Semester 2 Exam Chem

Reaction Stoichiometry

Reaction Stoichiometry

The study of materials consumed & produced in chemical reactions

In stoichiometry, what do you use to balance equations?

Coefficients

Mole rations are known as _____?

Conversion factors

What do mole ratios help predict?

The amount of reactants & products in a balanced equation

How are mole ratios formed?

Coefficients

4 Steps to Stoichiometry Calculations

1. Balance The Equation

2. Convert Given into Moles

3. Use Coefficients for Mole Ratio

4. Convert the Substance Needed Into Grams

Limiting Reactant

The reactant that is consumed (runs out) first; limits the amount of products formed

Excess Reactant

The reactant that does not run out

Steps for determining limiting & excess reactants

1. Write a balanced chemical equation

2. Identify all given quantities

3. Solve for one of the products based on all given quantities

4. Cross out the larger amount of the products produced

5. Larger amounts indicate the excess reactants

6. The smaller amount of the product indicates the limiting reactant

7. The smaller amount of the product is the theoretical yield

Theoretical Yield

The maximum produced from a balanced chemical equation based on 100% efficiency

Actual Yield

The amount obtained in a laboratory setting. Rarely 100% due to sources of error.

Percent Yield Equation

Actual Yield / Theoretical Yield x 100

Heat

A measure of the total kinetic energy of a system

Temperature

A measure of the average amount of kinetic energy of a system

Phase Diagram

A graph of pressure versus temperature that shows the conditions under which phaSes of a substance exist

Triple Point

Indicates the temperature and pressure at which a solid, liquid & gas can coexist at equilibrium

Critical Point

The critical temperature and pressure

Critical Temperature

The temperature above which the substance cannot exist in a liquid state

Critical Pressure

The lowest pressure at which the substance can exist as a liquid at it’s critical temperature

Melting Phase

Solid → Liquid

Vaporization Phase

Liquid → Gas

Sublimation Phase

Solid → Gas

Condensation Phase

Gas → Liquid

Crystallization Phase

Liquid → Solid + Crystals

Deposition

Gas → Solid

Endothermic

Absorption of heat/energy

Exothermic

Release of heat/energy

When will a liquid boil?

When vapor pressure = atmospheric pressure

Boiling Point

The temperature at which the equilibrium vapor pressure of the liquid equals the atmospheric pressure

Heating Curve

Heating Curve Equations

Heat Lost = Heat Gained Equation

m x c △ t = m x c △ t

What are the 3 most common physical states of matter?

1. Solid

2. Liquid

3. Gas

What does the kinetic molecular theory state about the make-up of matter?

Particles of matter are always in motion

What 2 properties is the kinetic molecular theory based upon?

1. Energy of particles

2. Forces between particles

Ideal Gas

A hypothetical gas that perfectly fits all assumptions of the kinetic molecular theory

The five assumptions of the kinetic molecular theory of gases

1. Gases consist of many particles that are spread apart relative to their size

2. Collisions between particles and the walls of the container are elastic

3. Gas particles are in continuous, rapid, random motion and therefore have kinetic energy

4. There are NO forces of attraction or repulsion between gas particles

5. The average amount of kinetic energy depends on the temperature of the gas

Do Ideal Gases exist?

No

Why are gases and liquids considered to be fluids?

Gas particles slide past one another

Why do gases have such low density as compared to solids or liquids?

The particles are very far apart compared to solids & liquids and the volume is greater

Why are gases compressible?

Volume can be reduced

Diffusion

Mixing of gases in air

Effusion

Mixing of gases in a piece of lab glassware particles passing through a tiny opening

What is a real gas?

A gas that does not behave completely according to the kinetic molecular theory

What four measurable quantities are needed to describe a gas fully?

1. Moles

2. Volume

3. Temperature

4. Pressure

Volume

The amount of space an object occupies

Pressure

The amount of force applied per area on a surface

What are the SI units for pressure?

1. atm (atmosphere)

2. mmHg (millimeters of mercury)

3. Pa (pascal)

4. Torr (torr)

Barometer

Measures the atmospheric pressure

Who introduced the first barometer?

Evangelista Torricelli

What are STP conditions?

