6. Chemical Reactions (Part 3) (3/5) (Cambridge IGCSE Chemistry 0620 for 2023, 2024 & 2025)

Summary

This video from IGCC Study Bud covers part three of topic six on chemical reactions, focusing on reversible reactions and equilibrium. It explains the differences between irreversible and reversible reactions, the concept of equilibrium, and the impact of changes in temperature, pressure, and concentration on equilibrium. The video also explores hydrated and anhydrous compounds, highlighting how heat and water affect their reversible reactions. Lastly, it discusses how catalysts speed up reactions without affecting equilibrium. Viewers are encouraged to like, subscribe, and engage in the comment section.

Takeaways

• 🔄 Reversible reactions allow products to revert to reactants, unlike irreversible reactions where the reaction ends.
• ⚖️ Equilibrium is reached in a closed system when the rate of the forward reaction equals the reverse reaction, keeping reactant and product concentrations constant.
• 💧 Hydrated compounds contain water molecules in their structure, while anhydrous compounds do not.
• 🔥 Heating hydrated compounds, like copper sulfate, removes water molecules and turns them anhydrous, changing their color.
• 💦 Adding water to anhydrous compounds reverses the reaction, converting them back to their hydrated forms.
• 🌡️ Changing temperature shifts equilibrium: raising temperature favors the endothermic reaction, while lowering temperature favors the exothermic reaction.
• 💨 In gas reactions, increasing pressure shifts equilibrium towards the side with fewer gas molecules, while decreasing pressure shifts it towards the side with more gas molecules.
• 📊 Changing reactant concentration affects equilibrium: increasing reactants shifts equilibrium toward products, while decreasing reactants shifts it toward reactants.
• ⚗️ Catalysts speed up reactions but do not affect the equilibrium position; they help the system reach equilibrium faster.
• 🎬 The video concludes with a reminder to like, subscribe, and support the channel, and encourages feedback and suggestions.

Q & A

What is a reversible reaction?

A reversible reaction is one where the products of the reaction can react with each other to form the original reactants. This means the reaction can proceed in both directions, from reactants to products and back again.

What symbol is used to represent a reversible reaction?

A reversible reaction is represented by a double-headed arrow symbol (⇌), which indicates that the reaction can go in both directions.

What does it mean for a reaction to be in equilibrium?

Equilibrium refers to a state where the forward and reverse reactions occur at the same rate, meaning the concentrations of reactants and products remain constant over time in a closed system.

What are hydrated compounds?

Hydrated compounds are substances that have water molecules trapped within their structure.

What are anhydrous compounds?

Anhydrous compounds are substances that do not contain water molecules within their structure.

How does heating affect hydrated compounds?

Heating hydrated compounds causes them to lose their water molecules and become anhydrous. For example, heating hydrated copper(II) sulfate changes its color from blue to white as it becomes anhydrous.

How does adding water to anhydrous compounds affect them?

Adding water to anhydrous compounds can cause them to regain their water molecules and revert to their hydrated form. This change is reversible, as seen with anhydrous copper(II) sulfate turning back to its blue hydrated form when water is added.

What factors affect the position of equilibrium in a reversible reaction?

The position of equilibrium can be affected by changing conditions such as temperature, pressure (for gaseous reactions), and the concentration of reactants or products.

How does changing temperature affect the position of equilibrium?

Raising the temperature shifts the equilibrium towards the endothermic reaction to absorb heat, while lowering the temperature shifts it towards the exothermic reaction to release heat.

How does pressure affect equilibrium in gaseous reactions?

Increasing pressure shifts the equilibrium towards the side of the reaction with fewer gas molecules to reduce pressure. Decreasing pressure shifts it towards the side with more gas molecules to increase pressure.

Outlines

00:00

📚 Introduction to Reversible Reactions and Equilibrium

This paragraph introduces the concept of chemical reactions, focusing on reversible reactions and equilibrium. Irreversible reactions complete once products form, while reversible reactions allow products to revert to reactants. A reversible reaction occurs when products can re-form the original reactants. The equilibrium point in a reversible reaction is when both forward and reverse reactions occur at the same rate, leading to constant concentrations of reactants and products. The discussion also covers how changes in conditions, such as heat, can affect reversible reactions.

