Acids, Bases and Salts Test on Friday May 10

Acids A substance that produces hydrogen ions (H+) in a water solution. When acids are mixed with water, the H+ ions from the acid react with H2O to form H3O+ ions. These are called hydronium ions.

Properties of Acids Sour taste Corrosive React with indicators to produce color changes An indicator is an organic compound that changes color in acid and base.

Common Acids Citric Acid – found in fruit Lactic Acid – found in yogurt and milk Acetic Acid – vinegar Hydrochloric Acid – stomach acid

Bases A substance that forms hydroxide ions (OH-) in the presence of water. A substance that accepts H+ ions from acids

Properties of Bases Slippery Texture Bitter Taste Reacts with indicator to produce a change in color.

Common Bases Cleaning supplies Antacids Soap Fertilizer

Solutions Dissociation of Acids When an acid is placed in water, the acid separates into ions This is called dissociation. The hydrogen ions combine with water to make hydronium ions.

Solutions Dissociation of Bases When bases are placed in water: The base dissociates (separates into ions) Unlike acids, the ions from the base do not combine with the water molecules.

Ammonia Almost all the bases contain OH in their chemical formula. Ammonia is the exception. Ammonia is NH3. Instead of separating to form a hydroxide ion, it steals a hydrogen from water and turns water into a hydroxide ion.

Did you Pay Attention? When acids are dissolved in water, what ion do they form? When bases are dissolved in water, what ion do they form? What is an indicator? How does Ammonia make a hydroxide ion?

Acid Strength Acid strength is determined by how much of the acid ionizes in water. In a strong acid, almost all of the acid molecules separate into ions. Strong acids conduct electricity. In a weak acid, only part of the acid molecules separate into ions.

Base Strength Base strength is determined by how much of the base dissociates in water. In a strong base, almost all of the base molecules separate into ions. Strong bases conduct electricity. In a weak base, only part of the base molecules separate into ions.

Strength and Concentration Strength and Concentration are not the same thing. Strength refers to how easily the acid or base dissociates. Concentration refers to how much acid you have per liter of water. (Like dilution) A small amount of a strong acid in a large amount of water is still a strong acid, but it is very dilute.

pH Scale The pH of a solution is a measure of the concentration of H+ ions in the solution. Acids have a pH less than 7, the more acidic something is, the smaller its pH will be. Bases have a pH greater than 7, the more basic something is, the bigger its pH will be. Water and other neutral substances have a pH equal to 7.

Buffers Buffers are solutions containing ions that react with additional acids or bases to minimize the effects on pH.

Acid + Base  Salt + Water Neutralization A neutralization reaction is a chemical reaction between an acid and a base that takes place in water. Acid + Base  Salt + Water

Salts A salt is a compound that is formed when the negative ions from an acid combine with the positive ions from the base. Salts also form when an acid reacts with a metal. Salt is an essential mineral for animals. Other uses include paint, rubber, soap, detergents and dry cell batteries.

Titration A solution of known concentration is used to determine the concentration of an unknown solution. The solution that has a known concentration is called the standard solution. One of the solutions is an acid and the other solution is a base.

Titration Steps Add a few drops of acid/base indicator to the unknown solution. Slowly add the known concentration to the unknown concentration until the end point is reached. The endpoint is reached when the unknown solution changes colors and does not return to the original color.

Soaps Soaps are organic salts with polar and nonpolar ends. The nonpolar hydrocarbon end interacts with oil and dirt. The polar end helps oil and dirt dissolve in water.

Problem with Soaps Some water (hard water) causes the Na or K atom to be replaced with another atom. When this happens the soap doesn’t dissolve and soap scum develops Detergents were developed to prevent soap scum.

Detergents Synthetic Form more soluble salts with the ions in hard water and reduce soap scum Can cause environmental problems like foam

Esters The organic counterpart of salts Esters are formed from acids and alcohols with a hydroxyl Esters are used to produce fruit flavors and smells Many esters in a chain make polyesters which are synthetic fibers used in fabric.