Le Chatelier's principle

Summary

This video explores Le Chatelier's Principle, a fundamental concept in chemistry concerning reversible reactions at equilibrium. Using cobalt chloride in water, which forms a pink solution, and a blue cobalt chloride complex, the presenter demonstrates how adding hydrochloric acid shifts the equilibrium towards the blue, indicating an increase in chloride ions. Conversely, adding water shifts it back to pink, showing the system's response to minimize changes. The video also highlights the principle's application to temperature, showing that heating promotes endothermic reactions, while cooling favors exothermic ones, providing a practical understanding of how equilibrium adjusts in response to external influences.

Takeaways

• 🔍 Le Chatelier's Principle is a fundamental concept in chemistry that deals with reversible reactions and the state of equilibrium.
• 🌐 When a system at equilibrium is subjected to a change, the equilibrium will shift to minimize that change.
• 💧 The video demonstrates this principle using a chemical reaction involving cobalt chloride in water, which produces a pink solution, and a blue cobalt chloride complex.
• 🔵 The addition of hydrochloric acid, which provides chloride ions, causes the equilibrium to shift towards the blue complex, illustrating the principle in action.
• 🔴 Conversely, adding water to the system shifts the equilibrium back towards the pink cobalt chloride, showing that equilibrium can be adjusted by changing the concentrations of reactants or products.
• 🌡️ Temperature also plays a crucial role in Le Chatelier's Principle, affecting the direction in which the equilibrium shifts.
• 🔥 Heating the reaction causes it to shift in the direction that absorbs heat (endothermic direction), making the blue complex more prevalent.
• ❄️ Cooling the reaction shifts the equilibrium in the direction that releases heat (exothermic direction), favoring the pink cobalt chloride.
• 🧪 The video uses three separate boiling tubes to demonstrate the effect of temperature on the equilibrium, showing clear differences when the solutions are heated, cooled, or left at room temperature.
• 📈 By observing the changes in color and concentration, one can determine whether a reaction is endothermic or exothermic, and predict how it will respond to temperature changes.
• 🔄 Le Chatelier's Principle is applicable to all reversible reactions, providing a way to predict how they will behave under different conditions.

Q & A

What is the main topic of the video?

The main topic of the video is Le Chatelier's Principle, which is an important concept in chemistry related to reversible reactions and equilibrium.

What does Le Chatelier's Principle state?

Le Chatelier's Principle states that when a system at equilibrium is subjected to a change, the equilibrium will shift to counteract that change.

What is the chemical reaction demonstrated in the video?

The video demonstrates the reaction involving cobalt chloride in water, which produces a pink solution, and the addition of hydrochloric acid, which causes the solution to shift towards a blue color due to an increase in chloride ions.

Why does the solution turn blue when hydrochloric acid is added?

The solution turns blue because the addition of hydrochloric acid increases the concentration of chloride ions, causing the equilibrium to shift towards the formation of more of the blue cobalt chloride complex.

What happens when water is added to the equilibrium mixture?

When water is added to the equilibrium mixture, the solution shifts back towards the pink color, indicating that the equilibrium is adjusting to the increased amount of water.

How does temperature affect the equilibrium according to Le Chatelier's Principle?

According to Le Chatelier's Principle, if a system at equilibrium is heated, it will shift in the direction that absorbs heat (endothermic direction). If cooled, it will shift in the direction that releases heat (exothermic direction).

What does the experiment with boiling tubes demonstrate?

The experiment with boiling tubes demonstrates the effect of temperature on the equilibrium. It shows that heating the solution causes it to turn blue (indicating an endothermic reaction), while cooling it causes it to turn pink (indicating an exothermic reaction).

What is the significance of the color changes in the video?

The color changes in the video are visual indicators of the shifts in equilibrium. The transition from pink to blue signifies the effect of added chloride ions, while the shift back to pink upon adding water or cooling shows the system's response to changes in conditions.

Can Le Chatelier's Principle be used to predict the direction of a reaction if it is known to be endothermic or exothermic?

Yes, if it is known whether a reaction is endothermic or exothermic, Le Chatelier's Principle can be used to predict the direction in which the equilibrium will shift when the system is subjected to changes in temperature.

What is the broader application of Le Chatelier's Principle mentioned in the video?

The broader application of Le Chatelier's Principle mentioned in the video is that it applies to all reversible reactions. It can be used to predict how the equilibrium of any reversible reaction will shift when heated or cooled.

Outlines

00:00

🔬 Le Chatelier's Principle and Chemical Equilibrium

This paragraph introduces the concept of Le Chatelier's Principle, which is a fundamental concept in chemistry concerning reversible reactions and equilibrium. The video demonstrates how a system at equilibrium will adjust when subjected to a change, such as the addition of hydrochloric acid to a solution containing cobalt chloride and water. The addition of chloride ions causes the equilibrium to shift towards the formation of more blue cobalt chloride complex, resulting in a color change from pink to blue. The experiment visually illustrates how the system attempts to counteract the change by shifting the equilibrium. The paragraph also touches on the reversibility of the reaction by adding water to revert the color change.

