Unit 3: Heat, Energy, and Reactions

Question 1

Heat

Answer 1

(q) energy that transfers from one object to another because of a temperature difference between the objects

Question 2

Temperature

Answer 2

a measure of the average kinetic energy of particles in matter; temperature determines the direction of heat transfer

Question 3

Endothermic

Answer 3

a process that absorbs heat from the surroundings

Question 4

Exothermic

Answer 4

a process that releases heat to its surroundings

Question 5

Specific heat

Answer 5

the amount of heat needed to increase the temperature of 1 g of a substance 1*C; also called specific heat capacity

Question 6

Enthalpy

Answer 6

(H) the heat content of a system at constant pressure

Question 7

Heat of formation

Answer 7

(ΔHf^0) the change in enthalpy that accompanies the formation of 1 mole of a compound from its elements with all substances in their standard states at 25*C

Question 8

Le Chatelier’s Principle

Answer 8

when a stress is applied to a system in dynamic equilibrium, the system changes is a way that relieves the stress

Question 9

Transition state

Answer 9

a term sometimes used to refer to the activated complex

Question 10

Activation energy

Answer 10

the minimum energy colliding particles must have in order to react

Question 11

catalyst

Answer 11

a substance that increases the rate of reaction by lowering the activation-energy barrier; the catalyst is not used up in the reaction

Question 12

Entropy

Answer 12

(S) a measure of the disorder of a system; systems tend to go from a state of order (low entropy) to a state of maximum disorder (high entropy)

Question 13

Spontaneous Reaction

Answer 13

a reaction that favors the formation of products at the specified conditions; spontaneity depends on enthalpy and entropy changes

Question 14

Non-spontaneous reaction

Answer 14

a reaction that does not favor the formation of products at the specified conditions

Question 15

1 Calorie

Answer 15

= 1 kilocalorie = 1000 calories

Question 16

Specific heat formula (C)

Answer 16

C = q/(m * ΔT)
q= heat in J or cal
m= mass in grams
ΔT= change in temp, in *C

Question 17

Convert calorie to joules

Answer 17

1 cal = 4.184 J

Question 18

Gibbs free-energy change

Answer 18

ΔG = ΔH – TΔS

Question 19

q = m * ΔH Vaporization

Answer 19

.

Question 20

rate = k[A]a[B]b

Answer 20

.

Question 21

q = m * ΔH fusion

Answer 21

.

Question 22

Equilibrium constant

Answer 22

K(eq) = ([C]^c * [D]^d) / ([A]^a * [B]^b)

Question 23

What does the heat capacity of an object partially depend upon?

Answer 23

Mass and chemical composition

Question 24

Which of the following phases of H2O is arranged in an increasing order of entropy?

Answer 24

Ice, liquid water, and steam

Question 25

Describe how a container that has an endothermic reaction occurring would feel compared to a container with an exothermic reaction occurring.

Answer 25

An ENDOthermic reaction feels cold

An EXOthermic reaction feels hot

Question 26

List three factors that will increase the reaction rate in a chemical reaction.

Answer 26

• use of a catalyst
• decrease particle size
• increase concentration of reactants

Question 27

What is meant when a reaction is referred to as being reversible? Compare the reactant amounts to the product amounts in a reversible reaction.

Answer 27

The conversion of reactants to products and products to reactants occur at the same rate, the concentration of products and reactants are equivalent

Question 28

What is the difference between temperature and heat?

Answer 28

Temp measures the amount of energy stored in a substance, while heat is a measure of the energy transferred from one substance to another

Question 29

Calculate the energy needed to produce 10 moles of Cl2O7 using the following balanced equation. 2Cl2(g) + 7O2(g) + 100 kCal  2Cl2O7(g)

Answer 29

.

Question 30

What causes a reaction to be spontaneous? Provide one example.

Answer 30

.