2- The Basics of Life: Chemistry Chapter 2. 2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levels of.

2- The Basics of Life: Chemistry Chapter 2

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levels of Organization of Life Cellular Organization cells organellesmolecules atoms The cell is the basic unit of life.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Life Requires Matter and Energy Matter is anything that has mass and occupies space. – Matter is composed of atoms Energy is the ability to do work. – Energy organizes atoms to form higher levels of organization

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Life Requires Energy Energy is the ability to do work. There are two types of energy: 1. Potential energy Stored energy, available to do work 2. Kinetic energy Energy of motion Potential energy can be converted to kinetic energy to do work.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Law of Conservation of Energy Energy is never created or destroyed. – The first law of thermodynamics Energy can only be converted from one form to another: – An object at the top of a hill has potential energy, as the object rolls down the hill, the potential energy is converted to kinetic energy. – Cells convert chemical energy into energy used for life processes The sum total energy remains constant.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Forms of Energy There are five forms of energy: 1. Mechanical energy Energy of movement 2. Nuclear energy Energy from reactions involving atomic nuclei 3. Electrical energy Flow of charged particles 4. Radiant energy Energy in heat, light, x-rays and microwaves 5. Chemical energy Energy in chemical bonds

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Life Requires Matter Matter is anything that has mass and occupies space. Matter is composed of atoms. Atoms – The smallest units of matter that can exist separately

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atoms Atoms are composed of: – Protons – positively charged particles – Neutrons – neutral particles – Electrons – negatively charged particles Protons and neutrons are located in the center of the atom (atomic nucleus) Electrons are found in orbits surrounding the nucleus (electron orbitals)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Elements Elements are chemical substances composed of the same kind of atoms – i.e. atoms with the same numbers of protons and electrons The elements are listed and organized on the periodic table – each element is represented by a symbol of one or two letters. The principal elements that comprise living things are: C, H, O, P, K, I, N, S, Ca, Fe, and Mg.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure Atoms are composed of: A. The atomic nucleus Protons - positively charged particles Neutrons – particles with no charge (neutral charge) B. Electrons Negatively charged particles Orbit the nucleus in energy levels The more energy an electron has, the larger its orbit Are constantly in motion

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Atomic Number Atoms of every element have a characteristic number of protons in the nucleus. Atoms with the same atomic number have the same chemical properties and belong to the same element. Atomic Number = number of protons in the nucleus of an atom

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Atomic Mass Number Mass Number = The sum of protons and neutrons is the atom’s atomic mass. Each proton and neutron has a mass of approximately 1 AMU (atomic mass unit). Electrons are very small in comparison to protons and neutrons – mass of an electron is approx. 1/1,800 of an AMU – electrons are negligible to the atomic mass

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Isotopes Must all atoms of the same element have the same atomic number? Must all atoms of the same element have the same atomic mass?

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Isotopes Isotopes – Atoms of the same element that have different numbers of neutrons. – The atomic weight on the periodic table is  the weighted average mass of all of the isotopes of an element.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Atomic Charge Atoms of the same element have equal numbers of electrons and protons. Stable atoms have an overall neutral charge. – Atoms that gain or loose protons will become charged atom – Atoms that gain or loose electrons will become a charged atom Charged atoms are known as ions

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ions Neutral atoms have the same number of protons and electrons Ions are charged atoms – Cations – have more protons than electrons and are positively charged (+) – Anions – have more electrons than protons and are negatively charged (-)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ions Oxidation - when an atom looses an electron (e - ) – forms cations Reduction - when an atom gains an electron (e - ) – forms anions

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Electrons Electrons occupy specific areas around the nucleus called orbitals. Electrons constantly move around the nucleus within the orbital Orbitals are areas around the nucleus where an electron is most likely to be found

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic Structure: Electron Levels Electrons occupy specific energy levels around the nucleus. – Electrons closest to the nucleus have the lowest energy. – Electrons further from the nucleus have higher energy. Energy levels hold specific numbers of electrons. – The first energy level can have up to 2 electrons. – All other energy levels can have up to 8 electrons.

