General Test 2 – Flashcards

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What is the molar mass of any gas at STP?

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22.4 L

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What is STP?

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Standard Temperature and Pressure

 

Temp:273 K

Pressure: 1atm

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The total pressure of our atmosphere is equal to

the sum of the pressures of which gases?

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N2 and O2

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Do nonpolar or polar gases behave more ideally?

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Nonpolar because attractive forces are present in polar gases.

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What is a surfactant?

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A substance added which decreases surface tension.

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What is the triple point?

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The temp and pressure at which a substance can exist in equilibrium in the liquid, solid and gas state.

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Evaporation

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The process of conversion of a liquid to gas at a temp too low to boil.

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Condensation

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Conversion of gas to the liquid state.

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 Liquid water in equilibrium with water vapor.

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When the rate of evaporation equals the rate of condensation, the system is at equilibrium.

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Vapor pressure of a liquid

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the pressure exerted by the vapor at equilibrium

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Boiling point

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the temp at which the vapor pressure of the liquid becomes equal to the atmostpheric pressure.

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What happens when you go to a mountain where the atmpospheric pressure is lower than 1 atm?

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The boiling point lowers

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What are the 2 Van der Waals subtypes?

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Dipole-Dipole interactions- attractive forces between polar molecules.

 

London forces- as electrons are in continous motion, a nonpolar molecule could have and instantaneous dipole.(short-lived)

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Characteristics of London forces

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-Exist between all molecules.

-the only attractive force between nonpolar atoms or molecules.

-electrons are in constant motion

-the temporary dipole interacts with other temporary dipoles to cause attraction.

 

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Hydrogen Bonding

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-not a van der waals force

-type of dipole-dipole

-causes higher than expected b.p and m.p

 

Requirements: molecules have hydrogen directly bonded to O, N, or F 

 

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Joule Thompson Effect

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When a gas under pressure is allowed to escape into a lower pressure, cooling occurs

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Critical temperature

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the temp at which the substance will become a gas under any pressure.

 

Gases liquify under sufficient pressure if their temp is under the critical temp.

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The solid state structures
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crystalline solid-regular repeating structure. ((diamond, NaCl)
amorphous solid-no organized structure(glass,plastic,concrete)
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Types of crystalline solids
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Ionic solid
covalent solid
molecular solid
metallic solid
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Ionic solid
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-held together by electrostatic forces
-high m.p and b.p
-hard and brittle
-dissolves in water,electrolytes(NaCl)
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Covalent solid
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-held together by covalent bonds
-high m.p and b.p
-extremely hard(diamond)
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molecular solid
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-held by intermolecular forces
-often soft
-low m.p
-often volatile(ice)
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Metallic solids
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-metal atoms held with metal bonds(overlap of orbitals of metal atoms)
-this causes area of high electron density where e- are extremely mobile
-conducts electricity
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Kinetic molecular theory of gases

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1.the atoms or molecules are in constant, random motion.

2.a gas is mostly empty space

3.all of the atoms and molec behave independently.

4.they collide with each other and the walls of container without losing energy. energy is transferred from one atom to another.

5. the avg kinetic energy increases or decreases in proportion to absolute temp.

 

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Properties of gases and the kinetic molecular theory

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-gases will expand to fill any available volume.

-gases have low density

-gases readily diffuse through each other.

-gases exert pressure on their containers.

-gases behave ideally at low pressures and high temperatures.

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Solute

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the substance present in the largest quantity.

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Solvent in Air
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Nitrogen
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Properties of Liquid solutions
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-Clear, transparent, no visible particles

-may have color

-volumes of solute and solvent are not additive

-non electrolytes do not dissociate

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Colloidal suspension
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-solute particles which are not uniformly distributed

-appears identical to solution form the naked eye.

-smaller than 1nm, have solution

-Larger than 1nm, have a precipitate

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Tyndall Effect

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-the ability of a colloidal suspension to scatter light.

- there is a haze

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True solution
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the solute cannot be isolated from the solution by filtration.
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Solubility
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How much of a particular solute can dissolve in a certain solvent at a specified temperature.
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Factors that affect solubility
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1. Polarity of solute and solvent(the more different they are, the lower the solubility.

