Semester 2 Exam Chem

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154 Terms

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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
A graph of pressure versus temperature that shows the conditions under which phaSes of a substance exist
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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
knowt flashcard image
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Heating Curve Equations
knowt flashcard image
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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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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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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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What is the general rule for solute-solvent interactions?
Like dissolves like
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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