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120 Cards in this Set
- Front
- Back
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1.
Which of the following is a measure of the average kinetic energy of the particles in a sample of matter? |
d.
temperature |
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2.
Which of the following best describes temperature? |
b.
a measure of the average kinetic energy of the particles in a sample of matter |
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3.
In what units is temperature measured? |
c.
both degrees Celsius and kelvins |
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4.
How is a Celsius temperature reading converted to a Kelvin temperature reading? |
c.
by dividing by 273.15 |
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5.
The greater the kinetic energy of the particles in a sample of matter, |
a.
the higher the temperature is. |
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6.
The energy transferred between samples of matter because of a difference in their temperatures is called |
a.
heat. |
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7.
Which of the following best describes heat? |
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the energy transferred between samples of matter because of a difference in their temperatures |
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What units are used to measure heat? |
c.
joules or kilojoules |
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9.
What is the heat required to raise the temperature of 1 g of a substance by 1 ºC or 1 K? |
a.
specific heat |
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10.
What units are used to measure specific heat? a. J/g·ºC c. cal/g·ºC b. J/g·K d. All of the above |
d
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11.
Which expression defines specific heat? |
heat/massxtemperature change
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A 4.0 g sample of iron was heated from 0ºC to 20.ºC. It absorbed 35.2 J of energy as heat.
What is the specific heat of this piece of iron? |
d.
0.44 J/g·ºC |
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13.
How much energy does a copper sample absorb as heat if its specific heat is 0.384 J/g·ºC, its mass is 8.00 g, and it is heated from 10.0ºC to 40.0ºC? a. 0.0016 J/g·ºC c. 92.2 J b. 0.0016 J d. 92.2 J/g·ºC |
c.
92.2 J |
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4.
Find the specific heat of a material if a 6-g sample absorbs 50 J when it is heated from 30ºC to 50ºC. |
d.
0.4 J/g·ºC |
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15.
How much energy is absorbed as heat by 20. g of gold when it is heated from 25ºC to 35ºC? The specific heat of gold is 0.13 J/g·ºC. |
a.
26 J |
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16.
A 5.0 g sample of silver is heated from 0ºC to 35ºC and absorbs 42 J of energy as heat. What is the specific heat of silver? |
b.
0.24 J/g·ºC |
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17.
Enthalpy change is the |
c.
temperature change of a system at constant pressure. |
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18.
The quantity of energy released or absorbed as heat during a chemical reaction is called the |
b.
heat of reaction |
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19.
The Greek letter D stands for |
d.
"change in." |
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20.
What is the difference between the enthalpies of the products and the reactants? |
c.
DH |
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21.
What is the energy released or absorbed as heat when one mole of a compound is produced by combination of its elements? |
a.
heat of formation |
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22.
Compounds whose heats of formation are highly negative |
d.
are very stable. |
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23.
DH = _______ . |
c.
Hproducts – Hreactants |
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Suppose that a chemical equation can be written as the sum of two other chemical equations. If two reactions have DH values of –658 kJ and +458 kJ, what is DH for the reaction that is their sum?
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–200 kJ
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Suppose reaction A has a DH of –200 kJ and reaction B has a DH of –100 kJ. If reaction C can be written as the sum of reaction A forward and reaction B reversed, what is DH for reaction C?
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–100 kJ
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The heat of formation of compound X is –612 kJ/mol, and the sole product of its combustion has a heat of formation of –671 kJ/mol. What is the heat of combustion of compound X?
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a.
–59 kJ/mol |
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What is the heat of combustion of 1 mol of sulfur to form SO2?
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–296.8 kJ/mol
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What is the heat of formation of hexane, C6H14?
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–198.4 kJ/mol
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What is the heat of formation of ethane, C2H6?
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–83.7 kJ/mol
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What is the value of DG at 300 K for a reaction in which DH = –150 kJ/mol and DS = +2.00 kJ/mol·K?
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–750 kJ/mol
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The driving force of a reaction depends mostly on the change in
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enthalpy.
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A system that changes spontaneously without an enthalpy change
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becomes more disordered.
