Question

When vinegar is added to a solution of sodium bicarbonate, the mixture immediately begins to bubble furiously. As ime passes, however, there is less and less bubbling. Explain why this happens.

Short answer

Bubbling decreases because the reactants (vinegar and sodium bicarbonate) are consumed, lowering their concentration and slowing the reaction until the reactants are depleted, stopping the reaction.

Step-by-step solution

Identify the Chemical Reaction

Recognize that when vinegar (acetic acid) is added to sodium bicarbonate (baking soda), a chemical reaction occurs. The reaction releases carbon dioxide gas, which causes the bubbling.

Understand the Reactants Consumption

Understand that as the reaction progresses, the reactants (vinegar and sodium bicarbonate) are consumed to form the products (carbon dioxide gas, water, and sodium acetate).

Acknowledge the Decrease in Reaction Rate

As the reactants are consumed, there are fewer molecules available to react. This decrease in concentration of reactants leads to a slower rate of reaction and thus less bubbling over time.

Conclusion of the Reaction

Eventually, one or both of the reactants will be entirely consumed. At this point, the reaction stops, and bubbling ceases completely.

Key concepts

Acid-Base Reactions

In the realm of chemistry, acid-base reactions are a central concept and can be fascinating to explore. They involve the transfer of protons (H+) between a proton donor, known as the acid, and a proton acceptor, referred to as the base. Let's take the household example where vinegar, an acidic substance with acetic acid as its active component, is mixed with sodium bicarbonate, a basic compound. When these two react, the acid (vinegar) donates a proton to the base (sodium bicarbonate), resulting in the formation of carbon dioxide gas, water, and another compound called sodium acetate.

This effervescent reaction is quite visible and exciting as it produces the familiar bubbling we observe. However, this isn't just magic; it's science in action. In the case of the exercise, the fizzling is actually carbon dioxide escaping as gas – a hallmark of many acid-base reactions. Understanding this specific reaction helps grasp the broader concept of acid-base reactions and their role in everyday chemicals and even biological systems.

Reaction Rate

The rate of a chemical reaction dictates how quickly reactants are transformed into products. It's influenced by several factors including temperature, concentration of reactants, and the presence of a catalyst. In the context of the vinegar and sodium bicarbonate reaction, as the ingredients mix, the initial concentration of reactants is high, leading to vigorous bubbling due to rapid production of carbon dioxide. However, as the reaction moves forward, the amount of reactants decreases as they are converted into products.

When the concentration falls, there are fewer reactant molecules to collide with each other and thus, the frequency of effective collisions that lead to products diminishes. Consequently, the reaction rate slows down, and the bubbling becomes less intense. To improve your comprehension of this concept, it can be beneficial to visualize or even conduct the reaction, noting how the intensity of bubbling changes over time, reflecting the reaction rate at different stages.

Stoichiometry

Stoichiometry is a vital concept in chemistry that involves the calculation of reactants and products in chemical reactions. It is based on the conservation of mass and the law of definite proportions, which dictate that elements in a chemical reaction rearrange but are neither created nor destroyed. Essentially, stoichiometry tells you the quantitative relationships between the substances involved in a reaction.

Take our bubbling vinegar and sodium bicarbonate reaction; by using stoichiometry, one can precisely calculate how much vinegar is needed to react with a certain amount of sodium bicarbonate. This also means that you can predict when the reaction will stop. When either of the reactants is used up, the reaction halts – no more carbon dioxide, no more bubbles. With the principles of stoichiometry, you'll understand not just the 'if' of reactions, but the specific 'how much' and 'how long', which is essential in everything from baking to pharmaceuticals.