Note Guide 5-1 – Acids and Bases

Note Guide 5-1 – Acids and Bases Identifying Acids --acid is a compound that produces hydronium ions (H30+) when dissolved in water. --Properties of acids include 1. Sour taste: foods like lemons, grapefruits, limes contain citric acid. Vinegar contains acetic acid 2. Reactivity with metals: aluminum foil can react with the citric acid from a tomato. --reaction between an acid and a metal is an single-replacement reaction (chemical reaction in which one element takes the place of another element in a compound Zn + 2HCl  H2 +ZnCl2  Means reacts to produce

3. Color changes in Indicators Indicator – is any substance that changes color in the presence of an acid or base Ex: Litmus paper --blue litmus paper turns red when in acid so, if an unknown solution is placed on blue litmus paper and it turns red, its an acid. Common Acids --acetic acid – vinegar --carbonic acid – Carbonated beverages --Nitric acid – Fertilizer --Sulfuric acid – Car batteries

Identifying Bases --Base= compound that produces hydroxide ions (OH-) when dissolved in water Properties of Bases include 1. Bitter taste: unsweetened chocolate, cough syrups, etc NaOH  Na+ + OH- 2. Slippery feel: wet soap, cleaning products; 3. Color changes: turns red litmus blue --so if an unknown solution turns a piece of red litmus blue, it’s a base Common bases: --Aluminum hydroxide = deodorant, antacid --Calcium hydroxide = concrete, plaster --Magnesium hydroxide = antacid, laxative

Neutralization and Salts: --A reaction between an acid and a base is called neutralization --basically cancels each other out. --negative ions from acid combine with positive ions of base to produce ionic compound called salt --the neutraliztion reaction between an acid and a base produces a salt and water (H3O++ Cl-) + (Na+ + OH-)  2H20 + (Na+ + Cl-) (acid) (base) (water) (salt) Common Salts --sodium chloride = food flavoring --Magnesium chloride = de-icer for roads --Calcium carbonate = chalk, marble floors, and tables --Ammonium nitrate = fertilizer, cold packs

Note Guide 5-2 Strength of Acids and bases --How can you describe the acidity or basicity of a solution? By using a number scale from 0 to 14 to describe the concentration of hydronium ions (H3O+) in a solution. This scale is the pH scale. The pH measure how much hydronium ions are in the solution --if a solution measure to a 7, then it is neutral (not acid or base) --if a solution measures over a 7, it is a base --if a solution measures under a 7, it is an acid –see figure 22 on page 247 So what does this mean in regard to hydronium concetration? --the lower the pH value, the greater the H3O+ ion concentration in solution --the higher the pH value, the lower the H3O+ ion concentration in solution.

Strong Acids and Bases --when acids almost completely ionize (most molecules ionize) when dissolved in water, they are strong acids. --sulfuric and nitric acids -- when bases dissociate (seperation of ions as they dissolve) almost completely in water, they are considered strong bases. Weak acids and bases --weak acids and bases ionize (acids) or dissociate (bases) only slightly in water Weak Acids = citric acid in OJ and acids in vinegar Weak Bases = toothpase and shampoo Concentration vs. Strength…the same right?

NO! --concentration is amount of solute (substance whose particles are dissolved in a solution) dissolved in a given amount of solution --strength is the solute’s tendency to form ions in water. Do not assume that strong acids have a low pH because concentration also affects pH Buffers = solution that is resistant to large changes in pH. --Weak acids and bases are used to make buffers --Why does this work? Because the buffer reacts with both the acid and base, keeping the pH relatively constant Electrolytes: substance that ionizes or dissasociates into ions when it dissolves in water --sports drinks How do they work?Restore the balance of ions in body

Strong acids and bases are strong electrolytes because they dissociate or ionize almost completely --salts are strong electrolytes --batteries produce electricity which contain electrolytes --fuel cells pH scale

