Acids Bases Goals To determine the difference between
Acids & Bases
Goals • To determine the difference between Acids & Bases • Discuss the importance of studying Acids & Bases
HCl(g) Na. OH(s) When an IONIC compound is placed in water, it will break apart into two ions. If one of those ions is H+. . . The solution is acidic. If one of the ions is OH-. . . The solution is basic.
Acidic solution Alkaline solution
Formulas - Acids • In general, acids are identified by the hydrogen in the front of its chemical formula. For example, the formula for hydrochloric acid is HCl • Others are: Sulfuric acid H 2 SO 4; Carbonic acid H 2 CO 3; and nitric acid HNO 3. • Some exceptions to this rule are some organic acids —such as acetic acid (CH 3 COOH)—have their formulae designated according to their structure.
Formulas - Bases • Bases can often be identified by the OH term in the end of their chemical formula, as seen in sodium hydroxide Na. OH, magnesium hydroxide Mg(OH)2 and potassium hydroxide KOH. • There are some exceptions to this rule: ammonia gas NH 3 • Some organic acids have formulae that make them look like bases. Acetic acid (CH 3 COOH) for example.
The Arrhenius theory: • Acids dissolve in water to produce hydrogen ions, H+ (more corrrectly, the hydronium ion H 3 O+) • Bases produce the hydroxide , OH- ions. • This theory, while essentially correct, has been superseded by the Brønsted. Lowry theory
Characteristics - differences Acids Bases • Tastes sour • Turns litmus paper red • React with some metals to give off H 2 gas. • React with carbonates to produce CO 2 gas • p. H of 0 – 7 • Have an excess of H+ ions in solution. • Tastes bitter • Turns litmus paper blue • Feels slippery to the touch • p. H of 7 to 14 • Have an excess of OH- ions in solution.
Characteristics - similarities • Both conduct electricity • Acids and bases react together to form salts and water only. The process is called neutralization Na. OH + HCl H 2 O + Na. Cl • Both acids and alkalis cause colour changes in certain substances called indicators, such as litmus:
Identifying Acids and Bases • Acids have a ph from 0 -7 • Lower p. H value indicates a stronger acid. • Bases have a p. H from 7 -14 • Higher p. H value indicates a stronger base.
Definitions of Acids and Bases • An acid is a substance that breaks into ions in an aqueous solution. • A Base (alkaline) is a substance that breaks into ions in an aqueous solution. • Note: aqueous solution is any solution where is the solvent.
Characteristics Of Acids can be characterized by: 1. A sour taste. 2. It turns blue litmus paper red 3. It tastes sour. Try drinking lemon juice (citric acid)
Characteristics of Bases A Base is characterized by: 1. A bitter taste. (Milk of Magnesia) 2. It feels slippery. (Soapy Water) 3. It turns Red Litmus Blue.
Mini-quiz to check your understanding • Water 1. What element is in most acids • Hydrogen and bases? • Sulfur
2. Which p. H indicates the material is acidic? • 5. 0 • 7. 0 • 9. 0
3. Why should you be careful dealing with acids? • They can eat your skin away • They can cause an upset stomach • They smell real bad
5. Which is a base? • CH 3 COOH • Na. Cl
6. What can a gardener do if the soil is too acidic? • Add a base such as lime or chalk to reduce acidity • Add lemon juice to reduce the acidity • Add salt (Na. Cl) until the soil becomes a base
What is the p. H scale? • The p. H scale measures how acidic or basic a solution is.
The p. H scale • The p. H scale is the concentration of hydrogen ions in a given substance. • “the power of Hydrogen”
Did we Miss something? ? • What happens when the p. H of a substance is 7? • Ans: A p. H level of 7 indicates a Neutral Substance i. e: Water!
Test Your Knowledge • What is the range of an ACID on the p. H scale? Ans: 0 -7 • What is the range of a BASE and what is another name for a BASE? Ans: 7 -14, Alkaline
Why Learn about Acids & Bases? • What do you think is the p. H level of Toronto tap water? • The p. H of a swimming pool must be checked periodically. Why? • Is it important for Lakes & Rivers to maintain a certain p. H?
Naming Acids • • • Binary acids HF hydrofluoric acid HBr Hydrobromic acid HI HCl
• • Acids with polyatomic ions H 2 SO 4 Sulphuric acid HNO 3 Nitric Acid H 2 CO 3 Carbonic Acid
Acid-Base Indicators • Certain chemicals have the special property of appearing in different colours depending on the p. H of the solution they are in. • Such chemicals are known as acid-base indicators • A couple of drops of indicator in a solution will indicate its p. H.
Three commonly used indicators.
Neutralization Reactions • What would happen if an acid and a base were mixed up? • What would happen if a hydrogen ion (H+) from an acid reacted with a hydroxide ion (OH-) from a base?
Neutralization - reaction of an acid and base forming a salt and water. HCl + Na. OH Na. Cl + HOH Salts - composed of the positive half of a base and the negative half of an acid. Question: What acid and base react to produce each of these salts? Ca. SO 4 NH 4 NO 3 Ca. Cl 2
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