Have you ever followed a recipe to make baked goods such as a cake or bread? You have probably seen baking soda on the list of ingredients and perhaps you have wondered why it is needed. Baking soda is a leavening agent, which means it causes a chemical reaction to occur that causes the baked good to rise.
The texture of bread (and even cake) can be quite holey. You may have noticed that there are usually holes of various sizes found once you cut into breads and cakes. These holes are formed from carbon dioxide bubbles produced in the reaction between baking soda and an acidic ingredient of the recipe. This causes the dough to rise (become larger in size) and leaves behind pockets, or holes, when baked.
Here we see the cook holding a spoonful of baking soda (sodium bicarbonate, \(\text{NaHCO}_{3}\)) and adding vinegar (acetic acid, \(\text{HC}_{2}\text{H}_{3}\text{O}_{2}\)) to produce a white foam that is added to the recipe. This white foam is a combination of carbon dioxide (\(\text{CO}_{2}\)) bubbles, water (\(\text{H}_{2}\text{O}\)), and sodium acetate solution (\(\text{NaC}_{2}\text{H}_{3}\text{O}_{2}\)).
We can represent this chemical reaction by a chemical equation that shows the chemical formulas for the reactants and the products:
\(\text{NaHCO}_{3(\text{s})} + \text{HC}_{2}\text{H}_{3}\text{O}_{2(\text{aq})} \rightarrow \text{CO}_{2(\text{g})} + \text{H}_{2}\text{O}_{(\text{l})} + \text{NaC}_{2}\text{H}_{3}\text{O}_{2(\text{aq})}\)
We can classify reactions by distinguishing among five types. Some reactions, such as this one, fit into more than one of these classes.
In this lesson, you will learn the characteristics of the five different classes of chemical reactions, classify chemical reactions according to their type, and predict the products of some chemical reactions.
Question
In the previous lesson, you learned that a chemical equation must be balanced to show that mass is conserved during a chemical reaction. How do you know the equation representing our example reaction is balanced?
In a balanced chemical equation, the number of atoms of all elements are equal on both sides of the arrow.
\(\ce{NaHCO3_{(s)} + HC2H3O2_{(aq)} -> CO2_{(g)} + H2O_{(l)} + NaC2H3O2_{(aq)}}\)
| Reactants | Products |
|---|---|
|
\(\ce{1 Na}\) \(\ce{5 H}\) \(\ce{3 C}\) \(\ce{5 O}\) |
\(\ce{1 Na}\) \(\ce{5 H}\) \(\ce{3 C}\) \(\ce{5 O}\) |
