Acids, Bases, and pH

Common examples: citrus fruits contain citric acid; apples contain malic acid; and grapes contain tartaric acid. When acids dissolve in water, they ionize, which means that they form ions. Acids

When acids ionize, they form hydrogen ions, which attach to water molecules to make hydronium ions, H3O+. Hydronium ions give acids their properties. Acids

Properties include: taste sour, cause indicators to change color, and conduct electric current. They are also corrosive and can damage materials, including your skin. Acids

Acids Strong acids ionize completely when they are dissolved in water. A substance that conducts electricity when dissolved in water is an electrolyte. A weak acid does not ionize completely in water. Acids

Strong acids = Hydrochloric acid HCl, Sulfuric acid H2SO4, Nitric acid HNO3. Weak acids = Acetic acid CH3COOH, Formic acid HCOOH, Citric acid H3C6H5O7. Acids

Acids are used in many manufacturing processes and are necessary in many organisms. Strong acids are corrosive and can damage living tissue. For example, your stomach normally contains a dilute solution of hydrochloric acid that helps you digest food. Acids

Acids Even weak acids are not always safe to handle. Vinegar is a 5% solution of acetic acid in water, but acetic acid can damage the skin. The vapors are harmful to the eyes, mouth, and lungs. Acids

Properties include: bitter taste, slippery feeling, conduct electric current, cause indicators to change color, and can damage the skin. When bases dissolve in water, they form hydroxide ions, OH-. Bases

Some basic compounds contain hydroxide ions, but others react with water molecules to form hydroxide ions. The hydroxide ions cause red litmus paper to turn blue. Bases

Strong bases produce as many ions as possible when dissolved in water. Strong bases are ionic compounds that contain a metal ion and a hydroxide ion (metal hydroxides). NaOH is an example of a metal hydroxide that can be found in drain cleaners. Bases

Some metal hydroxides such as calcium hydroxide and magnesium hydroxide, are not very soluble in water. However, they are still strong bases because of all the ions that do dissolve separate. The strength of an acid or base does not depend on the concentration of the solution. Bases

Bases Weak bases like ammonia, NH3, do not contain hydroxide ions. However, it forms hydroxide ions when dissolved in water through an ionization process. Bases

Strong bases = Potassium hydroxide KOH, Sodium hydroxide NaOH, Calcium hydroxide Ca(OH)2. Weak bases = Ammonia NH3, Methylamine CH3NH2, Aniline C6H5NH2. Bases

You can tell if a solution is acidic or basic by using an indicator such as litmus paper. The pH of a solution indicates the concentration of H3O+ ions. In solutions, the concentration of hydronium ions is related to the concentration of hydroxide ions, OH-. The pH of a solution also indicates the concentration of OH- ions. pH

pH The acidity or basicity of a solution is often critical. Enzymes in your body will not work if your blood is too acidic or basic. A pH value can tell you how acidic or basic a solution is, and can tell you if the solution is neutral. pH

pH The scale ranges from 0-14. 0-6.99 pH is acidic. 7 pH is neutral. 7.1-14 pH is basic. pH

The concentration of a substance in a solution is often described by molarity (M), or the number of moles of the substance per liter of solution. The hydronium ion concentration of pure water is 0.0000001 mol/L, or 1 x 10 -7 M. pH

The pH is the negative of the power of 10 that is used to describe the concentration of H3O+ ions. So the pH of pure water is 7. pH

Example: Determine the pH of a 0 Example: Determine the pH of a 0.0001 M solution of the strong acid HCl. pH

pH Small differences in pH mean large differences in acidity. For example, the pH of apple juice is about 3, and the pH of coffee is about 5. This difference of two pH units means that apple juice is 102, or 100 times, as acidic as coffee. pH