Section 6.2- Heat in Chemical Reactions

Question 1

“to warm in”
defined as the internal energy plus the product of the pressure and volume

Answer 1

enthalpy

Question 2

equation for enthalpy

Answer 2

H = E + PV

Question 3

the total enthalpy of a system ___________ be measured

Answer 3

CANNOT

Question 4

equation for the change in enthalpy

Answer 4

delta H = delta E + delta (PV)

Question 5

since most chemical reactions in the laboratory occur in vessels open to the atmosphere (at constant pressure), the change in enthalpy for these reactions is

Answer 5

delta H = delta E + P delta V

Question 6

type of reaction in which some chemical reactions cause energy to be absorbed into the reacting substances and stored in the chemical bonds of the products

Answer 6

endothermic reaction

Question 7

in ______________________ reactions, the products are usually colder than the reactants because energy has been absorbed

Answer 7

endothermic

Question 8

enthalpy is a ______________ function

Answer 8

state

Question 9

a reaction in which some chemical reactions release energy that was stored in the chemical bonds of the reactants

Answer 9

exothermic reaction

Question 10

an _______________________ reaction usually causes the products to become hotter than the reactants because some energy was released as heat, making enthalpy of the products less than reactant

Answer 10

exothermic reaction

Question 11

heat always naturally flows from a _________ object to a _______ object when they are in contact

Answer 11

hot
cold

Question 12

the measurement of heat

Answer 12

calorimetry

Question 13

equation for heat flow

Answer 13

delta T = T (final) - T (initial)

Question 14

the ______________________ of a substance is the heat required to cause a unit rise in the temperature of a unit mass of the substance

Answer 14

specific heat (c)

Question 15

specific heat equation

Answer 15

c = Q/m x delta T

Question 16

the specific heat of water

Answer 16

4.18 J/ (g x C)

Question 17

expecting a negative delta H

Answer 17

exothermic reaction

Question 18

expecting a positive delta H

Answer 18

endothermic reaction

Question 19

amount of energy transferred as heat can be determined by this equation

Answer 19

Q = m x c x deltaT

Question 20

a device for measuring heat flow

Answer 20

calorimeter (heat measure)

Question 21

according to the law of conservation of energy, the sum of the heat lost by a hotter object and the heat gained by a colder object must be ______________; no energy is created or destroyed

Answer 21

ZERO

Question 22

equations for heat loss and gain

Answer 22

Q (lost) + Q (gained) = 0
-Q (lost) = Q gained
- (mcdeltaT) lost= (mcdeltaT) gained

Question 23

the total amount of heat liberated or absorbed between the start of a reaction and its end, where all the products are at the original temperature of the reactants is the

Answer 23

heat of reaction

Question 24

type of equation in which heat is released

Answer 24

thermochemical reaction

Question 25

the reference point chosen for enthalpies is the enthalpy of the uncombined element in it normal state at 1 atm and 298K–

Answer 25

standard state

Question 26

any element in its standard state has an assigned enthalpy of

Answer 26

zero

Question 27

delta H is ____________ if heat is liberated and _________ if heat is absorbed

Answer 27

negative
positive

Question 28

for reactions in which 1 mol of a compound is formed from its elements in their standard states, the enthalpy change is called the

Answer 28

standard enthalpy of formation (delta H*f)