Fig. 2.5 Electrons release energy as they fall from a high energy level to a lower energy level Electrons climb from a lower energy level to a higher energy level as they absorb energy

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Valence Electrons The electrons in the outermost energy level of an atom are known as valence electrons Atoms seek to have a full outer energy level. – Atoms that have full outer energy levels are stable. Octet Rule: Atoms prefer to have 8 valence electrons: Atoms will gain, loose, steal, or share electrons to fulfill the octet rule

32 Valence Electrons H has 1 e - Na has 1 Valence e - Ca has 2 Valence e - s C has 4 Valence e - s O has 6 Valence e - s

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Valence Electrons Become Familiar with the Valence Electron Configuration for the Elements: – Hydrogen (H): 1 – Carbon (C): 4 – Oxygen (O): 6 – Nitrogen (N): 5 – Chlorine (Cl): 7 – Sodium (Na): 1

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Formation of Molecules Atoms will gain, loose, steal, or share electrons to fulfill the octet rule Atoms can fulfill the octet rule by loosing, gaining or sharing electrons with other atoms This creates chemical bonds between atoms

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Formation of Molecules Molecules consist of two or more atoms joined by a chemical bond. O 2, H 2 O A compound is a chemical substance made of two or more different elements combined in chemical bonds. – The formula of a compound describes the nature and proportions of the elements that comprise the compound. H 2 O

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Molecules and Kinetic Energy Molecules are constantly in motion. Temperature is a measure of the average speed of the molecules in a substance. – The greater the speed, the higher the temperature. – Measured in Fahrenheit or Celsius Heat is a measure of the total kinetic energy of molecules. – Measured in calories (amount of heat that will raise 1g of water 1 degree Celsius). Heat and Temperature are related. – Add heat energy to a substance and the molecules will speed up, and the temperature will rise.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Physical Changes and Phases of Matter Three phases of matter – Solid – Liquid – Gas The phase in which a substance exists depends on its kinetic energy and the strength of its attractive forces. – Solids−strong attractive forces, low kinetic energy, little to no molecular movement. – Liquid−enough kinetic energy to overcome the attractive forces; more molecular movement. – Gas−high kinetic energy, little to no attractive forces; maximum movement.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Changes—Forming New Kinds of Matter Chemical reactions – Creating different chemical substances by forming and breaking chemical bonds. There are several types of chemical bonds. Ionic bonds Covalent bonds Hydrogen Bonds

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ionic Bonds An ionic bond – The attraction between oppositely charged ions Example: NaCl – Sodium (Na) has one electron in its outer energy level. – Chloride has seven electrons in its outer energy level. – Sodium donates an electron to chloride, each achieving stability. – The positively charged sodium is attracted to the negatively charged chloride.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ionic Bonds Na easily gives up its single valence electron to fulfill the octet rule Because Na lost an electron it now has a positive (+) charge

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ionic Bonds Cl, with 7 valence electrons, easily picks up the extra electron to fulfill the octet rule Because Cl gained an electron it now has a negative (-) charge

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Covalent Bonds Covalent bonds form when atoms share 2 or more valence electrons Covalent bond strength and length depends on the number of electron pairs shared by the atoms Single Covalent Bond - one pair of e-’s is shared Double Covalent Bond - two pairs of e-’s are shared Triple Covalent Bond - three pairs of e-’s are shared Covalent Bonds are the strongest bonds and do not dissociate in water

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Bonds: Electronegativity Electronegativity is an atom’s affinity for electrons - how badly an atom wants e - ’s Atoms of each of the elements differ in electronegativity – Atomic size, mass, nuclear charge, electron configuration attribute to differences in electronegativity Based on what you know about the Na atom, do you think Na has a high or low electronegativity? What about Cl?