0° & 1 atm

Standard Units of Pressure Conversions

1 atm = 760 mmHg = 760 torr = 101.325 kPa

What are gas laws?

Mathematical relationships between the 4 variables for gases: Pressure, Temperature, Volume, Moles

Boyle’s Law

Volume and pressure are inversely related with a constant temperature & number of moles

Equation: P1 x V1 = P2 x V2

Charle’s Law

Volume and temperature are directly related with a constant pressure & number of moles

Equation: V1/T1 = V2/T2

Before calculating, the temperature must be in ____?

Kelvin

How do you find Kelvin?

Kelvin (K) = °C + 273

How do you find °C?

°C = Kelvin - 273

Gay-Lussac’s Law

Pressure and temperature are directly related with a constant volume & number of moles

Equation: P1/T1 = P2/T2

Combined Gas Law

Expresses all variables with a constant of number of moles

Equation: P1 x V1 / T1 = P2 x V2 / T2

Dalton’s Law of Partial Pressures

The total pressure of a mixture is equal to the sum of all partial pressures

Equation: PT = P1 + P2 + P3 …

Dalton’s Formula

PT = P Gas + P H2O

Gay-Lussac noticed gas volume relationships at a constant ____ and ____

temperature, pressure

Gay-Lussac noticed (small whole number ratios, one whole number ratios) by volume for the reaction of gases

small whole number ratios

Gay-Lussac’s Law of Combining Volumes

At a constant temperature and pressure, the volumes of reactants & products can be expressed as small whole-number ratios

Equal volumes of all gases under the same conditions of temperature & pressure contain the same number of ____?

molecules

Avagadro proved a direct relationship existed between volume and the number of ____?

moles

Standards Molar Volume of a Gas at STP

1 mole gas = 22.4 L

Ideal Gas Law

A mathematical relationship that helps describe gas behavior

Variables Needed in the Ideal Gas Law

1. P

2. V

3. T

4. n (# of moles)

Ideal Gas Law Equations

1. PV = nRt (n= moles)

2. PV = mRt/M (m = mass (g) & M = molar mass)

3. D = MP/RT (D= density)

Ideal Gas Law Constant

R

• R = 0.0821 atm/mol k

• R = 8.314 kPa/mol k

• R = 62.4 mmHg/mol k

Graham’s Law

Rate A / Rate B = √Molar Mass B / √Molar Mass A

Homogeneous Solution

Mixture of 2 or more substances that appear to look the same

Can particles be seen?

No

Solute

Substance being dissolved

Solvent

Substance doing the dissolving

Soluable

Capable of dissolving

Insoluable

Not capable of dissolving

Suspensions

• The particles are so large that they settle out of the solvent in not constantly stirred

• Can be filtered

• Example: Muddy water

Colloids

The particle is intermediate in size between those of suspension and those of a solution

Heterogeneous

Microscopic scale under a microscope

Homogeneous

Macroscopic scale under a microscope

The Tyndall Effect

Colloids scatter light, making a beam visible

Can solutions scatter light?

No

Electrolyte

A substance whose aqueous solution conducts an electric current

Nonelectrolyte

A substance whose aqueous solution does not conduct an electric current

Why do some compounds conduct electricity in solution but others don’t?

It is determined by the type of bond for the compound

Dissociation

The seperation of ions. The ions are already present at the beginning due to the ionic bond.

Can ionic compounds dissociate?

Yes

Ionization

The formation of ions

Can polar-covalent compounds ionize?

Yes

What is the general rule for solute-solvent interactions?

Like dissolves like

Like dissolves like examples

• Polar dissolves polar

• Non-polar dissolves non-polar

• Polar also dissolves ionic

Hydration

The attraction between water molecules and the ions dissolved

Immiscible

Liquids that are not soluble in each other

Miscible

Liquids that dissolve freely in each in any proportion

Factors Effecting Solubility

1. Increasing surface area, stirring/shaking, or temperature increases the rate of dissolution (dissolving)

2. Solution Equilibrium- dissolving and crystallizing at the same rate in a closed system

Saturated Solution

A solution that contains the maximum amount of solute that may be dissolved under existing conditions

Unsaturated Solution

A solution that contains less solute than a saturated solution under existing conditions