Equilibrium reactions, equilibrium calculations, the properties of water

Question 1

What is the rate of a chemical reaction?

Answer 1

Speed of change in concentration of reactants/products per unit time.

rate (mol L-1 s-1) = change measured / change in time

Question 2

What does the gradient of the tangent to the curve on a conc vs time graph show?

Answer 2

Gives a measure of reaction rate
rate = y2-y1 / x2-x1
rate = change in conc^n / change in time

Question 3

What factors influence a reaction rate?

Answer 3

• conc of reactants
• surface area
• temp
• catalysts

Question 4

What is the relationship between rate and concentration?

Answer 4

rate α conc^n

Question 5

What is K?

Answer 5

equilibrium constant

Question 6

What is k1 and k2?

Answer 6

rate constants

Question 7

What is K equal to?

Answer 7

Rate = k1[A][B] = K2[C][D]
K = [k2] / [k1] = [C][D] / [A][B]

Question 8

What is the total pressure (PT) of a mixture of ideal gases equal to?

Answer 8

PT = PA + PB + PC + PD

Question 9

What is the ideal gas equation?

Answer 9

PV = nRT

Question 10

What is the relationship between the partial pressure and concentration of a gas?

Answer 10

PA α n

Question 11

What is Kc?

Answer 11

molar concentration

Question 12

What is Kp?

Answer 12

partial pressures

Question 13

What are the two main purposes of Ks?

Answer 13

• magnitude of K
• predicting direction of a reaction

Question 14

What can be the magnitude of K?

Answer 14

• large
• small
• around unity

Question 15

What does a large magnitude of K imply?

Answer 15

> 10^2
reaction goes to ‘completion’

Question 16

What does a small magnitude of K imply?

Answer 16

<10^-2
reaction ‘doesn’t occur’

Question 17

What does a around unity magnitude of K imply?

Answer 17

100 - 0.01
all reactants present at equilibrium in significant quantities

Question 18

What ‘stresses’ can you put on an equilibrium?

Answer 18

1. change in concentration of reagent
2. change in pressure of reaction
3. change in temp of reaction

Question 19

What is the Haber process?

Answer 19

N2 + 3H2 -> 2NH3
(ammonia)

Question 20

What conditions does the Haber process have?

Answer 20

• high pressure (300 atm)
• low temp (≈ 450 °C)

Question 21

What are the reaction conditions of the Haber process for Nitrogen Fixation?

Answer 21

• high pressure
• low temp
• remove NH3 as soon as formed
• catalyst

Question 22

What does a catalyst do?

Answer 22

Increases rate of a reaction without undergoing any permanent chemical change.

Question 23

How does a catalyst affect the equilibrium constant?

Answer 23

Does not alter the equilibrium constant
- allows equilibrium to be achieved more quickly

Question 24

What are the effects of change in temp on an equilibrium?

Answer 24

• increase = favours endothermic reactions
• decrease = favours exothermic reactions

Question 25

What is the Law of Mass Action?

Answer 25

When equilibrium is reached, reaction quotient (Q) = number that depends on:
- chemical reaction being considered
- temp of system

Question 26

What is Q renamed as when reactions have reached equilibrium?

Answer 26

Q = K