50 Chemical Bonds: Electronegativity

51 Lowest EN Greatest EN Increasing EN Electronegativity(EN) Trend in the Periodic Table

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Covalent Bonds: Polar Covalent Bonds A covalent bond is formed by a sharing of electrons, but electrons are not always shared equally Differences in electronegativity dictate how electrons are actually distributed in covalent bonds In a covalent bond between a highly electronegative atom and a weakly electronegative atom, electrons will be pulled more towards the highly electronegative side of the bond

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Covalent Bonds: Polar Covalent Bonds The water molecule is an important example of a covalent bond between a highly electronegative atom and a weakly electronegative atom As a result of this unequal sharing of electrons, one side of the molecule (the highly electronegative oxygen side) has a partial negative charge and the other side (the hydrogen side) has a partial positive charge

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Covalent Bonds: Polar Covalent Bonds A covalent bond with an unequal sharing of electrons is known as a polar covalent bond Polar because it has two ‘poles’, a partial positive pole and a partial negative pole A covalent bond with an equal sharing of electrons is known as a nonpolar covalent bond A Carbon to Carbon covalent bond is an example of a nonpolar covalent bond C C

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hydrogen Bonds The positive hydrogen end of one polar molecule is attracted to the negative end of another polar molecule. – This attraction is a hydrogen bond. Hydrogen bonds hold molecules together. – Since they do not hold atoms together, they are not considered true chemical bonds. Hydrogen bonds are very important in biology. – They stabilize the structure of DNA and proteins. – Water molecules can “stick” together with hydrogen bonds.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Water and Life The following properties of water make it essential for life: – High surface tension Water molecules stick to each other via hydrogen bonds. Capillary action moves water through streams, soil, animals and plants. – High heat of vaporization A lot of heat is required to break the hydrogen bonds holding water together. Large bodies of water absorb a lot of heat. – Temperate climates – Evaporative cooling

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Water and Life Unusual density properties – Ice is less dense than water, so ice floats. – Allows aquatic life to survive in cold climates. The universal solvent – Water can form hydrogen bonds with any polar or ionic compound. – Therefore, many things can be dissolved in water.

2- Introduction to Life Science Chapter 1 Begin 1/20/2011

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mixtures and Solutions Mixture – Matter that contains two or more substances Homogeneous mixture – Components are distributed equally throughout. Heterogeneous mixture – Components are not distributed equally throughout.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mixtures and Solutions Solutions – Homogeneous mixture of ions or molecules of two or more substances. – The solvent is the substance present in the largest amount. – The solutes are the substances present in smaller amounts. Aqueous solutions – water is the solvent – solid, liquid or gas solutes dissolved in water.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Concentration of Solutions Molarity (M) is the unit for concentration M= Amount of solute Liters of solution Amount of solute measured in moles  1 mole = 6.022x10 23 particles (atoms, molecules) of substance Atomic mass on the periodic table is measured in grams/mole (g/mol)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Reactions A chemical change: – Bonds between atoms are made or broken to make new materials with new properties – Happens via chemical reactions. In a chemical reaction the elements remain the same, but the compounds they form and their properties are different.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Five Important Chemical Reactions in Biology 1. Oxidation–Reduction (Redox Reactions) 2. Dehydration Synthesis Reactions 3. Hydrolysis Reactions 4. Phosphorylation Reactions 5. Acid–base Reactions

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Reactions and Energy Chemical reactions produce new compounds with less or more potential energy. – Catabolic Reactions Breakdown large molecules into smaller ones Release energy – Anabolic Reactions Build larger molecules from smaller ones Require energy

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Equations A chemical equation describes what happens in a chemical reaction. – Photosynthesis is described by the following equation: – 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6H 2 O Reactants−substances that are changed, usually on the left side of the equation. Products−new chemical substances formed, usually on the right side of the equation. Chemical equations must be balanced – They must have the same number of atoms of each element on both sides of the equation

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Five Important Chemical Reactions in Biology 1. Oxidation–reduction 2. Dehydration synthesis 3. Hydrolysis 4. Phosphorylation 5. Acid–base reactions

