What is the change in oxidation number of carbon in the following reaction?
`CH_4 (g) + 4Cl_2(g) rarr CCl_4(l) + 4HCl(g)`

Options

A. 4 to 4
B. 0 to 4
C. -4 to +4
D. 0 to -4

Answer

To determine the change in oxidation number of carbon in the reaction:

\[ CH_4 (g) + 4Cl_2(g) \rightarrow CCl_4(l) + 4HCl(g) \]

we will follow these steps:

### Step 1: Determine the oxidation state of carbon in methane (CH₄).
In methane (CH₄), hydrogen has an oxidation state of +1. Since there are four hydrogen atoms, the total contribution from hydrogen is:

\[ 4 \times (+1) = +4 \]

Let the oxidation state of carbon be \( x \). The overall charge of the molecule is zero, so we can set up the equation:

\[ x + 4 = 0 \]

Solving for \( x \):

\[ x = -4 \]

Thus, the oxidation state of carbon in CH₄ is -4.

### Step 2: Determine the oxidation state of carbon in carbon tetrachloride (CCl₄).
In carbon tetrachloride (CCl₄), chlorine has an oxidation state of -1. Since there are four chlorine atoms, the total contribution from chlorine is:

\[ 4 \times (-1) = -4 \]

Let the oxidation state of carbon be \( y \). Again, the overall charge of the molecule is zero, so we can set up the equation:

\[ y - 4 = 0 \]

Solving for \( y \):

\[ y = +4 \]

Thus, the oxidation state of carbon in CCl₄ is +4.

### Step 3: Calculate the change in oxidation state of carbon.
Now, we can calculate the change in oxidation state of carbon from CH₄ to CCl₄:

Initial oxidation state of carbon in CH₄: -4
Final oxidation state of carbon in CCl₄: +4

Change in oxidation state:

\[ \text{Change} = +4 - (-4) = +4 + 4 = +8 \]

### Conclusion:
The change in oxidation number of carbon in the given reaction is +8.

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