Equilibrium

Chapters 7&8

Introduction

• What is equilibrium?

• What happens to the water in a open bottle over a period of time?

• What happens to the water in a closed bottle over a period of time?

Types of Equilbrium

• Solubility– Solute dissolving into a solvent.– A point is reached where some solute will

dissolve while some other solute will reform into a solid form at the same time

Solubility Equilibrium

• Some of the Silver chloride will remain as a solid while some will dissolve to go into solution. Over time some of the particles dissolved will return to the solid form while others dissolve. See page 426 and 427

Phase equilibrium

• How do you like your coke?

• How do you prevent the previous?

• What makes the fizz?

• What keeps the fizz?

• What happens when you open the bottle?

• Again and again and again and again?

• What is the pop in the bottle trying to do?

• What is pop?– Water + syrup + bubbles ( ________)– What makes a good pop?

– How do bubbles get into and stay in the water? High P___________.

– When high P________ is released……..

– How do you keep the pop fizzy? Ideas?

Chemical Reaction Eq.

• What normally happens in chemical reactions?– They go to _______________

– However sometimes things do not always proceed this way.

– Industrial processes sometime require batch processing which is competed in a closed container which will influence how the chemical reaction will proceed.

• Reaction of hydrogen and Iodine in a closed system

• Initially in the reaction vessel there are only the reactants.

• Over time, the reactants react with each other to form products.– However, do all reactants react?– What do you observe in the vessel once

equilibrium is reached?

• Equilibrium state– This condition is illustrated by the presence of

both reactants and products in the closed reaction vessel once the reaction has attained a steady state.

– It appears as if nothing is going on however on a molecular level there is much activity which is the basis of DYNAMIC EQUILIBRIUM.

Percent Reaction at Equilibrium• Equilibrium reactions can be assessed similar to

stoichiometric measurements to give a picture of HOW MUCH of each species is present.

• Since chemical reactions are considered to be reversable, it is important to understand to what extent the reaction proceeds and in what direction, toward the products or the reactants.

• 1 % reaction. Reactants favoured. No real chemical reaction occurring

• >99 % reaction Products favoured. Reaction virtually complete, hardly any reactants present

• % values between these two extremes, significant amounts of reactants and products present. An equilibrium has been established between the two.

Equilibrium and Stoich Calcs

• Generally reactions proceed towards completion.

• Some situations involve chemical reactions where amounts of all SPECIES are present in the initial reaction vessel prior to reaching the EQUILIBRIUM STATE.

• Analysis of this reaction can be completed

Analysis of Eq. Data

Equilibrium Calculations are always completed using values for reactants and products in CONCENTRATION FORM.

2 moles of A in a 2.5 L container.

c = n/v Therefore 2 moles/ 2.5 L =?

ICE CHARTS

• Analysis of data for equilibrium reactions requires a look at the WHOLE PICTURE.

• Before and after “SHOTS” and compare

• ICE charts help organise data• I initial concentrations of all• C change in concentrations• E concentrations of all at Eq. conditions

Sample Prob

• H2 + F2 HF

• What are concentrations of all species at beginning of reaction and when Eq is reached?

• Write out Given information• Initial conditions [H2] & [F2] 1.0 mol/L• [HF] = 0.0 mol/L• Eq conditions [H2] & [HF] = unknown

– [F2] = 0.24 mol/L

ICE chart example

• Fill in chart• Reaction shows Hydrogen reacting with Fluorine to form HF• As product is formed, a certain amount of reactants are used up

thus leading to decrease of reactants once EQ is reached.• How much is the decrease? Change?

H2 +

F2 <==> HF

I ( initial concentration) 1.0 mol/L 1.0 mol/L 0.0 mol/L

C ( change in concentration

E ( equilibrium conditions) 0.24 mol/L

• Can you solve anything from ICE chart?• Initially ?_____________

• From the ICE chart you can then do math.

• Textbook work page 437 # 6&7• Page 437 section 7.1 question #4