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Solutions, Acids, and Bases

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.

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Solutions, Acids, and Bases

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  1. Solutions, Acids, and Bases Chapter 7

  2. Solute The substance that is dissolved into the solution. examples: Sugar in kool-aid Salt in salt water CO2 in pop Solvent The substance that does the dissolving in a solution. examples: Most common is water. Parts of a solution

  3. Dissolving • Three ways to dissolve a solute in a solvent: • Dissociation • Dispersion • Ionization

  4. 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

  5. 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

  6. 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

  7. Concentrated A large amount of solute dissolved in a solvent Dilute A little bit of solute dissolved in a solvent Concentration

  8. 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.

  9. Supersaturation example: • Sodium acetate in water. • Used in commercial hand warmers.

  10. Insoluble • A substance that will NOT dissolve in water.

  11. “Like dissolves like” • Nonpolar solvents will dissolve nonpolar solutes. • examples: benzene & acetone • Polar solvents will dissolve polar solutes

  12. 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. 2 factors that affect solubility:

  13. Specific concentration • Can be defined as percent by volume or percent by mass • Example: 3% hydrogen peroxide or 25% fruit juice.

  14. Acids • Very important chemicals in everyday life processes.

  15. Properties of acids: • Sour taste (never taste a chemical) • All contain hydrogen • Also called “proton donors” • React with active metals to produce hydrogen gas. Zn + 2HCl ZnCl2 + H2

  16. Indicators • Chemicals used to identify acids and bases by changing color. • ACIDS: • Litmus paper (blue to red) • Phenolphthalein (colorless) • Methyl Orange (orange to red) • Bromothymol Blue (changes to yellow)

  17. Common acids • Sulfuric (H2SO4) used in car batteries • Nitric (HNO3) also fertilizers • Hydrochloric (HCl) stomach acid • Carbonic (H2CO3) carbonated drinks • Acetic (HC2H3O2) vinegar

  18. Also very important in everyday processes. Bases

  19. 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

  20. 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

  21. 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.

  22. 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 happens when an acid and a base combine?

  23. 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.

  24. 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.

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