solutions, acids, and bases
DESCRIPTION
Solutions, Acids, and Bases. Chapter 7. Solute The substance that is dissolved into the solution. examples: Sugar in kool-aid Salt in salt water CO 2 in pop. Solvent The substance that does the dissolving in a solution. examples: Most common is water. Parts of a solution. - PowerPoint PPT PresentationTRANSCRIPT
Solutions, Acids, and Bases
Chapter 7
Parts of a solution
SoluteThe substance that is dissolved into the
solution.examples:
• Sugar in kool-aid• Salt in salt water• CO2 in pop
SolventThe substance that does the dissolving
in a solution.examples:
• Most common is water.
Dissolving
Three ways to dissolve a solute in a solvent:
1. Dissociation2. Dispersion3. Ionization
Conductivity
Many solutions can conduct an electric current if electrolytes are present. (ions)
Electrolytes = substances that will conduct an electric current when dissolved. Ex. NaCl, KCl, MgBr2
Freezing Point Depression
Lowering the freezing point of water by the addition of a solute
ex. salt. Used on icy roads in
winter Ice-cream
Boiling point elevation
The addition of a solute to a liquid solvent will usually raise the boiling point of the solvent.
Adding salt to boil water when cooking
Concentration
ConcentratedA large amount of solute dissolved
in a solvent
DiluteA little bit of solute dissolved in a
solvent
Saturation
A solution that contains all the solute it can possibly hold at a given temperature is said to be saturated.
Unsaturated = contains less solute than it can possibly hold
Supersaturated = a solution that holds more solute than it should at a given temperature.
Supersaturation example:
Sodium acetate in water.
Used in commercial hand warmers.
InsolubleA
substance that will NOT dissolve in water.
“Like dissolves like”
Nonpolar solvents will dissolve nonpolar solutes.
examples: benzene & acetone Polar solvents will dissolve polar solutes
2 factors that affect solubility:
1.Temperature Increase in temp generally increases
solubility of a solid in a liquid Increase in temp decreases solubility of
a gas in a liquid.
2. Pressure Usually has little, if any, effect on solid
and liquid solutes. Increase in pressure increases the
solubility of a gas in a liquid.
Specific concentration
Can be defined as percent by volume or percent by mass
Example: 3% hydrogen peroxide or 25% fruit juice.
Acids
Very important chemicals in everyday life processes.
Properties of acids:
1. Sour taste (never taste a chemical)2. All contain hydrogen3. Also called “proton donors”4. React with active metals to produce
hydrogen gas. Zn + 2HCl ZnCl2 + H2
Indicators
Chemicals used to identify acids and bases by changing color.
ACIDS:A. Litmus paper (blue to red)B. Phenolphthalein (colorless)C. Methyl Orange (orange to red)D. Bromothymol Blue (changes to yellow)
Common acids
Sulfuric (H2SO4) used in car batteries Nitric (HNO3) also fertilizers Hydrochloric (HCl) stomach acid Carbonic (H2CO3) carbonated drinks Acetic (HC2H3O2) vinegar
Bases
Also very important in everyday processes.
Properties of Bases:
Taste bitter; feel slippery Contain hydroxide (OH) ions. Known as “proton acceptors” Phenolphthalein turns bright pink Red litmus paper turns blue Bromothymol blue turns blue Methyl orange turns yellow
Common bases:
Sodium hydroxide NaOH making soap; drain cleaners
Potassium hydroxide KOH battery electrolyte
Calcium hydroxide Ca(OH)2 making plaster and drywall
Magnesium hydroxide Mg(OH)2antacids
Solutions of acids and bases
pH scale (page 277) A numerical scale developed to
measure the relative strengths of acids and bases
Ranges from 0 to 14 0 is the strongest acid 14 is the strongest base.
What happens when an acid and a base combine? Always forms water and a salt. Salt = ionic compound formed when a
positive ion of a base combines with a negative ion of an acid.
Neutralization. These are double replacement
reactions.
What determines if an acid is classified as “strong” or weak? Which is stronger? 1 M acetic acid or
1M hydrochloric acid? Strength is determined by how well the
acid or base dissociates into solution. Strong acids and strong bases are good
electrolytes.
Strong and Weak vs. Dilute and Concentrated Strong and weak refer to how well an
acid or base create ions in solution. If a large percentage of the molecules break up, then it is strong. If not, it is weak.
Dilute and Concentrated refer to the percentage of the solution that is made up of the solute.