Solutions. Mixtures A substance made up of 2 or more elements or compounds that are not chemically combined and can be separated 2 classifications 1.

Solutions

Mixtures

• A substance made up of 2 or more elements or compounds that are not chemically combined and can be separated

• 2 classifications1. Homogeneous--> mixtures that are spread out evenlyEx. solutions2. Heterogeneous--> mixtures are not spread out evenlyEx. Colloids and suspensions

KoolAid & Salt Water are examples of Homogeneous

Mixtures

Rice Krispy Bars, Paint & Pizza are examples of Heterogeneous Mixtures

What is a solution?

• A homogeneous mixture • Ex. saltwater• Made of 2 parts• 1. Solute--> the substance that is

considered to be dissolved (salt)• 2. Solvent--> the substance in which

the solute is dissolved (H2O)

How can you tell which is the solute and solvent?

• If 2 substances in the solution were in different phases, the one that changed phase is the solute (salt), and the substance that did not change phase is the solvent (H2O)

• If 2 substances are in the same phase originally, the substance in smaller amount is usually the solute (40 g alcohol), and the substance is greater quantity is usually the solvent (60 g H2O)

Which is the solute and solvent?

• 75% Cu and 25% Zn = brass alloy

• CO2(g) and H2O(l) =

carbonated beverage

• O2(g) and air

Properties of Solutions

• Very small particle size: .01 nm-1 nm

• Do not separate upon standing

• Are transparent

• Cannot be separated by filtration

• Particles do not display the Tyndall Effect: the particles are too small to scatter light

Examples of Solutions

• Sucrose in H2O

• Food coloring in H2O

• Sodium Borate in H2O

• Carbonated Beverages

• Alloys (2 or more metals)

• H2O vapor in air

Colloids

• A heterogeneous mixture• May or may not be transparent• Medium particle size: 1 nm -1000 nm• Do not separate upon standing• Cannot be separated by filtration• Particles display the Tyndall Effect: the

particles are large enough to scatter light

Examples of Colloids

• Gelatin in H2O

• Milk

• Clouds

Suspensions

• A heterogeneous mixture

• Are not transparent

• Large particle size: over 1000 nm

• Particles settle out

• Can be separated by filtration

• May or may not display the Tyndall Effect

Examples of Suspensions

• Clay in H2O

• Cooking oil in H2O

• Spoiled milk

More about Solutions

• Solutions in which H2O is the solvent are called aqueous

• If H2O cannot act as the solvent, another liquid will

Ex. CCl4 & C6H6 will act as fat solvents in the body

• Solutions in which alcohol is the solvent are called tinctures

Ex: Betadine solution (I2 crystals dissolved in CH3OH)

• When 2 liquids dissolve in one another, they are said to be miscible

• When 2 liquids do not dissolve in one another, they are said to be immiscible

• Make sure to use these terms when describing the solubility of liquids in one another!!!

• Ex. Ethanol is miscible in H2O• Ex. Oil is immiscible in H2O

• Alloys are solutions made up of 2 or more metals

• Ex. Brass 70%Cu and 30% Zn

• Ex. Sterling silver (Cu & Silver)

• Ex. Amalgam--> an alloy made Hg and other metals that is used to make dental fillings

Why can we make so many aqueous solutions?

• H2O is known as the “universal solvent” because it can dissolve or be miscible with most polar substances

• ***Remember the “Like” dissolves “like” rule

• Polar substances have an unequal distribution of electron charge because of certain elements stronger or weaker desires to become a noble gas within the compound

• Ex. NaCl, C12H22O11, ethanol (C2H5OH)

• Nonpolar substances have equal distribution of electron charge because all elements within the compound have the same desire to become a noble gas

• Ex. Kerosene (CxHy), oil, ethane (C2H6)

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What makes something an electrolyte?

