Is baking soda a pure substance or a mixture?
The Correct Answer and Explanation is:
Correct Answer:
Baking soda is a pure substance.
Explanation:
Baking soda, chemically known as sodium bicarbonate (NaHCO₃), is considered a pure substance because it has a definite and uniform composition throughout. A pure substance consists of only one type of particle and has fixed chemical and physical properties. In the case of baking soda, it is composed entirely of sodium bicarbonate molecules, each consisting of one sodium (Na), one hydrogen (H), one carbon (C), and three oxygen (O) atoms bonded in a specific ratio and structure.
Unlike mixtures, which contain two or more substances physically combined and can vary in composition, a pure substance like baking soda has a consistent chemical formula. It cannot be separated into other substances by physical methods such as filtration or evaporation. Only chemical reactions can alter its composition.
Baking soda appears as a white crystalline powder that is soluble in water. Its chemical identity does not change regardless of its physical state or how finely it is ground. This distinguishes it from mixtures like air or salt water, where different components coexist without bonding chemically.
In everyday use, baking soda is often found in household products and used in cooking, cleaning, and deodorizing. Despite this, the product labeled as “baking soda” in stores typically contains nearly 100% pure sodium bicarbonate without any added ingredients, further supporting its classification as a pure substance.
Chemically, baking soda is classified as a base. It reacts with acids to produce carbon dioxide gas, water, and a salt. This reaction is the basis for its role in baking, where it helps dough rise. Its consistent reactivity is another indication of its purity. A mixture would not behave as predictably or uniformly.
Therefore, based on its fixed composition, consistent properties, and chemical identity, baking soda qualifies as a pure substance.
