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Other Classification of Reactions. Water as a Solvent. _______________ – substance being dissolved _______________ – substance doing the dissolving Water is the universal solvent – _______________ _______________. Water as a Solvent.
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Water as a Solvent • _______________ – substance being dissolved • _______________ – substance doing the dissolving • Water is the universal solvent – _______________ _______________
Water as a Solvent • Some solvents play a _______________ role – disperse dissolved substances into individual molecules but doing nothing else. • Water plays an _______________ role – interacts strongly with substances and in some cases, reacting with other substances.
Water as a Solvent • 2 major factors that contribute to water’s ability to act as a solvent: • The distribution of the bonding _______________ • Overall _______________
Water as a Solvent • Water is _______________ bonded – shared electrons between nonmetals and nonmetals. • Even in the sharing of electrons, one element can have more of an _______________ for the electrons than another element. • Atoms of the same element that are covalently bonded share equally.
Water as a Solvent • Oxygen has a _______________ attraction for the electrons than hydrogen. • In water, the electrons spend more time closer to the oxygen atom than the hydrogen atom.
Water as a Solvent • When a molecule has unequal sharing of electrons, we call it a _______________ molecule. • When a molecule has equal sharing of electrons, we call it a _______________ molecule. • When there is a complete electron transfer, as in ionic bonding, it is called an ionic bond or _______________ compound.
Water as a Solvent • Water has unequal sharing of electrons, therefore, it is a _______________ _______________.
Water as a Solvent • With an ionic solid in water, the oppositely charged ions are held next to each other by _______________ attraction. • Water separates the ions by replacing that attraction with one between the water molecules and the ions.
Water as a Solvent • The negative ends of the water molecules are attracted to the positive _______________, and the positive ends of the water molecules are attracted to the negative _______________. • The attraction becomes great enough that the ions separate (_______________) and become _______________ (surrounded by solvent molecules).
Water as a Solvent • When an ionic compound dissolves, an important change occurs in the solution. • The solution becomes electrically conductive.
Water as a Solvent • A substance that conducts a current when dissolved in water is an _______________. • Soluble ionic compounds are _______________ electrolytes because they dissociate completely.
Water as a Solvent • Some compounds only dissociate partially and are called _______________ electrolytes. • Some compounds do not dissociate at all and are called _______________ • Covalently bonded compounds are _______________ – no ions ever form
Solubility Rules • Those substances that are soluble and form ions completely: • All ammonium (NH4+) compounds, all Alkali metals, all nitrates (NO3-), all chlorates (ClO3-), all acetates (C2H3O2- - with the exception of acetic acid)
Solubility Rules • All chlorides (Cl-), bromides (Br-), and iodides (-) with the exception of Hg2+, Ag+, and Pb2+ • All sulfates (SO42-) with the exception of Sr2+, Ba2+, Hg2+, Pb2+ • Strong Acids – HCl, HNO3, HClO3, HClO4, H2SO4, HBr, H
Solubility Rules • Those that are not soluble: • All hydroxides (OH-) except calcium (Ca2+), barium (Ba2+), and strontium (Sr2+) • All phosphates (PO43-), carbonates (CO32-), chromates (CrO42-), oxalates (C2O42-), sulfides (S2-), fluorides (F-), and oxides (O2-) • All molecules (nonmetal-nonmetal compounds), solids, liquids, and gases.
Using the Solubility Rules • _______________ Equations – reveals the least about the species in solution and shows all the reactants and products in the equation. • _______________ Equations – shows all the soluble and insoluble substances with spectator ions eliminated.
Using the Solubility Rules • _______________– those that are in the equation but remain unchanged and are not involved in the actual chemical change.
Writing Net Ionic Equations • 1. Write the molecular equation first. • 2. Dissociate all substances that are soluble. • 3. Cancel out any spectator ions. • 4. Rewrite the final net ionic equation (NIE)
Precipitation Reactions • Two soluble ionic compounds react to form an insoluble product – _______________.
Pb(NO3)2 + Na NaNO3 + Pb2 • Pb(NO3)2 and Na are soluble and will form ions of Pb2+, NO3-, Na+ and - • NaNO3 is soluble and will form ions of Na+ and NO3- • Pb2 is not soluble and will not form ions • Pb2+ + NO3- + Na+ + - Na+ + NO3- + Pb2 • Cancel out the spectator ions – Na+ and the NO3- • Pb2+ + - Pb2 is the final net ionic equation
This solid formed in this reaction is the Pb2, as can be seen from the precipitation reaction and the net ionic equation written.