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Lecture 21

CHEM 130 Lecture Notes - Lecture 21: Chemical Polarity, Lattice Energy, Acid Strength

Course Code
CHEM 130
Charles Mc Mory

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Thursday, March 14, 2019
CHAPTER 6: Types of chemical reactions and solutions
(6.1) Water
Water is a polar molecule.
Interactions between polar water molecules and the inns o a interaction btwn polar molecules
and the ions of a salt leads to hydration
If a salt is put in water it breaks apart and positive parts of dipole are attracted to the
negative ions in the salt and the negative dipole is attracted to the positive ions in the salt
These strong attractions overcome the lattice energy —> why they dissolve in water
ex. NaCL (s) H20>Na+ (aq) + Cl- (aq)
solubility: “how well something dissolves”
* the attraction of ins to water molecules is greater than the attraction of ions to each other *
(6.2) The nature of aqueous solutions: strong and weak electrolytes
electrolytes: substance that dissolves to produce ions
The ions, as moving charges, complete a circuit (conduct electricity)
Some molecules resolve in water but produce on ions
ex. non-electrolytes—> sucrose
Conductivity of a solution depends on the number of ions present
Strong electrolytes readily produce ions in aqueous solutions
soluble salts, strong acids, strong bases
Ex: hydrochloric acid—> H+ C- fully disassociate
Weak electrolytes: produce a smaller percent of ions in an aqueous solution
does not produce all ions but still soluble, mostly molecules in solution
Weak acid or base
Non electrolytes: do not produce inns in solution when dissolve
Covalent (organic molecules) —> sucrose
(6.3) The composition of solutions
Molarity: molar concentration (molarity)
Number of moles of solute per column of solution in L
unit= mol/L
M= molarity= moles of solute
liters of solute
CLICKER: A 4.00 g sugar cube (sucrose: C12H22O11) is placed in a 350. mL volumetric flask (or a
mug) that is then filled to the mark with hot water. What is the molarity of the solution?
a) 3.344 x 10-5 M
b) 1.17 x 10-5 M
c) 3.344 x 10-2 M
d) 1.17 x 10-2 M
e) 11.4 M
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