05:01

💧 Hydrated vs. Anhydrous Compounds and Heat Effects

This section explains the difference between hydrated and anhydrous compounds, using copper(II) sulfate and cobalt(II) chloride as examples. Hydrated compounds contain water molecules in their structure, while anhydrous compounds do not. Heating hydrated compounds removes the water molecules, turning them into their anhydrous form, as seen with blue hydrated copper(II) sulfate becoming white anhydrous copper(II) sulfate. The process is reversible—adding water to anhydrous compounds restores their hydrated form. For example, anhydrous cobalt(II) chloride changes from blue back to pink when hydrated.

10:02

⚖️ Equilibrium Position and Factors Affecting It

This paragraph delves into the concept of the equilibrium position, which describes the balance of reactants and products in a reversible reaction. Several factors, including temperature, pressure, and concentration, influence the equilibrium position. The reaction adjusts to counteract changes, such as temperature increases favoring the endothermic direction. Pressure changes affect reactions involving gases, with higher pressure shifting equilibrium towards fewer gas molecules. Using a specific reaction example involving carbon monoxide, hydrogen, methane, and water vapor, the paragraph demonstrates how changing pressure affects equilibrium shifts.

🔄 Concentration, Catalysts, and Equilibrium Balance

The final section discusses how changes in reactant concentration influence the equilibrium position. Increasing reactant concentration pushes the equilibrium toward forming more products, while decreasing it shifts equilibrium toward the reactants. The paragraph emphasizes that catalysts, while speeding up reactions, do not change the equilibrium position—they simply help the system reach equilibrium faster. The conclusion reinforces that catalysts affect reaction rates but not the amounts of products or reactants at equilibrium.

Keywords

💡Reversible Reactions

A reversible reaction is one where the products can react to reform the original reactants, allowing the reaction to go both forward and backward. This concept is central to the video as it explains how certain chemical reactions, such as the hydration and dehydration of copper sulfate, can change direction based on external conditions like heat or water addition.

💡Equilibrium

Equilibrium refers to the state in a reversible reaction where the forward and reverse reactions occur at the same rate, resulting in constant concentrations of reactants and products. The video discusses how equilibrium is maintained in a closed system and how external factors like temperature and pressure can shift the balance of the reaction.

💡Hydrated Compounds

Hydrated compounds are substances that contain water molecules within their structure. In the video, hydrated forms of salts like copper sulfate (which is blue) and cobalt chloride (which is pink) are highlighted to show how heat can drive off the water molecules and convert them to their anhydrous forms.

💡Anhydrous Compounds

Anhydrous compounds are substances that do not contain water molecules within their structure. In the video, anhydrous copper sulfate and cobalt chloride are examples used to demonstrate how the absence of water changes the physical properties, such as color, of these salts when they lose their hydration.

💡Le Chatelier’s Principle

Le Chatelier's Principle explains how a system at equilibrium will adjust to counteract changes in conditions like temperature, pressure, or concentration. The video references this principle when explaining how the equilibrium position shifts in response to these changes, such as favoring the endothermic or exothermic reaction based on temperature adjustments.

💡Exothermic Reaction

An exothermic reaction is one that releases heat to its surroundings. The video explains how lowering the temperature will favor the exothermic direction of a reversible reaction, as the system tries to produce more heat to counteract the change in temperature.

💡Endothermic Reaction

An endothermic reaction is one that absorbs heat from its surroundings. In the video, increasing the temperature shifts the equilibrium toward the endothermic reaction, as the system seeks to absorb the excess heat, demonstrating how temperature can influence chemical reactions.

💡Pressure

Pressure plays a role in shifting equilibrium in reactions involving gases. The video explains that increasing pressure shifts equilibrium toward the side with fewer gas molecules, as seen in the reaction of carbon monoxide and hydrogen forming methane, where pressure changes affect the balance between reactants and products.

