Inorganic and physical chemistry - part 3

Question 1

what is the standard enthalpy of formation?

Answer 1

enthalpy change when one mole of a substance is formed from its elements in their standard states

Question 2

state the three standard conditions

Answer 2

• per mole
• one atmosphere
• specified temperature (usually 298K)

Question 3

what is a standard state?

Answer 3

state element is most commonly observed in at standard conditions

Question 4

what value in degrees Celsius is absolute zero?

Answer 4

-273

Question 5

what is entropy a measure of?

Answer 5

measure of the degree of disorder in a system

Question 6

what is the third law of thermodynamics?

Answer 6

at absolute zero, a crystal lattice has a perfect order and zero entropy

Question 7

what happens to the entropy value as the temperature increases?

Answer 7

entropy increases

Question 8

what has a greater entropy, a solid or a gas?

Answer 8

a gas

Question 9

when is a process spontaneous?

Answer 9

when it can take place without being driven by an external force

Question 10

why can a process be spontaneous?

Answer 10

• entropy increase is so large

- counterbalances the unfavourable enthalpy change

Question 11

as heat energy is released by a reaction system, what happens to the entropy of the surroundings?

Answer 11

entropy increases

Question 12

as heat energy is absorbed by a reaction system, what happens to the entropy of the surroundings?

Answer 12

entropy decreases

Question 13

when is a reaction feasible

Answer 13

reaction tends towards the products side rather than reactants

Question 14

what is the second law of thermodynamics?

Answer 14

for a reaction to be feasible, the total entropy change for a reaction system and its surroundings must be positive

Question 15

what must be negative for a reaction to be feasible?

Answer 15

free energy

Question 16

what is happening to the reaction when (delta)G=0

Answer 16

reaction is at equilibrium

Question 17

when is the free energy of the system at its minimum value?

Answer 17

at equilibrium

Question 18

if (delta)G is large and negative, on which side of the reaction will the equilibrium lie?

Answer 18

lies on products

Question 19

if (delta)G is large and positive, on which side of the reaction will the equilibrium lie?

Answer 19

lies on reactants

Question 20

what is zero order?

Answer 20

doubling the concentration has no effect on the rate

Question 21

for a zero order reaction, what is the units of k?

Answer 21

mol l^-1 s^-1

Question 22

for a first order reaction, what is the units of k?

Answer 22

s^-1

Question 23

for a second order reaction, what is the units of k?

Answer 23

l mol^-1 s^-1

Question 24

for a third order reaction, what is the units of k?

Answer 24

l^2 mol^-2 s^-1

Question 25

what is a first order?

Answer 25

doubling the concentration, doubles the rate

Question 26

what is second order?

Answer 26

doubling the concentration, quadruples the rate

Question 27

which step is the rate determining step (rate law)?

Answer 27

slow step

Question 28

what does the rate law show?

Answer 28

shows information about possible reaction mechanisms

Question 29

what is a reaction mechanism a description of?

Answer 29

description of the steps involved in the reaction going from reactants to products