Semester 2 Exam Chem

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Reaction Stoichiometry

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154 Terms

1

Reaction Stoichiometry

The study of materials consumed & produced in chemical reactions

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In stoichiometry, what do you use to balance equations?

Coefficients

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Mole rations are known as _____?

Conversion factors

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What do mole ratios help predict?

The amount of reactants & products in a balanced equation

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How are mole ratios formed?

Coefficients

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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

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Limiting Reactant

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

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Excess Reactant

The reactant that does not run out

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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

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Theoretical Yield

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

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Actual Yield

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

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Percent Yield Equation

Actual Yield / Theoretical Yield x 100

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Heat

A measure of the total kinetic energy of a system

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Temperature

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

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Phase Diagram

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

<p>A graph of pressure versus temperature that shows the conditions under which phaSes of a substance exist</p>
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Triple Point

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

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Critical Point

The critical temperature and pressure

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Critical Temperature

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

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Critical Pressure

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

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Melting Phase

Solid → Liquid

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Vaporization Phase

Liquid → Gas

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Sublimation Phase

Solid → Gas

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Condensation Phase

Gas → Liquid

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Crystallization Phase

Liquid → Solid + Crystals

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Deposition

Gas → Solid

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Endothermic

Absorption of heat/energy

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Exothermic

Release of heat/energy

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When will a liquid boil?

When vapor pressure = atmospheric pressure

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Boiling Point

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

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Heating Curve

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Heating Curve Equations

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Heat Lost = Heat Gained Equation

m x c △ t = m x c △ t

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What are the 3 most common physical states of matter?

  1. Solid

  2. Liquid

  3. Gas

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34

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

Particles of matter are always in motion

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What 2 properties is the kinetic molecular theory based upon?

  1. Energy of particles

  2. Forces between particles

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Ideal Gas

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

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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

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Do Ideal Gases exist?

No

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Why are gases and liquids considered to be fluids?

Gas particles slide past one another

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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

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Why are gases compressible?

Volume can be reduced

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Diffusion

Mixing of gases in air

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Effusion

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

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What is a real gas?

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

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

  1. Moles

  2. Volume

  3. Temperature

  4. Pressure

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Volume

The amount of space an object occupies

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Pressure

The amount of force applied per area on a surface

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What are the SI units for pressure?

  1. atm (atmosphere)

  2. mmHg (millimeters of mercury)

  3. Pa (pascal)

  4. Torr (torr)

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Barometer

Measures the atmospheric pressure

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Who introduced the first barometer?

Evangelista Torricelli

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What are STP conditions?

0° & 1 atm

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Standard Units of Pressure Conversions

1 atm = 760 mmHg = 760 torr = 101.325 kPa

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What are gas laws?

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

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Boyle’s Law

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

Equation: P1 x V1 = P2 x V2

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Charle’s Law

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

Equation: V1/T1 = V2/T2

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Before calculating, the temperature must be in ____?

Kelvin

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How do you find Kelvin?

Kelvin (K) = °C + 273

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How do you find °C?

°C = Kelvin - 273

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Gay-Lussac’s Law

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

Equation: P1/T1 = P2/T2

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Combined Gas Law

Expresses all variables with a constant of number of moles

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

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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 …

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Dalton’s Formula

PT = P Gas + P H2O

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

temperature, pressure

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

small whole number ratios

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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

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

molecules

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

moles

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Standards Molar Volume of a Gas at STP

1 mole gas = 22.4 L

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Ideal Gas Law

A mathematical relationship that helps describe gas behavior

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Variables Needed in the Ideal Gas Law

  1. P

  2. V

  3. T

  4. n (# of moles)

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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)

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Ideal Gas Law Constant

R

  • R = 0.0821 atm/mol k

  • R = 8.314 kPa/mol k

  • R = 62.4 mmHg/mol k

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Graham’s Law

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

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Homogeneous Solution

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

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Can particles be seen?

No

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Solute

Substance being dissolved

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Solvent

Substance doing the dissolving

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Soluable

Capable of dissolving

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Insoluable

Not capable of dissolving

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Suspensions

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

  • Can be filtered

  • Example: Muddy water

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Colloids

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

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Heterogeneous

Microscopic scale under a microscope

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Homogeneous

Macroscopic scale under a microscope

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The Tyndall Effect

Colloids scatter light, making a beam visible

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Can solutions scatter light?

No

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Electrolyte

A substance whose aqueous solution conducts an electric current

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Nonelectrolyte

A substance whose aqueous solution does not conduct an electric current

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

It is determined by the type of bond for the compound

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89

Dissociation

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

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Can ionic compounds dissociate?

Yes

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Ionization

The formation of ions

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Can polar-covalent compounds ionize?

Yes

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93

What is the general rule for solute-solvent interactions?

Like dissolves like

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94

Like dissolves like examples

  • Polar dissolves polar

  • Non-polar dissolves non-polar

  • Polar also dissolves ionic

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Hydration

The attraction between water molecules and the ions dissolved

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Immiscible

Liquids that are not soluble in each other

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Miscible

Liquids that dissolve freely in each in any proportion

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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

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Saturated Solution

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

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Unsaturated Solution

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

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