• An electrolyte is a substance that dissolves in H2O that conducts an electric current

• A substance must have ions (+ and - charged particles) to be an electrolyte

• Electrolytes may be classified as “strong” or “weak” depending on how many ions they produce in solution

• Examples include: sodium chloride (NaCl), potassium phosphate (K3PO4)

• A nonelectrolyte is a substance that dissolves in H2O that does not conduct an electric current

• Nonelectrolytes are polar or nonpolar covalent compounds.

• Examples include: sucrose C12H22O11 (polar), pure water H2O (polar), and iodine I2 (nonpolar)

How can we increase the rate of dissolution?

• Rate of Dissolution--> the measure of how fast a substance dissolves

• Increase surface area of solute• Increase the temperature• Agitate the solution (stir)• Increase the concentration of solvent so more

particles come in contact with the solute

What is solubility?

• Solubility is the maximum amount of solute that can dissolve in a certain amount of solvent

• What main factors affect solubility?• 1. Temperature• 2. Pressure• 3. Nature of the solute (polar vs. nonpolar)

Temperature as a factor

• As you increase the temperature of a solid or liquid, solubility increases

By increasing the kinetic energy, the solvent particles are forced to come in contact with the solute particles more often and can take on more as a result

• As you increase the temperature of a gas, solubility decreases

By increasing the kinetic energy, the gas particles are moving too quickly and leave the solution before they have a chance to collide with the solute (gases do not want to be put in a liquid solution!!!)

Pressure as a factor

• An increase or decrease in pressure of a solid or liquid in solution will have no affect on the solubility of that solution

This is because there is little to no ability (or space between particles) to compress or expand solid or liquid

• An increase in pressure will increase the solubility of a gas

This is because gas particles can be forced closer together (or farther apart) due to the large spacing between particles

What is saturation?

• When a solution has the maximum amount of solute dissolved in a certain amount of solvent at a given temperature, it is said to be saturated

• Saturated solutions are said to be in equilibrium

• rate of solute dissolving in solvent rate of solute crystallizing in solvent

Solubility Curve

All data points on the line represent a

saturated solution

Unsaturated versus Saturated Solutions?

• When a solution contains less solute than it could at a certain temperature, it is said to be unsaturated

• When a solution contains more solute than it normally could at a certain temperature, it is said to be supersaturated

***This is a dynamic condition that is very unstable

Solubility Curve

All data points above the saturation line represent a

supersaturated solution

All data points below the saturation line represent an unsaturated solution

Solubility Curve for Gases

• Gases have too much kinetic energy and do not want to be dissolved in a liquid

• When temperature increases, solubility decreases for gases

More on gases…

• Henry’s Law--> the solubility of gases in a liquid is directly proportional to the partial pressure of that gas on the surface of that liquid

• Effervescence--> the rapid escape of gas from a liquid in which it dissolves

Dilute Versus Concentrated Solutions

• Dilute--> a low amount of solute is dissolved in a solvent

• Concentrated--> a high amount of solute is dissolved in a solvent

• These terms will not tell us whether a solution is saturated, unsaturated, or supersaturated

• The concentration of a solution can be found using the Molarity (M) and Molality (m) equations

Molarity

• M = moles of solute / L of solution

• Solution = solute + solvent

• Sample problem : How many grams of sodium chloride can be dissolved in 150. mL of water to make a .85 M solution?

• What is the molarity of a solution made up of 150. mL of ethanol (C2H5OH) in 200. mL of water? Dethanol = .789 g/mL, Dwater = 1.00 g/mL

Molality

• m = moles of solute / kg of solvent

• Sample problem : How many grams of CCl4 are needed to dissolve 28 g of I2 to make a .050 m solution?

• A solution containing 468 g of sucrose (C12H22O11) per liter has a density of 1.18 g/mL. What is the molality of this solution?

How to make a dilute solution from a concentrated solution?

M1V1 = M2V2

M = molarity

V = volumeSample problem: How much 12 M HCl do you need to

make 500. mL of a 3.0 M HCl solution? How much water did you add to the concentrated 12 M solution?

concentrated dilute

• How much water would you need to make .850 L of 6.8 M sulfuric acid solution for 18 M solution?