Chapter 6Solutions, Acids, and Bases

• Chapter Preview:• 6.1) Solutions and Other

Mixtures:– Heterogeneous Mixtures– Homogeneous Mixtures:

• 6.2) Dissolving and Solubility:– The Dissolving Process – Water: A Common Solvent– Concentration

• 6.3) Acids, Bases, and pH:– What are Acids?– What are Bases?– How Acidic Is and Acid?– Neutralization Reaction

• 6.4) Acids and Bases In the Home:– Cleaning Products– Other Household Acids and

Bases

Section 6.1: Solutions and Other Mixtures

• Objectives: distinguish between homogeneous mixtures and heterogeneous mixtures.

• Compare and contrast the properties of solutions, colloids, and suspensions.

• Identify ways to separate different kinds of mixtures.

Heterogeneous Mixtures:

• A heterogeneous mixture, such as fruit salad is not the same throughout.

• Suspension: a mixture that looks uniform when stirred or shaken that separate into different layers when it is no longer agitated. Particles size of about 1000 nm.

• Colloid: a mixture of very tiny particles of pure substances that are dispersed in another substance but do not settle out of the substance. Particles size from 1 to 100 nm in diameter.

Heterogeneous Liquid – Liquid Mixtures:

• When oil is mixed with vinegar to make salad dressing, two layers form.

• Immiscible: when two liquid don’t mix.

• Emulsion: any mixture of immiscible liquids in which the liquids are spread throughout one another.

Homogeneous Mixtures:

• Homogeneous Mixtures not only look uniform, they are uniform.– For example: salt water, kool –aid,

and lemonade, etc.

Solutions are homogeneous mixtures:

• Solution: a homogeneous mixture of two or more substances uniformly spread throughout a single phase.

• Solute: the substance that dissolves in a solution.

• Solvent : the substance that dissolves the solute to make a solution.

• Miscible liquids mix to form solutions.

• One way to separate miscible liquids is by a process called distillation. For example water mixes with isopropanol to make a solution of rubbing alcohol.

Section 6.1 Summary Report

• A heterogeneous mixture is a nonuniform blend of two or more substances.

• The particles in a suspension soon settle out of the mixture.

• The dispersed particles in a colloid are smaller and do not settle out.

• An emulsion is a colloid in which liquids that normally do not mix are spread throughout one another.

• A homogeneous mixture, or solution, is a uniform blend of two or more substances.

• In a solution, the solute is dissolved in the solvent.

Section 6.2Dissolving and Solubility

• Describe how a substance dissolves in of its solubility, molecular motion, and solute-solvent interactions.

• Identify several factors that affect the rte at which a substance dissolves.

• Relate the structure of water to its ability to dissolve many different substances.

• Distinguish between saturated, unsaturated, and supersaturated solutions.

The Dissolving Process

• According to the kinetic theory, the water molecules in each glass of tea are always moving.

• Some moving water molecules collide with sugar crystals.

• When this happens, energy is transferred to the sugar molecules at the surface of the crystal.

• Solutes with a larger surface area dissolve faster.

• Stirring or shaking a solution helps the solute dissolve faster.

• Solutes dissolve faster when the solvent is hot.

• Not every substance dissolves.– Soluble in water– Insoluble in water

Water: A Common Solvent

• Two-thirds of Earth’s surface is water.• The liquids you drink are mostly water.• Water is colorless and tasteless.• Water is sometimes called the universal solvent.

Characteristics of Water:

• The structure of water helps it dissolve charged particles:

• “Like dissolves like”:– Water can dissolve many substances, but there are many others it

can’t dissolve.– For example, olive oil doesn’t dissolve in water, and neither does

gasoline. That because its components are non-polar, meaning their molecules do not have partial charges on opposite ends.

Concentration

• You can make a solution by dissolving sodium acetate in water. But how much sodium acetate do you need to add?

• Concentration: the quantity of solute dissolved in a given quantity of solution.

Types of Solutions:

Unsaturated Solution: a solution that is able to dissolve more.

Saturated solution: a solution that cannot dissolve any more solute at the given condition.

• Supersaturated solution: a solution holding more dissolved solute than is specified by its solubility at a given temperature.

Section 6.2 Summary Report

• The larger the surface area a solute has, the faster it will dissolve.• Stirring or shaking the solution dissolves solutes faster.• Heating a solvent also dissolves solutes faster.• So many substances are soluble in water that it is sometimes called the

universal solvent.• An unsaturated solution can dissolve more solute.• A saturated solution cannot dissolve any more solute.• A solute’s solubility is exceeded in a supersaturated solution.

Section 6.3 Acids, Bases, and pH

• Objectives:– Compare and contrast acids and bases.– Relate the pH of a solution to the concentration and strength of

dissolved acid or base.– Identify the products of neutralization reactions.

What are Acids?

• Acid: a substance that donates hydrogen ions, H+, to form hydronium ions, H3O+, when dissolved in water.

– Sour– Conduct electricity and heat– Turn litmus paper from blue to red– Examples; lemon, lime, dill pickles, etc.

What are Bases?

• Base: a substance that either contains hydroxide ions, OH-, or reacts with water to form hydroxide ions.

• Bitter• Conductors of electricity and heat.• Turn litmus paper from red to blue.

How Acidic Is an Acid and How Basic Is a Base?

• pH: a measure of the hydronium ion concentration in a solution.• The pH values correspond to the concentration of hydronium ions.• Small differences in pH values mean larger differences in hydronium ion

concentration.

Neutralization Reactions:

• Neutralization reaction: a reaction in which hydronium ions from an acid and hydroxide ions from a base react to produce water molecules.– Note: strong acids and bases react to form water and a salt.– Note: some acid-base reactions do not result in neutral solutions.

Section 6.3 Summary Report

• Acids are sour, corrosive substances that form hydronium ions when dissolved in water.

• Bases are bitter, slippery substances that either contain hydroxide ions or form them when dissolved in water.

• Indicators are substances that change color depending on whether a solution is acidic, basic, or neutral.

• Neutral solutions have a pH of 7, acidic solutions have a pH of less that 7, and basic solutions have a pH of greater than 7.

• A neutralization reaction occurs when hydronium ions and hydroxide ions react to form water molecules.