‘What is the oxidation state of carbon in baking soda (aka; sodium hydrogen carbonate or sodium bicarbonate)?’
The correct answer and explanation is:
The oxidation state of carbon in baking soda (sodium hydrogen carbonate, NaHCO₃) is +4.
Explanation:
To determine the oxidation state of carbon in sodium bicarbonate (NaHCO₃), we first assign oxidation states to all the elements based on known rules:
- Sodium (Na): Sodium is an alkali metal, and alkali metals always have an oxidation state of +1 in compounds.
- Hydrogen (H): In most compounds, hydrogen has an oxidation state of +1.
- Oxygen (O): Oxygen typically has an oxidation state of -2, except in peroxides or when bonded to fluorine.
- Carbon (C): This is the element we need to determine the oxidation state for.
The formula of sodium bicarbonate is NaHCO₃, which means it contains one sodium ion (Na⁺), one hydrogen ion (H⁺), one carbonate ion (CO₃²⁻), and three oxygen atoms.
The sum of the oxidation states of all elements in a neutral molecule must be zero. Let’s break it down step by step:
- The oxidation state of Na is +1.
- The oxidation state of H is +1.
- The oxidation state of O is -2, and since there are three oxygen atoms in the carbonate ion (CO₃²⁻), the total oxidation state contribution from oxygen is 3 × (-2) = -6.
- The carbonate ion (CO₃²⁻) has an overall charge of -2. To balance the total charge, the oxidation state of carbon must be +4.
So, the oxidation states are as follows:
- Na = +1
- H = +1
- C = +4
- O = -2 (for each oxygen atom)
When added together: +1 (Na) + 1 (H) + 4 (C) + (-6) (O) = 0, which confirms that the compound is neutral.
Thus, the oxidation state of carbon in sodium bicarbonate is +4.