When you combine lemon juice, which is acidic (primarily citric acid), with baking soda (sodium bicarbonate, a base), a chemical reaction occurs that produces carbon dioxide gas (CO₂), water, and sodium citrate. The fizzing and bubbles you see are due to the release of carbon dioxide gas during this reaction.
The chemical properties of the gas formed (carbon dioxide) differ from those of baking soda and lemon juice in several ways:
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Nature of the Substance:
- Lemon Juice: Contains citric acid and other compounds, making it acidic. It has a low pH (typically around 2-3).
- Baking Soda: A basic compound (sodium bicarbonate) that reacts with acids. It has a higher pH (around 8-9).
- Carbon Dioxide Gas: Is a neutral gas at room temperature and pressure. It does not exhibit acidic or basic properties in the same way that lemon juice or baking soda does.
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Reactivity:
- Lemon juice is reactive as it can donate protons (H⁺ ions) due to its acidity.
- Baking soda reacts with acids to release CO₂ and neutralize the acid.
- Carbon dioxide itself is relatively inert under normal conditions and does not react further like its precursors.
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Phase:
- Lemon juice and baking soda are both in liquid (aqueous) and solid forms, respectively, before the reaction.
- Carbon dioxide gas is in the gaseous state and expands into the air, which is a different phase with different properties compared to the reactants.
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Density and Behavior:
- Lemon juice and baking soda have a specific density that is significantly higher than that of carbon dioxide gas, which is lighter than air and will rise when produced.
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Taste and Smell:
- Lemon juice has a sour taste and distinctive citrus aroma due to its organic compounds.
- Baking soda is generally tasteless in small quantities but can impart a slight alkaline taste.
- Carbon dioxide is tasteless and odorless.
In summary, the carbon dioxide produced differs fundamentally from lemon juice and baking soda in terms of its chemical nature, reactivity, phase, and sensory properties.