2.Temperature

3.Usually has no effect unless pressure is on gas in a liquid, directly proportional to applied pressure.

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Supersaturated solution
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on cooling, the excess solute may remain in solution for a time.(inherently untable)  with time the excess solute will precipitate ansd the solutjion will revert to a saturated solution.
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Saturated solution
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a solution that is in equilibrium with undissolved solute.
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Henry's Law
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The gas solubility is directly proportional to the pressure of that gas in the atomosphere that is in contact with the liquid.
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What temperatures are gases most soluble in?

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Low temperatures

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-solubility decreases significantly at higher temperatures.

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In a dilution will the number of moles of solute change?
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No, only fewer per unit
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What are the two ways of expressing concentration of ions in solution?
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Moler per liter (molarity)

;

or

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Equivalents per liter (eq/L) --emphasis on charge

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Colligative property
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properties of solutions that depend on the concentration of the solute particles, rather than the identity of the solute.
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Name the four colligative properties

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1.Vapor pressure lowering

2.Boiling point elevation

3.freezing point depression

4.osmotic pressure

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Vapor pressure lowering(colligative prop #1)

 

Describe

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Raoult's law- when a nonvolatile solute is added to a solvent, vapor pressure of the solvent decreases in proportion ot the concentration of the solute.

 

-solute molecules serve as a barrier to the escape of solvent molecules resulting in a decrease in the vapor pressure.

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Freezing point depression(colligative prop #2)
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Solute molecules interfere with the rate at which liquid water molecules associate to form the solid state.

 

-an equal conc of NaCl will affect the f.p. twice as much as glucose.(NaCl 2 particles, glucose 1)

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Boiling point elevation (colligative prop #3)

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If a solute is present, the increase in boiling temp is necessary to raise the vapor pressure to atmospheric pressure.

 

-an electrolyte will affect the boiling point to a greater degree than a nonelectrolyte of the same concentration.

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Is molarity or molality temperature dependant?
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Molarity is temp dependant because volume is temp dependant.
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Osmotic Pressure (colligative prop #4)
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the pressure that must be exerted to stop the flow of water across a selectively permeable membrane by osmosis.

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se
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Semipermeable membrane
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membrane permeable to solvent but not to solute.
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Osmosis
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the movement of solvent form a dilute solution to a more concentrated solution through a semipermeable membrane.
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Osmolarity

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The molarity of particles in solution.

 

mol particle/L

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Isotonic solution
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have identical osmotic pressures and no osmotic pressure difference across the cell membrane.

Osmolarity inside the cell and outside are the same.

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Hypotonic solution
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Solution has a lower osmolarity than the cytoplasm of the cell and this causes a shift of water from soln to cell causing it to burst, hemolysis.
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Hypertonic solution
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solute concentration of fluid higher than inside the cell causing water to flow into the surrounings  causing crenation(collapse)

 

water will move from area of higher conc to lower.

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What are the two most important cations in the environment?
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Na and K
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Signs of increased Na+
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confusion, stupor, or coma
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Signs of Na+ too loww
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decreased urine output, dry mouth, flushed skin and fever.
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Signs of high or low K+
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both can cause death by heart failure.
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Important anions in the blood
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Cl- and HCO3-

 

Cl-acid/base balance, maintnance of osmotic pressure, and oxygen transport by hemoglobin.

 

HCO3-  Form in which most waste CO2 is carried out of the body.

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Proteins in the blood
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-blood clotting factors

-antibodies

-albumins(carriers of nonpolar substances which cannot dissolve in water)

-Proteins are transported as a colloidal suspension

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Kinetic molecular theory
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-molecules and atoms a reaction mixture are in constant random motion

-they frequently collide with each other

-some collisions, those with sufficient energ, will break bonds in molecules

-when bonds are broken, new bonds may be formed and products result

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Calorimetry
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Experimantal strategies for measuring temperature change and calculating heats of reactions.
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How is energy measured in a chemical reaction?
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the absolute value for energy stored in a chemical system cannot be measured.

 

-the change in energy during these chemical changes can be measured.