💡Concentration

Concentration affects the equilibrium of a reaction by shifting it towards the side that balances any changes. Increasing the concentration of reactants causes the system to produce more products, and vice versa. The video uses this concept to illustrate how changes in concentration drive the reaction in different directions.

💡Catalyst

A catalyst speeds up both the forward and reverse reactions without affecting the position of equilibrium. The video emphasizes that while catalysts help reactions reach equilibrium faster, they do not alter the balance between reactants and products once equilibrium is reached.

Highlights

Introduction to reversible and irreversible reactions, defining key terms.

Explanation of reversible reactions where products can convert back to reactants.

Definition of equilibrium: when forward and reverse reactions occur at the same rate.

Concept of a closed system and how equilibrium is maintained with constant reactant and product concentrations.

Description of hydrated and anhydrous compounds with copper (II) sulfate and cobalt (II) chloride as examples.

Impact of heat on hydrated compounds, turning them anhydrous, demonstrated with copper (II) sulfate changing from blue to white.

Reversibility of hydration reactions shown by adding water to anhydrous copper sulfate, which turns blue again.

Cobalt (II) chloride changing color from pink to blue when losing water and reverting when water is added.

Explanation of how the equilibrium position is affected by external factors like temperature, pressure, and concentration.

Effect of temperature changes on equilibrium: endothermic and exothermic reactions shifting balance.

Pressure changes impacting equilibrium in reactions involving gases by shifting toward fewer or more gas molecules.

Example of pressure effect using carbon monoxide and hydrogen gas reaction producing methane and water.

Influence of concentration on equilibrium: increasing reactant concentration shifts balance towards products.

Catalysts' role in speeding up reactions without changing the equilibrium position.

Concluding part of the video encouraging viewer engagement and explaining the purpose of the channel for IGCC study.

