CHEM 1125Q: EXAM 1
85 Cards in this Set
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System vs. surroundings
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a system is part of the universe that is of specific interest
surroundings constitute the rest of the universe outside of the system
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thermochemistry
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the study of heat (the transfer of thermal energy) in chemical reactions
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Heat transferred from the system to the surroundings is called
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an exothermic reaction
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Heat transferred from the surroundings to the system
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An endothermic process
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Thermodynamics
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the study of the interconversion of hear and other kinds of energy
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3 types of thermodynamic systems (name and define)
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open: exchange mass and energy with surroundings
closed: allows the transfer of energy but not mass with surroundings
isolated: does not exchange either mass or energy with its surroundings
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State functions (define and types)
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Properties that are determined by the state of the system, regardless of how that condition was achieved. Ex. energy, pressure, volume and temperature
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First law of thermodynamics (equation)
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ΔUsys + ΔUsurr = 0
ΔU is the change in the internal energy
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Overall change int he systems internal energy (equation)
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ΔU = q + w
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define...
+q, -q, +w, -w
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+q is endothermic process
-q is exothermic process
+w is for work done on the system
-w is for work done by the system
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equation of enthalpy
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H = U + PV
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Enthalpy of reaction (define and equation)
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The difference bewteen the enthalpies of the products and that of the reactants
ΔH = H(products) – H(reactants)
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Is enthalpy an intensive or extensive property?
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Extensive, meaning it's dependent on the amount of matter involved
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Calorimetry
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the measurement of heat changes
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specific heat
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(s) the amount of heat required to raise the temperature of 1 g of the substance by 1 C
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heat capacity
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(c) is the amount of heat required to raise the temperature of an object by 1 C
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bomb calorimeters are ____ ____ calorimeters and are used to determine....
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constant volume, and used to determine the heat of combustion
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Hess's Law
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States that the change in enthalpy for a stepwise process is the sum of the enthalpy changes for each of the steps
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Born-Haber cycle
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a cycle that relates the lattice energy of an ionic compound to qualities that can be measured
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Characteristics of Gas
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-gas can assume the shape and volume of the container
-gas can be easily compressed
-densities of gases are much smaller than those of liquids and solids and are highly variable depending on temperature and pressure
-gases orm homogeneous mixtures with one another in ant proportion
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4 basic assumptions of the kinetic molecular theory
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1. gas is composed of particles that are separated by large distances
2. gas molecules are constantly in random motion
3. gas molecules do no exert attractive or repulsive forces on one another
4. the average kinetic energy of a gas molecule in a sample is proportional to the absolute …
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What can cause an increase in the frequency of collisions of gas molecules?
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Decreasing volumes and increasing pressure
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Root-mean-square speed (Urms)
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the speed of a molecules with the average kinetic energy in a gas sample.
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Urms is directly proportional to ____ and inversely proportional to ___.
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Temperature;
square root of molar mass
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diffusion
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the mixing of gases as the result of random motion and frequent collisions
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effusion
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the escape of gas molecules from a container to a region of vaccum
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Graham's law states
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that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molar mass
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pressure
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the force applied per unit area
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batometer
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an instrument that is used to measure atmospheric pressure
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Standard atmospheric pressure was originally defined as...
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the pressure that would support a column of mercury exactly 760 mm high
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manometer
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a device used to measure pressures other than atmospheric pressure
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Boyle's law states
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that the pressure of a fixed amount of gas at a constant temperature is inversely proportional to the volume of the gas
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Charle's and Gay-Luccac's Law states
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that the volume of a gas maintained at a constant pressure is directly proportional to the absolute temperature of the gas
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How do gases behave when they are placed in a container with another gas?
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They behave as thought they occupy the container alone.
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Daltons Law
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States that the total pressure exerted by a gas mixture is the sum of the partial pressures exerted by each component of the mixture
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Relative amounts of the components in a gas mixture can be specified using...
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mole fractions
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3 things to remember about mole fractions
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1. mole fraction of a mixture component is always less than 1
2. the sum of the mole fractions for all components of a mixture is always 1
3. mole fractions are dimensionless
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The strength of an intermolecular force _____ as we progress from a gas to a liquid to a solid
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increases
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surface tension
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the amount of energy required to stretch or increase the surface area of a liquid by a unit area
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viscosity (define and what causes it)
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a measure of a fluids resistance to flow, higher viscosity, slower flow,
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A higher viscosity leads to....
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A slower flowing liquid
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Vaporization
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When a molecule at the surface of a liquid has enough kinetic energy, it changes into a gas
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dynamic equilibrium
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When the forward process and the reverse process are occurring at the same rate (rate of evaporation equals the rate of condensation)
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Vapor pressure ____ with temperature increase
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Increases
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Clausius-Clapeyron equation
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relates the natural log of vapor pressure and the reciprocal of absolute temperature
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Definition of boiling point
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the temperate at which the vapor pressure equals the external atmospheric pressure
Varies with the external pressure and the magnitude of the intermolecular forces
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Define melting point
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The temperature at which the energies of the individual particles enables them to break free of their fixed positions
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Amorphous solids
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lack a regular three-dimensional arrangement of atoms (i.e. glass)
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Crystalline solid
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possesses rigid and long-range order; its atoms, molecules or ions occupy specific positions
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Coordination number
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the number of atoms surrounding an atom in a crystal lattice, indicates how tightly the atoms are packed together
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Types of cubic cells, in order from least to most atoms
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Primitive, body-centered, face-centered
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Rhodium, a precious metal, crystallizes in a face-centered unit cell (cubic closest packed). It has a density of 12.41 g/cm3. What is the radius of a rhodium atom?
