Unit 11 Solutions

Solution – homogeneous mixture containing two or more substances. ______________ – substance being dissolve ______________ – substance doing the dissolving

Solution may exist as a gas, liquid or solid: Air – solution of gases Braces – a solid solution of titanium in nickel Hydrochloric acid – liquid solution of pure HCl mixed in water.

______________ – a substance that dissolves in a solvent ______________ – a substance that does not dissolve in a solvent. ______________ – two liquids that will dissolve in each other. ______________ – two liquids that do not dissolve in each other.

Like Dissolves Like Substances that are alike in structure and bonding will dissolve in each other.

Polarity ______________ bonding – sharing of electrons Atoms do not always share electrons equally. Some atoms have a greater attraction for electrons than other atoms – ______________. Fluorine is the highest Francium is the lowest

Polarity In covalent bonding, when the electrons are shared equally, the bond is ______________. In covalent bonding, when the electrons are not shared equally, the bond is ______________. When there is a transfer of electrons, the bond is ______________.

Nonpolar Covalent Bonds Those atoms that are bonded to themselves H2, N2, O2, F2, Cl2, Br2, I2

Polar Covalent Bonds Any molecule that has atoms bonded to something other than itself. CO NO2 P2O5

Molecular Structures Lewis structures help us identify what type of structure we are dealing with. This can help us identify if two substances are miscible or soluble.

Lewis Structures Lewis structures are representations of molecules showing all electrons, bonding and nonbonding. Lewis structures can help us identify if two substances are miscible or soluble.

Writing Lewis Structures Find the sum of valence electrons of all atoms in the polyatomic ion or molecule. If it is an anion, add one electron for each negative charge. If it is a cation, subtract one electron for each positive charge. PCl3 5 + 3(7) = 26

Writing Lewis Structures The central atom is the least electronegative element that isn’t hydrogen. Connect the outer atoms to it by single bonds. The “−” represents a shared pair of electrons. Keep track of the electrons: 26  6 = 20

Writing Lewis Structures Fill the octets of the outer atoms. The only atoms that do not have an octet are hydrogen, helium, and boron (exception to the rule). Keep track of the electrons: 26  6 = 20  18 = 2

Writing Lewis Structures Any extra electrons are drawn on the central atoms as pairs. If there are not enough electrons, double and triple bonds can be drawn. Keep track of the electrons: 26  6 = 20  18 = 2  2 = 0

Writing Lewis Structures If you run out of electrons before the central atom has an octet… …form multiple bonds until it does.

Polarity of Molecules Most molecules are ______________ – they have slightly positive ends and slightly negative ends. H2O is slightly negative on the oxygen end and slightly positive on the hydrogen end. Water is the universal solvent because of these slightly charged ends.

Polarity of Molecules Some molecules are ______________ even though they have polar bonds. These molecules cancel their polarity out. They tend to be ______________.

Like Dissolves Like Those molecules that are alike tend to be miscible or soluble in one another. Polar can dissolve ______________ and ______________. Nonpolar can only dissolve ______________.

Solubility There are other factors that can affect the solubility of solid substances in a ______________.

Solubility Temperature An increase in temperature can increase the solubility for most substances. ______________ solution – more solute than a saturated solution at the same temperature. ______________ solutions – more solute can be dissolved in a solvent. ______________solutions – the maximum amount of solute is dissolved in a given amount of solvent.

Solubility Temperature Temperature greatly affects the solubility of gases. Gases become more soluble in ______________ temperatures. Gases become less soluble in ______________ temperatures. Thermal pollution

Solubility Pressure Pressure affects the solubility of gases The ______________ the pressure, the more soluble gases become. The______________the pressure, the more insoluble gases become.

Solution Concentrations Molarity Most solutions have a concentration expressed in ______________, M. Molarity is found by dividing the moles of solute by liters of solution. M = moles of solute liters of solution or M = mol L

Preparing Molar Solutions Dilution M1V1 = M2V2 Stock solution (M1V1) New solution (M2V2)

Preparing Molar Solutions Solution from a solid Grams = (M) (amu) (volume in L) Where, M = molarity wanted L = volume of solution wanted in liters amu = molar mass of the compound