Question

Which of the following is not a use of baking soda? (a) In medicines as antacid. (b) As a component of baking powder. (c) In removing permanent hardness of water. (d) In fire extinguishers.

Short answer

The incorrect use of baking soda is (c) In removing permanent hardness of water.

Step-by-step solution

Understanding the uses of Baking Soda

Identify the common uses of baking soda (sodium bicarbonate), which include its role as an antacid, a leavening agent in baking (as a component of baking powder), water softener for removing permanent hardness of water, and as a fire extinguishing medium.

Identifying the Incorrect Use

Compare the given options with the known uses of baking soda to identify the option that does not match its standard applications.

Selecting the Correct Answer

Option (c) is not a typical use of baking soda, as it is not commonly used to remove permanent hardness of water, that is more typically a function of washing soda (sodium carbonate), not baking soda (sodium bicarbonate).

Key concepts

Understanding Baking Soda as an Antacid

Baking soda, or sodium bicarbonate, is much more than a kitchen staple; it's a multitasking wonder with a diverse range of uses. One notable application is its role as an antacid. When bicarbonate ions from the baking soda mix with stomach acid, a chemical reaction occurs that neutralizes the acid, thereby relieving discomfort from indigestion and heartburn.

To elaborate, our stomach acid has a low pH, indicating high acidity. When sodium bicarbonate enters the stomach and comes into contact with this acid, the reaction produces carbon dioxide gas and water. This process can be expressed by the following chemical equation:
\[ \text{NaHCO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O} + \text{CO}_2(g) \]
The generation of carbon dioxide contributes to burping, which can release some of the pressure and discomfort associated with indigestion. It is essential, however, for students to understand that only a proper dosage can be effective and safe. Overuse or incorrect use of baking soda can lead to serious electrolyte and acid/base imbalances.

Baking Soda in Baking Powder

The magic of baking is often attributed to this unassuming white powder—baking soda. As a key ingredient in baking powder, baking soda helps baked goods rise and achieve the desired texture. The function of baking powder as a leavening agent is to produce carbon dioxide when it reacts with moisture and an acid.

Baking powder consists of three components: an acid (such as cream of tartar), a base such as sodium bicarbonate, and a buffering material to prevent the acid and base from reacting too early. When wet ingredients are combined with baking powder, the acid-base reaction produces carbon dioxide bubbles, which are trapped by gluten in the dough or batter. As these bubbles expand during baking, they cause the dough to rise, resulting in light and fluffy cakes, bread, and other baked goods.

Understanding the role of each component in baking powder can aid students in effectively leveraging its properties in recipes and perhaps even creating their own baking powder mixtures by combining the appropriate ratios of an acid, base, and buffer.

The Role of Baking Soda in Fire Extinguishers

Baking soda's properties are not just limited to the kitchen or medicine cabinet—it also plays a crucial role in fire safety. Sodium bicarbonate is a common component in dry chemical fire extinguishers, particularly those classified as Class B and C extinguishers, which are suitable for putting out fires that involve flammable liquids or gases and electrical equipment.

The mechanism by which baking soda extinguishes fires is twofold. Firstly, when baking soda is heated, it releases carbon dioxide gas. Since CO2 is heavier than oxygen, it blankets the fire, cutting off the oxygen supply the fire needs to continue burning. The chemical equation for this decomposition is:\[ 2\text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2 \]
Secondly, the baking soda also helps to cool the fire, as the endothermic reaction absorbs heat. Both effects contribute to the suppression of the fire, making baking soda-based extinguishers an effective and safe option for tackling certain types of fires. Learning how this chemical reaction helps in extinguishing fires not only enriches students' understanding of chemistry but also serves as a practical life-saving application of science.