05:01

🔥 The Effect of Temperature on Le Chatelier's Principle

The second paragraph delves into the impact of temperature on Le Chatelier's Principle. It explains that heating or cooling a system at equilibrium will cause the equilibrium to shift in a direction that counteracts the temperature change. The video shows three separate beakers with the same purple solution, subjected to different temperatures: ice (cold), room temperature, and boiling water (hot). The results indicate that heating the solution shifts the equilibrium towards the blue end, suggesting that the blue chemical is endothermic, while cooling it shifts towards the pink, indicating the pink chemical is exothermic. The summary underscores the principle's applicability to all reversible reactions, predicting their direction based on whether they are endothermic or exothermic.

Keywords

💡Le Châtelier's Principle

Le Châtelier's Principle is a fundamental concept in chemistry that describes how a system at equilibrium responds to changes in conditions. It states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the video, this principle is demonstrated by adding hydrochloric acid to a solution containing cobalt chloride, which shifts the equilibrium and changes the color of the solution.

💡Reversible Reactions

Reversible reactions are chemical reactions that can proceed in both the forward and reverse directions under the same conditions. The video script discusses how Le Châtelier's Principle applies to these reactions, showing that changes in the system, such as the addition of more reactants or a change in temperature, will cause the equilibrium to shift to restore balance.

💡Equilibrium

Equilibrium in chemistry refers to a state in which the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products. The video uses the color change in a solution of cobalt chloride to illustrate the concept of equilibrium and how it is affected by the addition of hydrochloric acid.

💡Cobalt Chloride

Cobalt chloride is a chemical compound that, when dissolved in water, produces a pink solution due to the formation of a complex with water molecules. In the video, the color change of the cobalt chloride solution is used to demonstrate the shift in equilibrium when hydrochloric acid is added.

💡Hydrochloric Acid

Hydrochloric acid is a strong acid that, when added to the cobalt chloride solution, provides additional chloride ions. The video demonstrates how the addition of this acid causes the equilibrium to shift towards the formation of more of the blue cobalt chloride complex.

💡Ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net electrical charge. In the context of the video, the chloride ions from hydrochloric acid are shown to affect the equilibrium of the cobalt chloride solution.

💡Endothermic Reaction

An endothermic reaction is a chemical reaction that absorbs heat from its surroundings. The video script explains that when the cobalt chloride solution is heated, the equilibrium shifts towards the endothermic direction, resulting in a bluer color, indicating the formation of the blue cobalt chloride complex.

💡Exothermic Reaction

An exothermic reaction is a chemical reaction that releases heat to its surroundings. The video shows that when the cobalt chloride solution is cooled, the equilibrium shifts towards the exothermic direction, favoring the formation of the pink cobalt chloride complex.

💡Concentration

Concentration in chemistry refers to the amount of a substance present in a given volume. The video demonstrates how changing the concentration of chloride ions by adding hydrochloric acid affects the equilibrium of the cobalt chloride solution.

💡Temperature Effect

The effect of temperature on a chemical reaction is a key aspect of Le Châtelier's Principle. The video script discusses how increasing or decreasing the temperature of the cobalt chloride solution causes the equilibrium to shift in a direction that counteracts the temperature change.

💡Dynamic Equilibrium

Dynamic equilibrium is a state where the forward and reverse reactions occur at the same rate, but the system is still capable of responding to changes in conditions. The video uses the color change in the cobalt chloride solution to illustrate how a dynamic equilibrium can be shifted by adding hydrochloric acid or changing the temperature.

Highlights

Introduction to Le Châtelier's principle, a fundamental concept in chemistry relating to reversible reactions and equilibrium.

Demonstration of how equilibrium shifts in response to changes in a system, minimizing the impact of those changes.

Use of cobalt chloride in water to illustrate the concept of equilibrium with a pink solution.

Explanation of the cobalt chloride complex and its rich blue color, representing one side of the equilibrium.

Visual representation of equilibrium through the mixing of pink and blue chemicals to form a purple solution.

Application of Le Châtelier's principle by adding hydrochloric acid to the equilibrium mixture and observing the color shift towards blue.

Observation that adding chloride ions to the system causes the equilibrium to shift towards the blue chemical to counteract the change.

Experiment showing the reversal of the reaction by adding water, causing the equilibrium to shift back towards the pink chemical.

Discussion on the effect of temperature on Le Châtelier's principle and its influence on the direction of equilibrium shift.

Experiment with three separate boiling tubes to test the effect of temperature on the equilibrium mixture.

Observation that heating the solution causes it to shift towards the endothermic direction, turning the solution blue.

Conversely, cooling the solution causes it to shift towards the exothermic direction, turning the solution pink.

Explanation that the direction of equilibrium shift can indicate whether a reaction is endothermic or exothermic.

Practical application of Le Châtelier's principle to predict the direction of equilibrium shift in response to temperature changes.