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Spontaneous reactions are driven by
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decreasing enthalpy and increasing entropy.
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Compared with a single gas, a mixture of gases is
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more disordered.
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Why do gases naturally mix with each other when combined?
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The entropy change is favorable.
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Which of the following is a measure of the disorder in a system?
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entropy
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If a process increases entropy, the process
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is likely to be spontaneous.
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What is the symbol for entropy?
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S
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What drives spontaneous reactions?
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decreasing enthalpy and increasing entropy
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What does DS stand for?
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entropy change
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Which of the following substances has the highest entropy?
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steam
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Which of the following systems has the lowest entropy?
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a container of frozen water
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Entropy decreases when
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temperature decreases.
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Which of the following has the highest entropy when produced in a reaction?
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gas
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The driving force of a reaction is the change in
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free energy.
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What is the symbol for free-energy change?
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DG
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Free-energy change depends on
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temperature and changes of entropy and enthalpy.
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Which expression defines the change in free energy?
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DH – TDS
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In DG calculations, temperature is expressed in
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kelvins
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A reaction is spontaneous if DG is
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negative
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Spontaneity is favored by large positive values of
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DS
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What quantity predicts whether a reaction is spontaneous?
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free energy
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Entropy plays a larger role in determining the free energy of reactions that take place at
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high temperatures.
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Which depends only on the initial and final states of a reaction, rather than on the intermediate processes?
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both DH and DS
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The equation H2(g) + I2(g) ® 2HI(g) is a(n)
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overall reaction.
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What is the sequence of steps in a reaction called?
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reaction mechanism
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Examining a chemical system before and after reaction reveals the
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net chemical change.
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Most steps in a reaction mechanism
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are simple.
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What is the overall equation for the formation of hydrogen iodide from its elements?
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H2(g) + I2(g) 2HI(g)
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What is the initial step in the formation of hydrogen iodide from its elements?
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I2(g) 2I(g)
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Which of the following is NOT a step in the formation of hydrogen iodide from its elements?
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H2(g) 2H(g)
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How many steps are in the pathway when hydrogen iodide forms from its elements?
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two or three
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To react, gas particles must
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collide
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To be effective, a collision requires
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sufficient energy and a favorable orientation.
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If colliding molecules have an orientation that favors reaction, they have
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the correct angles and distances between atoms.
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What attempts to explain chemical reactions and physical interactions of molecules?
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collision theory
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Raising the temperature of reactants in a system
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increases the average kinetic energy of the molecules.
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Raising the temperature of reactants in a system
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increases the average molecular motion.
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Raising the temperature of gas particles
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increases collision energy but does not increase favorability of orientation.
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If a collision between molecules is very gentle, the molecules are
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more likely to rebound without reacting.
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The minimum energy required for an effective collision is called
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activation energy.
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A short-lived structure formed during a collision is a(n)
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activated complex.
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How does the energy of the activated complex compare with the energies of reactants and products?
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It is higher than the energy of both reactants and products.
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Activation energy is
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the energy required to form the activated complex.
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The bonding of the activated complex is characteristic of
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both reactants and products.
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In an energy-profile graph, the activated complex is represented at the
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top of the curve.
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An activated complex
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may either separate into the products or re-form the reactants.
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In a diagram of an activated complex, broken lines represent
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partial bonds.
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What takes place in an activated complex?
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Some bonds form and other bonds break.
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What is the energy needed to lift reactants from the energy trough?
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activation energy
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Which statement correctly describes the energy changes that occur when bonds form and when bonds break?
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Breaking bonds is endothermic, and forming bonds is exothermic.
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Which of the following is true in an endothermic reaction?
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energy of reactants < energy of products < activation energy
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Which of the following is true in an exothermic reaction?
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energy of products < energy of reactants < activation energy
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What branch of chemistry studies reaction rates?
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chemical kinetics
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What branch of chemistry studies reaction mechanisms?
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chemical kinetics
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The usual conditions for reaction are not always necessary for
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decomposition reactions.
