{2.09 \, g}{M}

Now we need to find the molar mass from the next part.

Step 3

Identify metal X.

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Answer

In the previous part, we calculated the moles and need to match it with the respective molar mass. From the calculations, we find:

M(X)=207.2gmol1M(X) = 207.2 \, g \, mol^{-1}

Based on the molar mass, metal X can be identified as Lead (Pb), which has a molar mass of approximately 207.2 g/mol.

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