Lab M

Question 1

Activated Complex/Transition State

Answer 1

the state at which molecular energy is high enough for electron orbitals to overlap and thus a reaction to occur

Question 2

Activation Energy

Answer 2

the minimum amount of energy required to reach the transition state/create an activate complex or have a reaction occur

Question 3

Draw an exothermic graph of potential energy vs reaction pathway

Question 4

Draw an endothermic graph of potential energy vs reaction pathway

Question 5

How does changing activation energy affect K

Answer 5

increasing activation energy decreases K
decreasing activation energy increases K

Question 6

How does changing concentration of reactants affect K

Answer 6

K is constant at a constant temperature

Question 7

How does changing temperature affect K

Answer 7

increasing temperature, increases K
decreasing temperature, decreases K

Question 8

What are the parts of the Arrhenius equation:

K = A(exp(-Ea/(RT)))

Answer 8

A is the number of collisions with the correct orientation
the exponential term is the fraction of collisions with energy greater than the activation energy

Question 9

Ln linearized form of Arrhenius equation:

K = A(exp(-Ea/(RT)))

Answer 9

lnK = (-Ea/R) * (1/T) + lnA

Question 10

Log linearized form of Arrhenius equation:

K = A(exp(-Ea/(RT)))

Answer 10

logK = (-Ea/2.303R) * (1/T) + logA

Question 11

Catalyst

Answer 11

• provides an alternative pathway for a reaction
• speeds up reaction by lowering activation energy

Question 12

How do catalysts affect the amount of product formed

Answer 12

Catalysts do not change amount of product formed

Question 13

Lab M, reaction

Answer 13

2I ^1- + S208 ^2- = I2 + SO4 ^2-

Iodide + Peroxydisulfate = Iodine + Sulfate

While thiosulfate is present
I2 + 2S203^2- = I-

Question 14

Iodine Clock Timeline

Answer 14

• I- and S208 ^ 2- mixed with starch and thiosulfate
• solution produces I2
• thiosulfate converts all I2 back to I-
• thiosulfate is used up
• I2 is formed
• I2 reacts with I- to form triodide (I3 ^-1)
• I3^ -1 reacts with starch, turning solution deep blue
• time is stopped
• I2 continues to be formed

Question 15

Thiosulfate’s role

Answer 15

converts I2 back into I-

Question 16

Δt (2 points)

Answer 16

• time to react and use up the small amount of thiosulfate added to mixture
• [I2] formed during a certain time interval is always constant

Question 17

how to calculate Δ[I2]

Answer 17

1/2 * S2O8 ^2-

Question 18

How does changing the temperature affect Δt

Answer 18

Increasing the temp. increases the rate of reaction and decreases Δt

Decreasing the temp. decreases the rate of reaction and increases Δt

Question 19

why is EDTA added to the mixture

Answer 19

EDTA prevents trace metals from catalyzing reaction

Question 20

Lab M Process (7 steps) (Hint: Thiosulfate

Answer 20

1. Peroxydisulfate dissolved in water
2. Iodide dissolved in water
3. In a beaker, combine iodide, EDTA, starch, and thiosulfate
4. peroxydisulfate added to beaker
5. solution turns deep blue
6. experiment repeated at different temperatures
7. experiment repeated without EDTA

Question 21

In lab M when you dissolve peroxydisulate in water What colour should the S2O8 ^2- aqueous solution be

Answer 21

clear and colourless

Question 22

When you dissolve iodide in water in experiment M, what colour should the aqueous solution be

Answer 22

clear and colourless - faint yellow