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Chemical kinetics studies
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the factors that affect the rate of reaction and the mathematical expressions for the rate of reaction.
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For most reactions, particles must
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collide in the proper orientation.
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Reaction rate depends upon
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both collision frequency and efficiency.
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Which of the following affects reaction rate?
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a.
the nature of reactants c. temperature b. surface area of reactants d. All of the above |
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Which substance naturally combines most rapidly with oxygen?
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sodium
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Which of the following burns most slowly?
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a large lump of coal
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If the surface area of reactants is larger,
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the reaction rate is generally higher.
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In heterogeneous reactions, the reactants
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are in different phases.
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If the concentration of reactants is higher,
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the reaction rate is generally higher.
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If the temperature of the reactants is lower,
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the reaction rate is generally lower.
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A sample of a substance burns more rapidly in pure oxygen than in air. Which factor is most responsible for this high rate of reaction?
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concentration of the substance
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Changing the temperature affects the rate of reaction because it affects
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the frequency of collision and the number of effective collisions.
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Which process is used to speed up chemical reactions?
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catalysis
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Which term describes a catalyst in the same phase as the reactants and products?
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homogenous
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Adsorption of reactants on the surface of a metal catalyst changes the reaction rate by affecting the
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concentration of the reactants.
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A substance that slows down chemical processes is called a(n)
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inhibitor.
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Catalysts generally affect chemical reactions by
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providing an alternate pathway with a lower activation energy.
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How is a heterogeneous catalyst different from the reactants in a chemical reaction?
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The phase of the catalyst is different.
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In a net equation, catalysts
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are not shown.
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A rate law relates
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reaction rate and concentrations of reactants.
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The letter k in a rate law stands for
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a proportionality constant.
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The letter R in a rate law stands for
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reaction rate.
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The value of k in a rate law
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varies with temperature.
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Rate laws are determined by
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experiment
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If doubling the concentration of a reactant doubles the rate of the reaction, the concentration of the reactant appears in the rate law with a(n)
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exponent of 1.
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If doubling the concentration of a reactant quadruples the rate of the reaction, the concentration of the reactant appears in the rate law with a(n)
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exponent of 2.
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The rate law for a reaction generally depends most directly on the
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rate-determining step.
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The rate for a reaction between reactants X, Y, and Z is directly proportional to [X] and to [Y], and proportional to the square of [Z]. What is the rate law for this reaction?
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R = k[X][Y][Z]2
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The rate for a reaction between reactants L, M, and N is proportional to the cube of [L] and the square of [M]. What is the rate law for this reaction?
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R = k[L]3[M]2
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Explain the enthalpy change for a chemical reaction in terms of the enthalpies of its products and reactants.
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The enthalpy change for a reaction equals the total enthalpy of the products minus the total enthalpy of the reactants.
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How is a change in free energy related to changes in enthalpy and entropy?
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The change in free energy is the difference between the change in enthalpy and the product of the Kelvin temperature and the entropy change. This relationship can be stated mathematically as DG = DH – TDS.
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How does temperature affect the free energy of a reaction?
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The formula DG = DH – TDS shows that part of the energy change of a reaction is proportional to the temperature. Therefore, at higher temperatures, the contribution of the entropy change is more important in determining the free energy. At lower temperatures, the enthalpy change has more influence on the free energy.
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How does the free-energy equation predict the progress of a chemical reaction?
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The equation DG = DH – TDS shows that the free energy of a reaction depends on the enthalpy change, the entropy change, and the temperature of a reaction. If DG is negative, the change is spontaneous. If DG is positive, the change will not occur spontaneously. If DG is zero, neither the forward nor the reverse reaction is favored, so the result is a mixture of reactants and products.
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Explain in terms of particles why some spontaneous exothermic and endothermic reactions have no apparent activation energy.
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The particles of all substances have an average kinetic energy that depends on the temperature of the substance. Some particles have higher than average kinetic energies, and some have lower than average kinetic energies. The kinetic energy of some particles is large enough to form the activated complex. These particles can react. Then, if the reaction is exothermic, the energy released can activate other particles.
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