Chemistry Study Guide Acids And Bases
What are Acids and Bases? Each food we eat tastes different, and there are many reasons for that: substances can be sweet, spicy, bland, bitter, or acidic. Understanding why things taste the way they do is pretty complicated.
But there's one part of it that simpler: acidity. Whether it's foods you eat, or cleaning products around your house, every substance is either an acid, a base, or neutral. But what those terms mean? Bottle of hydrochloric acid used in a science lab An acid is a chemical that is sour tasting and corrosive. Strong acids can dissolve metals, and neutralize bases.
Chemically, they have to contain positive hydrogen ions. A base on the other hand is a chemical that is a bitter tasting and caustic. Bases can neutralize acids, and chemically they contain hydroxide ions (negative ions made up of an oxygen and hydrogen atom bonded together). A neutral substance is something right in the middle - is not quite an acid, and not quite a base.
Acids are corrosive We measure acids and bases on a scale called the pH scale, where 7 is neutral, a pH larger than seven is a base, and a pH smaller than seven is an acid. This can be tested using something called indicator paper, which turns different colors depending on pH: red for acid, blue for a base, and green for neutral.
So that's the difference between acids, bases, and neutral substances. But what are examples of each of these?
What common substances we find in our daily lives are acids and bases? Let's take a look.
Common Acids and Bases We said that acids are sour and corrosive, so that includes things like lemon juice (with a pH of 2) and vinegar (with a pH of 3). But contrary to popular belief, even milk is slightly acidic. There are also lots of household products that are acidic, like floor cleaners and toilet bowl cleaners, which tend to have a pH between zero and three. However cleaning products are more likely to be bases, since the caustic properties of bases can be useful. One of the strongest examples is chlorine bleach, which has a pH between 11 and 13, and ammonia which has a pH between 11 and 12. But baking soda is also a base (with a pH of around 9), as is dish soap (7-8).
When it comes to food, bases are things like egg whites (8.5), and some vegetables like spinach, garlic, and broccoli, though all foods that are bases are not strong bases. Chart showing examples of acids and bases. When it comes to neutral substances, the best example is water. But there are a few other examples like vegetable oil, table salt, and blood.
Generally, very weak acids and bases are hardly different from usual substances. So you could argue that even milk and egg whites are pretty close to neutral.
So next time you see one of the substances, or eat a particular food, maybe you'll know whether it's an acid or base. If you don't, you can always get some indicator paper and find out for yourself. Lesson Summary Substances can be separated into acids, bases, and neutral substances.
Acids are sour and corrosive, turn indicator paper red, and have a pH smaller than 7. Bases are bitter and caustic, turn indicator paper blue, and have a pH larger than 7. Neutral substances have no particularly strong taste, turn indicator paper green, and have a pH of 7. Acids contain positive hydrogen ions, and bases contain negative hydroxide ions. When you mix an acid and base together, they neutralize each other and their pH moves closer to 7.
Examples of acids include vinegar, toilet bowl cleaners, lemon juice, and soda. Examples of bases include egg whites, spinach, and chlorine bleach. Examples of neutral substances include water, vegetable oil, table salt, and blood.
Figure%: The Arrhenius model of acids and bases, where A = acid and B = base At the time that Arrhenius proposed these definitions, water was virtually the only solvent used in chemistry, and nearly all known acids and bases contained protons (H +) and hydroxyl groups (OH), respectively. His definition was sufficient for the chemistry that was understood then. But progress in chemistry necessitated new definitions: it was discovered that ammonia behaves like a base, and HCl donates protons in non-aqueous solvents.
The Bronsted-Lowry model of acids and bases serves that need by describing acids as proton donors and bases as proton acceptors. These definitions remove the role of solvent and allow bases like ammonia and fluoride ion to be classified as bases, so long as they bond to protons. The Bronsted-Lowry model implies that there is a relationship between acids and bases (acids transfer protons to bases) and allows us to define conjugate acids and conjugate bases, as seen in. Figure%: The Bronsted model of acids and bases You should note in the figure above that the conjugate acid of the base, BH +, acts as an acid in the reverse reaction by donating a proton to the conjugate base, A -, of the acid HA. Despite the usefulness of the Bronsted-Lowry definition, there is an even more general definition of acids and bases provided by G.
Chemistry Chapter 18 Study Guide Acids And Bases
Acids And Bases Wikipedia
The Lewis model of acids and bases proposes that an acid is an electron pair acceptor while a base is an electron pair donor. This model of acidity and basicity broadens the characterization of acid-base reactions to include reactions like the following which do not involve any hydrogen transfers. The nitrogen atom in ammonia donates an electron pair to complete the valence octet of boron.