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Law of conservation of energy
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energy of the universe is constant
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Exothermic reaction
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If the energy required to break the bonds of the reactants is less than energy to form the bonds of the products then there is excess energy.
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endothermic reaction

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If the energy required to break the reactant bonds is greater than the energy released to form the products bonds the reaction will need and external supply of energy.
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Enthalpy
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represents heat energy

 

energy release= (-) exothermic

energy absorbed=(+) endothermic

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Second law of thermodynamics
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states that the universe spontaneously tends toward increasing disorder or randomness.

 

high entropy- disordered

low entropy-well organized

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Spontaneous reactions
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occur without any external energy input.

 

-most are exothermic

-higher in entropy(more disorganized)

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Nonspontaneous reaction
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-usually endothermic

-products with lower entropy

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Processes that have positive entropy
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melting, vaporization, and dissolution
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Kinetics
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the study of the rate of chemical reactions
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Effective collision
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a collision that produces product molecules.

-only effective collisions lead to chemical reaction.

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Activated complex
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an unstable state that the reaction proceeds from reactants to products.

-this cannot be isolated.

 

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activation energy

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is the difference between the energy of the reactants and that of the activated complex.
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electrolysis
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when an electrical current is passed through water.
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Factors that affect reaction rate
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-structure of the reacting species

-molecular shape and orientation

-concentration of reactants

-temp of reactants

-physical state of reactants

-presence of a catalyst

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Structure of reacting species
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-oppositely charged species react faster(dissociated ions, very low activation energy.

-ions with same charge do not react

-large molecules may obstruct the reactive part of the molecule.

-only molecular collisions with correct orientation lead to product formation.

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The concentration of reactants(affect rate)
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-rate will increase as concentration increases .

 

IE: more collisions per unit time and more reactant per unit volume.

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The temperature of reactants(affect rate)

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-rate increases as the temp increases

 

-increased kinetic energy, inc speed of particles, more collisions

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What physical state does a reaction proceed fastest in?

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Liquid>Gas>Solid

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How does the presence of a catalyst affect the rate?
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It interacts with the reactants to create an alternative pathway for product production.
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 What is the Haber Process?
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the synthesis of ammonia facilitated by a solid phase catalyst.

 

-diatomic gases bind to the surface

-bonds weakened

-newly formed NH3 leaves the solid surface

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Dynamic equilibrium
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the rate of the forward process in a reversible reaction is exactly balanced by the rate of the reverse process.

 

Ex: sugar in H20, it may look like nothing more is dissolving, but actually some of sugar continues to be dissolved and at the same rate solid sugar molecules are being formed.

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what is left out in the equilibrium constant expression?

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Pure liquids and solids are not shown.  Only gases and substances are shown.
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what does the equilbrium constant tell us?
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the extent to which reactants have converted to products.

 

-addition of products or reactants does not affect the value of the equilibrium constant.

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Le chateleir principle
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if a stress is placed on a system at equilibrium, the system will respond by altering the equilibrium composition in such a way as to minimize the stress.
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How does the arrhenius theory describe acids and bases?
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a base dissociates to form H+

an acid dissociates to form OH-

 

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How does Bronsted-Lowry theory describe acids and bases?
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an acid is a proton(H+) donor.

a base is a proton(H+) acceptor.

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Amphiprotic
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a substance possesing both acid and base properties.

 

water can act as an acid or base.

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What solvent is most commonly used for acids and bases?
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water
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Decribe strength as related to acids and bases.
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strength is a measure of degree of dissociation of an acid or base in solution, independant of concentration.

 

-acids and bases are classified as strong when the reaction with water is 100% complete. 

 

Acids with the greatest proton donating capability (strongest acids) have the weakest conjugate bases.

Good proton acceptors(strong bases) have weak conjugate acids.

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Ionization and auto ionization.
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dissociation of acids and bases is called ionization.

-water goes through autoionization (self-ionization)

 

-water is a weak electrolyte and a poor conductor of electricity.

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Why do acids burn skin?
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because of their exothermic reaction with water present on and in the skin.

 

-bases react with proteins, affecting the skin and eyes.

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Ion product for water, Kw
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this refers to the product of hydronium and hydroxide ion concentration in pure water.

 

-the ion product is a temperature dependant quantity.

-It equals 1.0 x 10-14 at 25 C

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pH scale

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gauges the hydronium ion concentration and reflects degree of acidity or basicity of a soln.

