Types of Chemical Reactions SOLUTION STOICHIOMETRY

Water, the Common Solvent  V-shaped (sometimes called bent)  H-O-H bond angle is 105°  Covalent bonding, but the electrons of the bond are not shared equally and the bond is said to have a dipole (charge separation).  WHY? Oxygen is much more electronegative atom than hydrogen: the shared electrons are attracted to oxygen more than hydrogen.

POLARITY  An unequal sharing of electrons in a bond causes there to be a charge separation and though not like in an ionic bond where the electron is transferred, the atom with more electron ‘pull’ will have a partial negative charge because it experiences more electrons than in the neutral atom. Likewise the opposing atom will have a partial positive charge because it feels less electron density than its neutral state.  If the individual bond DIPOLES (charge separations) CANCEL in a covalent molecule, then the molecule is NONPOLAR. Methane  If the individual bond dipoles do NOT cancel each other out then the molecule is POLAR. Water

WATER is POLAR  POLAR = NET DIPOLE  NONPOLAR = NO NET DIPOLE Individual bond dipoles CANCEL

Intermolecular forces of attraction (between molecules) are very strong and explain its high boiling point, 100°C. These IMF’s in water are called hydrogen bonds, but do not confuse these attractions with chemical bonds!

Water’s polarity explains its ability to DISSOLVEmany compounds.

Electrolytes- any species that allows movement of charge (ions)=> conducts electricity  Strong electrolytes- 100% ionize when dissolved in water  STRONG ACIDSSTRONG BASES SOLUBLE SALTS HClLiOHKnow your Rules HBrNaOH HIKOH HClO4CsOH HNO3 H2SO4  Weak electrolytes – ionize only to a small degree when dissolved in water. (organic acids)  Nonelectrolytes – molecular(covalent) compounds when dissolved in water do not ionize. (sugar)

Remember Solubility Rules from summer camp! Quiz tomorrow  All group I metal salts and ammonium salts are soluble Li +, Na +, K +, Rb +, Cs + and NH 4 +  All nitrates are soluble, NO 3 - and acetates are soluble, C 2 H 3 O 2 -  Most chlorides, bromides, and iodides are soluble EXCEPT Ag+, Pb(2+), Hg 2 (2+)  Most sulfates are soluble EXCEPT Ag+, Pb(2+), Hg 2 (2+), Ca (2+), Sr (2+), Ba (2+)

MEMORIZE YOUR POLYATOMICS!!!! Daily quizzes until you score 100%  For those of you that do not listen: You are losing needless points on tests due to your lack of initialtive- FIX IT! FIX IT! FIX IT!

Precipitation Reactions (DR)  When two aqueous solutions are mixed and a solid forms. CAUTION ABOUT THE CONTEXT: solids formed from mixing solutions are called precipitates.  These rxns are double replacement (DR) type- meaning ‘switch partners’ to determine the products.

Q: Write the reaction when aqueous potassium carbonate is added to lead(II) nitrate.  Step 1 : write the formulas for each of the solutions being mixed. K2CO3 + Pb(NO3) > PRODUCTS  Step 2 : switch partners to get products: cation of first solution goes with the anion of the second solution. My analogy to help you remember this is from multiplying binomials: outer ions pair up, inner pairs up K2CO3 + Pb(NO3)2  Step 3: Do NOT carry subscripts into products. You MUST rebalance charges to get the proper product formulas. KNO 3 + PbCO 3

POP QUIZ  Mixing of which of the following solutions will cause a precipitate to form? (a) Potassium nitrate and barium chloride (b) Sodium sulfate and lead(II) nitrate (c) Potassium hydroxide and iron(III) nitrate

A precipitation reaction occurs when mixing solutions a precipitate forms.  ____________ _____________ are used to determine if a precipitate froms.  Draw what is in the beaker containing a silver nitrate solution.  Draw what is in the beaker containing an ammonium chloride solution.  A student pours the contents of the first beaker into the second. Draw the result of this mixing.

On the AP assume ALL RXNS OCCUR  When solutions are mixed and no precipitate forms then nothing new is made = No RXN  Draw what is in the beaker containing a solution of sodium chloride.  Draw what is in the beaker containing a solution of zinc sulfate.  A student pours the first beaker’s contents into the second. Did a reaction occur? Draw the beaker’s contents to Justify your answer.

Molarity – the concentration of a solution expressed in moles of solute per litre of solution.

Molarity: A new way to get moles  List all of the ways to get moles of a substance that you have learned thus far.

Molarity: used as a conversion ratio

Writing Chemical Equations  Notes page 8 BALANCE IT! Balance atoms AND charge when applicable (a)

Writing Chemical Rxns cont’d  (b)

Work all the problems in the notes, up to acid-base reactions pg 11  Topics covered thus far: Properties of water, dissolving solutes, strong vs weak electrolytes and nonelectrolytes, solution concentration, preparing solutions to a known concentration, dilutions, solubility rules, precipitation reactions, writing equations in different forms.