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Chemistry and Life The Periodic Table Atomic Number: Number of Protons and Electrons Atomic mass: Mass relative to Carbon-12 Chemical Bonding HUGE: ONLY THE ELECTRONS ARE INVOLVED IN MAKING CHEMICAL BONDS!!! More specifically, the only the one’s on the outermost “shell” Covalent Bond Covalent bonds are generally when two or more atoms share one or more pairs of electrons. Nonpolar Covalent Bond when these shared pairs of electrons are shared EQUALLY! Polar Covalent Bond when these shared pairs of electrons are NOT shared equally! Common Polar Covalent Bond??? Ionic Bond bond formed between oppositely charged ions. This happens when the stronger atom steals 1+ electrons from the weaker atom. They both have their outer shells filled, so all is good. Ions Cl- is such a beast that it pulls the outer electron from Na. Now both are happy. They are both now ions. Chlorine Sodium Hydrogen Bonds These are weak bonds that are caused by the weak positive charge of the hydrogen atom to other negative atoms. Solutes and Solvents Which is the solute and which is the solvent? Solutes and Solvents Solute: The stuff the gets dissolved Solvent: The stuff that does the dissolving The Mole: A Measurement of Matter OBJECTIVES: Distinguish between the atomic mass of an element and its molar mass. How do we measure items? You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES. What is the mole? We’re not talking about this kind of mole! Moles (is abbreviated: mol) It is an amount, defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mole = 6.02 x 23 10 of the representative particles. Treat it like a very large dozen 6.02 x 1023 is called: Avogadro’s number. Similar Words for an amount Pair: 1 pair of shoelaces = 2 shoelaces Dozen: 1 dozen oranges = 12 oranges Gross: 1 gross of pencils = 144 pencils Ream: 1 ream of paper = 500 sheets of paper Examples Calculate the molar mass of the following and tell what type it is: = 78 g/mol gram formula mass Na2S = 92 g/mol gram molecular mass N2O4 C = 12 g/mol gram atomic mass Ca(NO3)2 = 164 g/mol gram formula mass C6H12O6 = 180 g/mol gram molecular mass (NH4)3PO4 = 149 g/mol gram formula mass For example How many moles is 5.69 g of NaOH? 5.69 g For example How many moles is 5.69 g of NaOH? mole 5.69 g g We need to change 5.69 grams NaOH to moles For example How many moles is 5.69 g of NaOH? mole 5.69 g g We need to change 5.69 grams NaOH to moles 1mole Na = 23 g 1 mol O = 16 g 1 mole of H = 1 g For example How many moles is 5.69 g of NaOH? mole 5.69 g g We need to change 5.69 grams NaOH to moles 1mole Na = 23 g 1 mol O = 16 g 1 mole of H = 1 g 1 mole NaOH = 40 g For example How many moles is 5.69 g of NaOH? 1 mole 5.69 g 40.00 g We need to change 5.69 grams NaOH to moles 1mole Na = 23 g 1 mol O = 16 g 1 mole of H = 1 g 1 mole NaOH = 40 g For example How many moles is 5.69 g of NaOH? 5.69 g 1 mole = 0.142 mol NaOH 40.00 g We need to change 5.69 grams NaOH to moles 1mole Na = 23 g 1 mol O = 16 g 1 mole of H = 1 g 1 mole NaOH = 40 g Chemical Reactions An Overview How do you know a reaction has taken place? A new substance is formed Heat is produced or absorbed A gas is released How to write a reaction Example: Hydrogen gas + Oxygen gas = Water Here ya go! H2 + Reactants H2 and O2 O2 H 2O Products H 2O Types of Reactions Synthesis: 2 or more substances combine to make a new one. Example: H2 + O2 H 2O Decomposition: 1 substance is broken into 2 or more substances H2O H2 + O2 Single Displacement: One element replaces another element. Cu + AgNO3 CuNO3 + Ag The Silver replaced the Copper Demo Double Displacement: Two elements switch places. Two Ions are mixed together and a precipitate is formed A precipitate is an insoluble compound formed during the reaction PbNO3 + KI PbI2 + KNO3 OXIDATION/ REDUCTION STUFF OXIDATION: LOSS OF ELECTRONS EXAMPLE: SODIUM IN THE PRESENCE OF CHLORINE REDUCTION: GAIN OF ELECTRONS EXAMPLE: CHLORINE IN THE PRESENCE OF SODIUM ***THE TWO REACTIONS ALWAYS OCCUR TOGETHER!! What the heck is pH? ACID: PROTON DONOR (BASICALLY, A DONATION OF H+ IONS. WHAT IS H+ REALLY? BASE: PROTON ACCEPTOR; RELEASES – OH IONS More on pH… IT IS SIMPLE THE LOG OF THE INVERSE OF THE HYDROGEN ION CONCENTRATION. (NOW, IN ENGLISH): THE LOWER THE pH, THE HIGHER THE [H+], THE HIGHER THE pH, THE LOWER THE [H+]. EACH SCALE NUMBER OF pH REPRESENTS A TENFOLD INCREASE OR DECREASE IN THE [H+]. Answer: 100x (10x10) EXAMPLE: HOW MUCH MORE ACIDIC IS pH=2 AS COMPARED TO pH=4? Answer= 10 x 10 = 100 BUFFERS BUFFERS: THEY RESIST A CHANGE IN pH OF A SUBSTANCE BY EITHER ACCEPTING OR DONATING H+ IONS IN THE PRESENCE OF AN ACID OR A BASE