Final summary of Le Châtelier's principle and its universal application to all reversible reactions.

Emphasis on the importance of understanding Le Châtelier's principle for predicting the behavior of chemical systems under various conditions.

Transcripts

okay in this video we're going to look

at a important part of chemistry called

lush ateliers principle and this is all

about reversible reactions when they're

at a state we call equilibrium if you

like when they're balanced and less

atelier said when a system that's any

group of chemicals together in a

test-tube relaxed when a system in

equilibrium is subjected to a change the

equilibrium will shift to minimize that

change and hopefully the experiments are

gonna show you now will illustrate that

particular principle now on my left I've

got a chemical called well it's copper

coke pardon it's cobalt chloride but

it's dissolved in water and cobalt

chloride in water produces a pink

solution due to a cobalt iron which has

six water molecules bonded to it

you don't need to know that formula at

GCSE at a two you do but that's another

story

meanwhile on the right hand side we have

a beaker full of cobalt chloride complex

it's a nice rich blue color in the

middle a purple color we've got an

equilibrium of the two different

chemicals mixed together so you've got

some pink and some blue and just like

when you used to mix paints when you

were younger we've got a nice purple

color now let me illustrate

lechatelier's principle I've got some

hydrochloric acid and I'm gonna put a

few drops of that into my beaker in the

middle that's at equilibrium

hydrochloric acid being an acid is got

h+ ions and being a hydrochloric acid

has chloride ions as well and this being

concentrated hydrochloric acid we're

adding a large number of chloride ions

and watch what happens you see the

solution goes blue if I stir it round

it's not fully blue but it's be on a

darker purple a bluer purple and if I

keep adding hydrochloric acid you can

see very intense blue

eventually we will get to a complete

blue we're not quite there yet we've

still got some water present so we've

got the pink chemical and the blue

chemical they're still in equilibrium

now but there's more of the blue unless

the pink because we added more chloride

ions it says English ateliers principle

when a system and equilibrium is

subjected to a change the equilibrium

will shift to minimise the change we

added lots of chloride ions so the

equilibrium shifts this way towards the

blue end to get rid of some of the extra

chloride ions we added those chloride

ions we add some of them will react with

the pink to make more blue now we can

reverse that reaction because we could

add some water now if I just get a

beaker of water if I add a bit of water

back so we're adding something now to

the right-hand side we're increasing the

amount of water in our system just pour

in some water and straight away you

could see pink and didn't take much

water we've already gone back towards

the sort of purple color we started off

with and we're very close to the pink so

that's one thing we can do if we add

more of the chemical on one side on the

left

more chloride ions it shifts towards the

bluer side it goes to the right if we

have more water it goes to the left and

that is lush ateliers principle in

action there is another important thing

to notice with lechatelier's principle

and that's the effect of temperature now

if I just move my blue fluoride

substance and my pink water substance

out the way a minute

I'm going to take my mixture here and

I'm gonna put it in three separate

boiling tubes and I want about the same

amount of each try and do a fair test

and I'll show you in a second that they

look pretty much the same doesn't have

to be exactly the same there we go

similar amounts of three purple

solutions and I'm gonna put one of my

solutions in ice so in it goes I'm going

to leave one of my solutions at room

temperature and in my third my third

solution is going to go in water that I

boiled a couple of minutes ago from the

kettle let's see if we can spot any

difference so we'll give them a few

seconds to shift remember what we've

done according to Lycia today's

principle if we subject an equilibrium

which will change the equilibrium will

shift to minimize that change so if I

heat something up it will go in the

direction that tries to cool it down and

that is the endothermic direction if I

cool it down it will go in the direction

that tries to warm it up the exothermic

direction so much ateliers principle is

a bit like sods law if you try to do one

thing the chemicals will try and do the

opposite I try and heat it up the

chemicals will go endothermic they'll

try and cool down if I cool it down

they'll try and go exothermic they'll

try and get hotter okay they've been in

the beakers for long enough now and if I

take them out okay the difference

between the one on the left in the

middle isn't that great but the one on

the right you can see has gone very blue

so when I make the chemical very very

hot that was the boiling water water

over kettle it goes in the blue

direction when I make the water very

very cold it tries to go back in the

pink direction so this tells us

something important about our reaction

let's just recap then heat it up it goes

blue

so with heat it goes in the blue

direction so going to the right making

the blue chemical must be endothermic

and when I cool it down here's a nice

here's at room temperature it becomes

more pink so when I cool it down the

equilibrium shifts to try and warm up it

goes in the exothermic direction so we

can use less ateliers principle in in

more than one way if we know whether a

reaction is XR endothermic we can

predict which way it will go

if we don't we can do the experiment and

we'll see which way it goes and that

will tell us whether it's X or

endothermic but this idea applies to all

reversible reactions if you heat any

reversible reaction up it will shift in

the endothermic direction cool any

reversible reaction down and it always

goes in the exothermic direction and

that's it the chatelier's principle in a

few simple experiments