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation-Reduction Reactions Reactions in which electrons (and their energy) are transferred from one atom to another. – Oxidation - an atom loses an electron. – Reduction - an atom gains an electron. Redox Reactions are very important in biological processes  Cellular Respiration, Photosynthesis

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation-Reduction Reactions LEO the lion says GER – If it Looses Electrons, it’s Oxidized – If it Gains Electrons, it’s Reduced

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation-Reduction Reactions Oxidation and Reduction reactions always occur in pairs: – If a an atom or molecule is reduced, then another atom or molecule must have been oxidized – If a an atom or molecule is oxidizied, then another atom or molecule must have been reduced For this reason Oxidation and Reduction Reactions are known as Redox Reactions

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation-Reduction Reactions In Biology, hydrogen atoms are commonly transferred during redox reactions. Cellular Respiration - The sugar glucose is oxidized to form carbon dioxide and oxygen is reduced to form water. - Energy is released in the process. – C 6 H 12 O 6 + 6O 2 → 6H 2 O + 6CO 2 + Energy Sugar + oxygen → water+ carbon dioxide + energy – (glucose)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis Reaction Biological molecules are typically Marcomolecules – very large molecules with high molecular weights – DNA over a meter long Macromolecules are Polymers assembled from smaller Monomers – Monomers - small, identical or similar subunits – Polymers - covalently bonded monomers

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis Reaction Proteins – Amino Acid monomers polymerize to form proteins Nucleotides – Nucleotide monomers polymerize to form DNA and RNA Macromolecules Carbohydrates – Simple sugar monomers polymerize to form complex sugars Monosaccharides polymerize to form disaccharides, polysaccharides

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis Reaction Two small molecules are joined to form a larger molecule Example: – Joining amino acids to form proteins. – NH 2 CH 2 CO-OH + H-NH CH 2 CO-OH  NH 2 CH 2 CO-NH CH 2 CO-OH + H- OH amino acid 1 + amino acid 2 = protein + water

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis Reaction Dehydration Synthesis - the chemical reaction for how living cells synthesize macromolecules A covalent bond is formed between monomers and water is produced as a product of the reaction As the name implies, water is lost during the reaction - dehydration

2-67 Dehydration Synthesis Reaction Monomers covalently bond together to form a polymer with the removal of a water molecule –A hydroxyl group is removed from one monomer and a hydrogen from the next Monomer 1Monomer 2 OH HO OH – + O Dimer (a) Dehydration synthesis H+H+ H2OH2O Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 2.15a

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis Reaction A hydroxyl (-OH) group is removed from one monomer, and a hydrogen (H+) from another A new covalent bond is formed between the monomers - OH and H + come together to form water (H 2 O) – Water is released as a by-product

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hydrolysis Reactions When a larger molecule is broken down into is smaller smaller subunits Opposite of a dehydration synthesis Example: – Digesting proteins into amino acids. – NH 2 CH 2 CO-NH CH 2 CO-OH + H-OH  NH 2 CH 2 CO-OH + H-NH CH 2 CO-OH – Protein + water = amino acid 1 + amino acid 2

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hydrolysis Reactions The reaction for the separation of joined monomers “Splitting with water” Opposite of dehydration synthesis – a water molecule ionizes into – OH and H + – the covalent bond linking one monomer to the other is broken – the – OH is added to one monomer – the H + is added to the other

2-68 Hydrolysis Reactions Splitting a polymer (lysis) by the addition of a water molecule (hydro) –a covalent bond is broken All digestion reactions consists of hydrolysis reactions OHHO Monomer 1Monomer 2 O Dimer (b) Hydrolysis OH – +H+H+ H2OH2O Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 2.15b

85 Biological Molecules

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phosphorylation Reactions The addition of phosphate groups to other molecules, – Phosphate groups (P) are clusters of oxygen and phosphate atoms. Functions of Phosphorylation: – Phosphorylation is used to turn enzymes on or off – Phosphorylation is used to transfer energy –