Transcripts

hi everyone welcome to igcc study bu

where you can revise chemistry topics

from the Cambridge igcs

syllabus if you are enjoying our video

so far please don't forget to hit the

like button and subscribe to our

channel in this video you are going to

learn part three of topic six chemical

reactions

first up reversible reactions and

equilibrium in some reactions the

reactants are completely converted to

products and then the reaction is just

over these are called irreversible

reactions on the other hand some

reactions can go backward meaning the

products can turn back into the original

reactants these are reversible reactions

a reversible reaction is one where the

products of the reaction can react with

each other to form the original

reactants in a reversible reaction the

reaction can proceed in both directions

and this is shown by this

symbol so if a chemical reaction has

this symbol instead of the normal Arrow

then we know it's a reversible reaction

and it can go forward or

backward what is

equilibrium equilibrium refers to a

state where the forward and reverse

reactions in a reversible reaction occur

at the same rate in simpler terms it's

like a balance point where the

concentrations of reactants and products

remain constant over time

so a reversible reaction in a closed

system is at equilibrium when the rate

of the forward reaction is equal to the

rate of the reverse reaction and the

concentration of reactants and products

are no longer

changing let's explore the effects of

changing conditions on reversible

reactions what are hydrated compounds

hydrated compounds are substances that

have water molecules trapped within

their

structure what are anhydrous compounds

anhydrous compounds are substances that

do not contain water molecules within

their

structure both copper 2 sulfate and

Cobalt 2 chloride can exist in both

hydrated and and anhydrous forms that

means they can have water molecules in

them making them hydrated or they can be

without water which makes them

anhydrous first let's take a look at the

effect of heat on hydrated

compounds heating hydrated compounds

makes them lose their water molecules

and become anhydrous

hydrated copper two sulfate is a blue

crystal salt when heat is added to it it

loses its water molecules and becomes

anhydrous it changes color from Blue to

White now let's describe how the

addition of water to anhydrous compounds

can change the direction of a reversible

reaction adding water to anhydrous

compounds can cause them to regain their

water molecules and revert to their

hydrated

form the above change is reversible so

when the water is added to anhydrous

copper to sulfate it can revert back to

its blue hydrated

form Cobalt to two chloride is another

example of a salt that can clearly show

a color change when switching between

its hydrated and anhydrous forms Cobalt

2 chloride is a salt that is pink in its

hydrated form heating it makes it lose

its water molecules and it becomes

anhydrous changing color from pink to

blue when water is is added to anhydrous

Cobalt to Chloride it can revert back to

its pink hydrated

form the equilibrium position shows how

much of each substance is present when a

reaction is

balanced for a reversible reaction the

position of equilibrium changes due to

some adjusting

factors this means the balance between

reactants and products

changes these factors affect the

position of

equilibrium changing

temperature changing pressure and

changing

concentration when a reversible reaction

is at equilibrium and then these

external factors are introduced the

reaction system will will respond by

trying to do the opposite to counteract

the change and keep everything

balanced that is restore

equilibrium If It Moves right more

products are made and reactants

decrease If It Moves left more reactants

are present and products

decrease changing temperature in a

reversible reaction One reaction

releases heat that is exothermic while

the other absorbs heat that is

endothermic raising the temperature

shifts the equilibrium toward the

endothermic reaction to absorb heat

while lowering the temperature shifts it

towards the exothermic reaction to

release heat remember these happen to

oppose the

change if the forward reaction is

endothermic raising the temperature will

cause the system to favor the forward

endothermic reaction to absorb the

excess heat thereby Shifting the

equilibrium towards the endothermic

reaction similarly if the forward

reaction is endothermic lowering the

temperature will make the system favor

the backward exothermic reaction to

release more heat Shifting the

equilibrium towards the exothermic

reaction changing pressure this Factor

applies only in reactions with gases we

have to look at the number of moles in

the

reaction increasing the pressure causes

the equilibrium position to shift

towards the side that has fewer gas

molecules this is because the system is

trying to reduce the pressure by

preferring the reaction that produces

fewer gas particles in order to

counteract the pressure increase

remember fewer particles mean lower

pressure let's consider the reaction of

carbon monoxide and hydrogen gas to

produce methane gas and water vapor in

this reaction on the reactant side we

have 1 mole of carbon monoxide gas and 3

mes of hydrogen gas totaling four moles

of gas on the product side we have 1

mole of methane gas and 1 mole of H2O

gas totaling 2 mol of

gas now let's consider the effect of

increasing the pressure

there are more gas molecules on the

reactant side than the product side so

the equilibrium Position will shift to

the right towards the side with fewer

gas molecules the produ side in order to

reduce the

pressure alternatively if the pressure

is decreased the equilibrium Position

will shift towards the side with more

gas molecules which is the reactant side

towards the left this shift occurs to

increase the pressure by favoring the

reaction that involves more gas

molecules changing the pressure only

matters if there are different number of

gas molecules on each side of the

reaction if both sides have the same

number of gas molecules pressure changes

won't affect the equilibrium

position changing the concentration of

reactants will move the equilibrium

position to do the opposite of the

change when we increase the

concentration of reactants the

equilibrium position shifts towards the

products in order to balance it

resulting in an increase in the amount

of products formed

likewise if we reduce the concentration

of reactants the equilibrium shifts

towards the reactants resulting in a

decrease in the amount of products

formed if there's too much of a product

the reaction decreases its amount to

balance the reaction conversely if

there's not enough product the reaction

produces

more very important using a catalyst

will not affect the position of

equilibrium this means that adding a

catalyst won't make the reaction produce

more products or more reactants when it

reaches its balance point but they speed

up reactions they only increase the rate

of reaction they help the reaction reach

equilibrium Faster by increasing the

rate of both the forward and reverse

reactions that concludes part three of

topic six chemical

reactions are you enjoying our videos

are they helping you here's a way you

can show your appreciation and support

our continued efforts you may use

YouTube super thanks to send us thanks

hope this video helped you please share

your thoughts and suggestions in the

comment section thank you for watching

and please don't forget to subscribe to

igcc study Budd for more revision videos

bye