In the reaction
`3Br_2 + 6CO_3^(2-) + 3H_2O to 5Br^(-) + BrO_3^(-) + 6HCO+_3^(-)`

Options

A. bromine is oxidised and carbonate is reduced
B. bromine is both reduced and oxidised
C. bromine is neither reduced nor oxidised
D. bromine is reduced and water is oxldised

Explanation

To analyze the given reaction and determine the oxidation states of bromine, we can follow these steps:

### Step 1: Identify the Reactants and Products
The reaction is:
\[ 3Br_2 + 6CO_3^{2-} + 3H_2O \rightarrow 5Br^{-} + BrO_3^{-} + 6HCO_3^{-} \]

### Step 2: Determine the Oxidation States of Bromine
- In \(Br_2\), the oxidation state of bromine is **0** (elemental form).
- In \(Br^{-}\), the oxidation state of bromine is **-1**.
- In \(BrO_3^{-}\), we can calculate the oxidation state of bromine:
- Let the oxidation state of Br be \(x\).
- The overall charge of the ion is -1.
- The oxidation states of oxygen are -2 (3 oxygen atoms contribute -6).
- Therefore, we have:
\[ x + 3(-2) = -1 \implies x - 6 = -1 \implies x = +5 \]
Thus, the oxidation state of bromine in \(BrO_3^{-}\) is **+5**.

### Step 3: Analyze the Changes in Oxidation States
- From \(Br_2\) (0) to \(Br^{-}\) (-1): This indicates a **reduction** (gain of electrons).
- From \(Br_2\) (0) to \(BrO_3^{-}\) (+5): This indicates an **oxidation** (loss of electrons).

### Step 4: Conclusion
Since bromine undergoes both reduction (to \(Br^{-}\)) and oxidation (to \(BrO_3^{-}\)), we conclude that bromine is both reduced and oxidized in this reaction.

### Final Answer
The correct option is **B: bromine is both reduced and oxidized**.

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