Physical chemistry and transition elements

Question 1

What is the equation of rate constant ?

Answer 1

Kc = Conc products / Conc reactants

Question 2

What does the value of Kc indicate ?

Answer 2

Kc = 1, equillibrium is exactly in the middle

Kc > 1, Equillibrium lies towards the products

Kc < 1, Equillibrium lies towards reactants

Question 3

What are the different order of reactions ?

Answer 3

0 order
1st order
2nd order

Question 4

What are the features of a 0 order reactant ?

Answer 4

• Conc of reactants has no effect on the rate of reaction
• Concentration does not influence the rate of reaction

Question 5

What are the features of a 1st order reactant ?

Answer 5

[A]
- Concentration of the reactant is directly proportional to the rate

Question 6

What are the features of a 2nd order reactant ?

Answer 6

[A]^2
- Rate is affeted to the power of conc.

Question 7

How can order of reactants be determined ?

Answer 7

Experimentally

Question 8

What is the concentration time graph for a zero order reactant ?
How can you find the rate constant from this graph ?

Answer 8

Rate constant = gradient
Straight line with a negative gradient

Question 9

What is the concentration time graph for a 1st order reaction ?
How can you find the rate constant from this graph ?

Answer 9

• Downwards curve with CONSTANT HALF LIVES
• Rate constant = ln(2) / t0.5

Question 10

What is the concentration time graph for a 2nd order reactant ?

Answer 10

• No constant half lives

Question 11

How do you plot a rate concentration graph ?

Answer 11

• Plotted from initial rate at different concentrations

Question 12

What is the shape of a 0 order rate concentration graph ?
How can you find the rate constant ?

Answer 12

• Y intercept is the rate constant

Question 13

What is the shape of a 1st order rate concentration graph ?
How can you find the rate constant ?

Answer 13

• Gradient is the rate constant

Question 14

What is the shape of a 2nd order rate concentration graph ?
How can you find the rate constant ?

Answer 14

• K is determined by plotting rate against concentration^2

Question 15

What is initial rate ?

Answer 15

• Instant rate at the start of a reaction (when T=0)

Question 16

How can you measure initial rate ?

Answer 16

1/t

Question 17

What is the rate determining step ?

Answer 17

• Slowest step in the chemical reaction

Question 18

Why do reactions usually have two steps ?

Answer 18

It is unlikely that a chemical reaction will occur in one step as it is unlikely that more than 2 molecules will collide with the correct orientation and sufficient energy

Question 19

What does the extended form of the Arrhenius equation link to ?

Answer 19