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r=1.35*10^-8 cm
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Ionic crystals are composed of _____ and held together by ____ _____.
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charged ions; Coulombic attraction
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atoms held together in an extensive, 3-D network entirely by covalent bonds
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Covalent crystals
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Atoms whose lattice points are occupied by other molecules, the attractive forces between them are van der Waal and or hydrogen bonding
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Molecular crystals
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Polonium, a radioactive metal, is one of the few examples of simple cubic crystal symmetry. It has a density of 9.3 g/cm3 and an atomic radius of 167 pm. Its molar mass is 209 g/mol. Use these data to calculate Avogadro’s number.
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6.03*10^23 atoms/mol
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freezing
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liquid to solid
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Evaporation
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Liquid to gas
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Fusion
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Solid to liquid
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Condensation
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Gas to liquid
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Sublimation
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Solid to gas
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Deposition
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gas to solid
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Define boiling point
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The temperature at which its vapor pressure equals the external atmospheric pressure
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Mole heat of vaporization
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The amount of heat needed to vaporize a mole os substance at its boiling point
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critical temperature
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the temperature above which its gas cannot be liquified
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crystal pressure
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the minimum pressure that must be applied to liquefy a substance at its critical temperature
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molar heat of fusion
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the energy required to melt 1 mole of a solid
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Molar enthalpy of sublimation (define and equation)
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the energy requires to sublime 1 mole of a solid
ΔHsub = ΔHfus + ΔHvap
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Consider a process where 15.0 g of steam at 100 ⁰C cools to water at 37.0 ⁰C. How much heat is released in the process?
The specific heat of water is 4.184 J/g ⁰C and that of steam is 1.998 J/g ⁰C
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38 kJ
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Ethyl alcohol has a heat of vaporization of 30.72 kJ/mol and a normal boiling point of 78.4 ⁰C. What is its vapor pressure at 15.0 ⁰C?
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e^2.314
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What is the change in internal energy for a system that absorbs 255 kJ of energy from its surroundings and does 137 kJ of work?
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118 kJ
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Determine the work done (in joules) when a sample of gas expands from 552 mL to 915 mL at constant temperature
1. against a constant pressure of 1.25 atm,
2. against a constant pressure of 1.00 atm, and
3. against a vacuum
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1 L∙atm = 101.3 J
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-45.96 J
-36.8 J
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Given the thermochemical equation for photosynthesis,
6H2O(l) + 6CO2(g) → C6H12O6(s) + 6O2(g)
ΔH = +2803 kJ/mol
calculate the energy required to produce 25.0 g of C6H12O6. This energy comes largely from the sun (so called solar energy).
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389 kJ
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A metal pellet with a mass of 100.0 g, originally at 88.4°C, is dropped into 125 g of water originally at 25.1°C. The final temperature of both pellet and the water is 31.3°C. Calculate the specific heat s (in J/g°C) of the metal. Assume the calorimeter absorbs no heat.
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0.568 J/g-C
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A 0.1375-g sample of solid magnesium is burned in a constant-volume bomb calorimeter that has a heat capacity of 3024 J/°C. The temperature ieases by 1.126°C. Calculate the heat given off by the burning Mg, in kJ/g and in kJ/mol..
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-602 kJ/mol
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Determine the molar mass and identity of a diatomic gas that moves 4.67 times as fast as CO2.
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MM=2.02, h2 gas
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Calculate the pressure exerted by a column of water 1.50 m high. Express the pressure in atmospheres and in Pa. The density of water is 1.00 g/cm3.
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1.47 Pa, 0.145 atm
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A 65.0 L weather balloon filled with helium is released where the temperature is 21.50°C and the air pressure is 755.2 mmHg. What will the volume of the balloon be when it has risen to an altitude where the temperature is -65.15°C and the air pressure is 325.5 mmHg?
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106L
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A sample of 3.50 moles of NH3 gas occupies 5.20 L at 47°C. Calculate the pressure of the gas (in atm) using (a) the ideal gas equation and (b) the van der Waals equation.
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Ideal: 17.7 atm
Van der Walls: 16.2 atm
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A 10.00-L vessel contains 0.500 mole of N2 gas and 0.500 mole of He gas at 25.0°C. Determine the partial pressure of each component and the total pressure in the vessel.
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2.44 atm
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A tank contains 52.5 g of oxygen gas and 65.1 g of carbon dioxide gas at 27.0 °C. The total pressure in the tank is 9.25 atm. What are the partial pressures of the two gases in the tank?
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4.38
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Crystal with hard toughness, high melting point, poor conductivity as a solid, good conductivity as an aqueous solution. Example
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Ionic crystal (NaCl)
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Crystal with hard toughness, high melting point, poor conductivity as a solid and aqueous solution. Example
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Network covalent (carbon, SiO2)
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Crystal with soft toughness, low melting point, poor conductivity as both a solid and aqueous solution. Example
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Molecular crystal (CO2, H2O)
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Crystal with variable toughness, variable melting point, poor conductivity as a solid, and no aqueous form. Example
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Metallic crystal (metals)
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CHEM 1125Q: EXAM 1