Note Guide 5-3 day 1 --if a compound contains carbon and hydrogen we call it an organic compound. They often combine with O and N --90% of all compounds are organic --carbon has 4 valence electrons which allows it to form many bonds to achieve stability. 4 single bonds, a double bonds, etc. --basically any combination of 4 to meet valence electrons • 3 forms of carbon • Diamond • Graphite • Fullerenes ( large hollow spheres or cages of carbon) found in meteorites

Saturated Hydrocarbons Hydrocarbon – organic compound that contains only the elements hydrogen and carbon Saturated hydrocarbon – all bonds are single bonds . These use the maximum amount of hydrogen atoms for each carbon atom Ex: methane Properties of a hydrocarbon are determined by 1.the number of carbon atoms –more carbon atoms, the higher the boiling point 2. the arrangement of the atoms 3 ways to arrange carbon • Straight chains (see figure 4 page 264)

2. Branched chains– (compare how butane to isobutane on page265) --have the same molecular formula, just a different structure isomers –these structural differences can effect some properties of the isomers --more carbons we add, the more isomers we could have 3. Rings – (see figure 5 on 265)

Note Guide 5-3 day 2 --Unsaturated Hydrocarbons: -sometimes hydrocarbons can contain multiple bonds (double, triple) = unsaturated hydrocarbons. -We classify unsaturated hydrocarbons by bond type and arrangement of the carbon atoms 3 Types: 1. Alkenes: have a double bond between the two carbon atoms. (draw ethene diagram pg 266 in notes) --fruit bearing plants produce ethene. --names in end -ene 2. Alkynes: hydrocarbons that have one or more triple bonds. (draw ethyne diagram pg. 266 in notes)

--most reactive hydrocarbon --names end in -yne 3. Aromatic: hydrocarbons which contain similar ring structures (draw benzene ring from 266 in notes) --many of these compounds have strong odor Most common hydrocarbon in our everyday life? Fossil fuels! Fossil fuels are mixtures of hydrocarbons formed from plant and animal remains. 3 types of fossil fuels: 1. Coal: mostly aromatic hydrocarbons. High ratio of carbon to hydrogen, causing more soot when burned. 2. Natural Gas: made from marine remains. Main ingredient is methane—same stuff produced by cows as they digest grass. Also contains ethane.

3. Petroleum: crude oil, texas tea! Made from marine organisms --Complex hydrocarbons(long-branched alkanes and alkynes) --useful only if separated into simpler mixtures: gas & heating oil. --To use fossil fuels, we must combust (burn) them. The combustion of fossil fuel produces 2 primary products: 1. Carbon dioxide: if too much fossil fuel is burned, an increase in the amount of CO2 may increase temperature, amounts of rain and sea levels around the world. --too much burning also causes the acidity of rain to increase. --rain has some acidity, with a pH of about 5.6. --the burning increases sulfur dioxide and nitrogen oxides and when dissolved in water, produces sulfuric acid and nitric acid! --causes structural damage on metals and concrete

Note Guide 5-4 Organic Acids and Bases --Hydrogen atoms can be replaced in a reaction by an atom or by a group of atoms = substituted hyrdrocarbon --the atom or group of atoms that does the substitution is called the functional group. --functional group determines the properties of the compound --Organic Acids: --citric acid is an example of an organic acid (sour taste in lemons) --the functional group is a carboxyl group (-COO) --Organic Bases: --amime is an example of an organic base (smell of rotten fish) --functional group is amino group )-NH2

Monomers and Polymers, Oh MY! --sometimes molecules can be built up from smaller units which are linked together: -Polymer: large molecule that forms when many smaller molecules are linked together by COVALENT BONDS! --the smaller units are called monomers --sometimes polymers are made up of just one monomer or they can be made up of more than one monomer --can be natural (cotton and wool) or synthetic (man made) --synthetic examples: nylon, rubber, polythylene (plastics)

Note Guide 5-1 – Acids and Bases