 

-if add an acid (H3O), (OH decreases)

-if add a base (OH), (H3O decreases)

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Neutralization
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the reaction of an acid with a base to produce a salt and water.

 

-when writing a net, balanced equation remove spectator ions(dont change)

 

-the analytical techniqu to determine the concentration of an acid or base is titration

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Polyprotic substances
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donates or accepts more than one H+ ion per each formucla unit.

 

Ex: H2SO4

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Buffer solution
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a solution which resists large changes in pH when either acids or bases are added.

- they establish equilibrium between a weak acid and its conj base or a weak base and its conj acid.

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What happens when OH- is added to buffer solution?
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OH reacts with H3O to produce water, acid dissociates to replace H3O.

 

therefore shift to right occurs.

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What happens when acid is added to a buffer solution?
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-shift to the left occurs
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Buffer capacity
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the amount of strong acid or strong base that a buffer can neutralize without significantly changing the pH.

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Oxidation
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-loss of electrons

 

-loss of hydrogen atoms

 

-gain of oxygen atoms

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Reduction
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-gain of electrons

 

-gain of hydrogen

 

-loss of oxygen

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Oxidizing agent
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-is reduced

 

-gains electrons

 

-causes oxidation

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Reducing agent
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-is oxidized

 

-loses electrons

 

 -causes reduction

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corrosion
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the deterioration of metals caused by an oxidation-reduction process
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applications of red-ox reactions
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Corrosion, combustion of fossil fuels, and bleaching.

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Biological processes involving redox rxns.
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Respiration, Metabolism

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Voltaic cells
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electrochemical cell that converts stored chemical energy into electrical energy.

 

Ex:batteries

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anode
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the electrode at which oxidation occurs in a voltaic cell.
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cathode
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electrode at which reduction occurs.
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Electrolysis
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use electrical energy to cause nonspontaneous oxidation-reduction reactions to occur.

 

-they are the reverse of voltaic cells.

 

Ex: rechargable battery

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What type of nuclei have ratioactive decay?
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Olny unstable nuclei undergo change and produce radioactivity
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Isotope
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refers to any atoms that have the same atomic number but different mass number.
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Nuclide
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refers to any atom characterized by an atomic number and a mass number.
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Alpha particles
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-2 protons, 2neutrons

-same as He nucleus

-slow, stopped by small barriers(travels 10% of speed of light)

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Beta particles
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-fast moving electron(travels at about 90% of speed of light)

 

-emitted from the nucleus as a neutron converted to a proton.

 

 

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Gamma rays
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pure energy (electromagnetic radiation)

-highly energetic

 

most penetrating

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Ioninzing radiation
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produces a trail of ions throughout the material that it penetrates.

 

alpha<beta<gammarays

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Positron Emission
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-same mass as beta particle, but carries positive charge.

 

-produced by the conversion of a proton to a neutron in the nucleus of the isotope.

-unlike beta, it has the same mass number, but the atomic number has decreased by one.

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binding energy
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the energy that holds the protons,neutrons, and other particles together in the nucleus.

 

-in radioisotopes binding energy is large

 

when isotopes decay(become more stable) binding energy is released.

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half life (t1/2)
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is the time required for one half of a given quantity of a substance to undergo change.

 

-isotopes with short half-lives decay rapidly;they are very unstable.

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radiocarbon dating

 

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the ratio of carbon-14 to carbon-12 stays constant during its lifetime.

 

-when living system dies, it quits taking in the carbon-14

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How old can the artifact be to be able to use carbon-14 dating?

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Less than 50,000 years
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Fission(splitting)
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occurs when a heavy nuclear particle is split into smaller nuclei by a smaller nuclear particle.

-produces large amts of energy

 

-is self perpetuating

 

-can be used to generate steam

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Nuclear Fusion
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combination of two small nuclei to form a larger nucleus.

 

-large amts of energy released

-Ex: sun

 

-no plant exists

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Breeder reactor

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fission reactor that manufactures its own fuel

 

-nuclear energy(nuclear reactor)--heat energy(steam)--mechanical energy(turbine)--electrical energy(electricity)

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Distance from radio active source

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radiation intensity varies inversely with the square of the distance from the source.

 

-doubling the distance from source decreases the intensity by a factor of 4.

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