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phosphorylation Reactions Bonds between phosphate groups and other molecules contain high potential energy. – When these bonds are broken, the energy that is released can be used by the cell to do work. – Phosphorylation reactions are commonly used to transfer potential energy. – Q-P + Z  Q + Z-P

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids and Bases An acid – Ionic compounds that release hydrogen ions (H + ) into a solution – Phosphoric acid, hydrochloric acid A base – Compounds that release hydroxide ions (OH-) into a solution or accept hydrogen ions (H + ) from solution – Sodium hydroxide, ammonia Acids and Bases react to neutralize each other producing water and salts – The - OH from bases are negatively charged, they will react with a positively charged H + from an acid to produce water.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids and Bases Acid: a chemical that releases H + ions - Hydrochloric acid, HCl HCl  H + + Cl - - Sulfuric acid, H 2 SO 4 H 2 SO 4  2H + + SO 4 -2 - Carbonic acid, H 2 CO 3 H 2 CO 3  H + + HCO 3 -

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids and Bases Base: a chemical that releases - OH ions or accepts H +1 ions Sodium Hydroxide, NaOH NaOH  Na +1 + OH -1 OH -1 + H +1  H 2 O Bicarbonate, HCO 3 - HCO 3 - + H +  H 2 CO 3  carbonic acid

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acid-Base Reactions Occurs when ions from an acid interact with ions from a base. This type of reaction allows harmful acids and bases to neutralize one another. HCl + NaOH → NaCl + HOH H + Cl - + Na + OH - → Na + Cl - + H + OH - Hydrocloric + Sodium Sodium + Water acid hydroxide chloride

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Salts Usually formed when acids and bases react – The dissociated hydrogen ions and hydroxide ions join to form water. – The remaining ions form ionic bonds, creating a salt. – This is an example of neutralization: H + Cl - + Na + OH - → Na + Cl - + H + OH - Hydrocloric + Sodium Sodium + Water acid hydroxide chloride

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acid-Base Reactions Acids and Bases come in pairs: H 2 CO 3  H +1 + HCO 3 - Carbonic acid Bicarbonate HCO 3 - + H +  H 2 CO 3  Bicarbonate Carbonic acid H 2 CO 3  H +1 + HCO 3 -

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids and Bases The strength of an acid or base is determined by how completely it will dissociate in water. Strong acids release almost all of their hydrogen ions into water. Strong bases release almost all of their hydroxide ions into water.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acids and Bases The acidity/basicity of a solution is measured in terms of the pH Scale pH is a measure of hydrogen ion concentration [H + ] in a solution Solutions with high hydrogen ion concentrations are acidic Solutions with low hydrogen ion concentrations are basic (alkaline)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The pH Scale Hydrogen ion concentration [H +1 ] is the basis of the pH scale: pH = -log [H + ] or pH = 1 log [H + ] Greater H +1 concentration = lower pH (acidic) Lower H +1 concentration = higher pH (basic)

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pH The pH Scale makes large numbers easier to use Log Function: – The Log of 10000000 = 7 – The Log of 0.0000001 = -7 There is a 10-fold difference in hydrogen ion concentration between solutions that differ by one pH unit. – A solution with pH 4 has ten times as many hydrogen ions as a solution with pH 5.

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The pH Scale Hydrogen ion concentration [H +1 ] of pure water is 10 -7 moles [H + ] / L pH = 1 pH water = 1 log [H + ] log [10 -7 ] pH water = 7 The pH scale is based on the pH of pure water

2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The pH Scale Is water an acid or a base? H 2 O  OH - + H + H 2 O + H +  H 3 O + Water acts as an acid and a base Pure water exists as a balance of H 2 O, OH -1, and H 3 O +1 Water has a neutral pH

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2- The Basics of Life: Chemistry Chapter 2. 2- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levels of.

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