Topics:

• Rate of Reaction:
  • Calculating rate of reaction
  • Collision Theory
  • Catalyst
  • Factors affecting rate of reaction
  • Investigating effects of Concentration, Particle Size, Temperature and Pressure
• Redox
  • Oxidation and Reduction
  • Oxidation State
  • Oxidizing and Reducing Agents
• Reversible Reactions
  • Reversible reaction
  • Irreversible reaction
  • Equilibrium
  • Dynamic Equilibrium
  • Factors that affect equilibrium

Rate of Reaction:

The speed at which a chemical reaction proceeds is called the rate of reaction.

Calculating Rate of Reaction:

There are two main ways of calculating the rate of a reaction: Measuring Rates: We commonly use two ways to measure the rate of a reaction.

Measuring Rates:

We commonly use two ways to measure the rate of a reaction.

We attach a syringe to a reaction that gives off gas and measure the rate of gas discharge

Measuring Rates: We commonly use two ways to measure the rate of a reaction.

• We attach a syringe to a reaction that gives off gas and measure the rate of gas discharge

• We place the reaction apparatus on a balance and measure the rate of change of mass

We place the reaction apparatus on a balance and measure the rate of change of mass

Collision Theory:

Collision theory states that in order to react with each other, particles must collide in the correct orientation and with a specific energy.

Catalyst:

• Catalysts are substances that speed up a reaction by lowering the activation energy of a reaction.
• Enzymes are called biocatalysts since they speed up chemical reactions in living organisms.
• In industrial processes, transition metals and their compounds are used as catalysts. (transition metal discussed in periodic table).

Factors affecting rate of reaction:

Temperature:

Generally, increasing the temperature will cause the particles to speed up and collide more frequently. This will result in an increase in the rate of the reaction.

• If the reaction in endothermic, it requires heat to proceed. In this case, increase in temperature will increase the rate of the reaction.
• If the reaction is exothermic, heat in the surrounding will not help the reaction to proceed.

Pressure:

Increase in pressure mean that the particles are closer together and there is a higher chance of collision between the particles. Hence, the rate of the reaction will increase.

Concentration:

A higher concentration means that there are more particles available for the reaction and hence, there is a higher chance of the reaction to happen when particles collide. Hence, the concentration also increases the rate of the reaction.

Particle Size:

When particles are in smaller chunks, they have more surface area. This means that there is a higher chance for the particles to collide in the correct orientation and hence, smaller particle size will result in an increase in the rate of reaction.

Catalysts:

By the addition of catalysts, speed of a reaction increases since the initiation time of the reaction decreases due to decreased activation energy.

Investigating effects of Concentration, Particle Size, Temperature and Pressure:

• Concentration:
  • Carry a chemical reaction with a set of specific concentrations and time the reaction completion using either of the two formulas.
  • Repeat with an increased concentration of one of the reactants with all other conditions same to first experiment.
• Particle Size:
  • Measure the mass of a reactant e.g. metal strip and react it with for example, acid. Time the reaction.
  • For the second experiment, use the same mass of the reactant but in refined power form and keep all the other test conditions same.
• Temperature and pressure:
  • Carry out two experiments for each with only the said quantity being changed and time the reaction to calculate its speed each time for comparison.

Redox:

The term redox is a combination of two processes, reduction and oxidation. The reactions that contain reduction and oxidation are called redox reactions.

Oxidation and Reduction:

Oxidation State:

The charge of an atom or ion in a compound. The elements in group 1 and 2 of the periodic table have the same oxidation state as their valency.

Calculating Oxidation State:

We place all the oxidation states that are known to us in an equation and equate them to zero since a compound has no charge. Then we find the wanted oxidation state. Example: We have to find the oxidation state of Chlorine in NaClO3:

• Na is in group 1 and has an oxidation state of +1,
• Oxygen has an oxidation state of -2,
• So (+1) + Cl + 3(-2) = 0 (3 times since oxygen has 3 atoms in one molecule of the compound.
• This calculates the oxidation state of chlorine as +5 in this compound.

Oxidizing and Reducing Agents:

Oxidizing Agent:

• A substance that helps oxidation to take place is called an oxidizing agent.
• In a reaction, an oxidizing agent itself gets reduced to oxidize another.
• K₂Cr₂O₇, KMnO₄, non-metals.

Test for Oxidizing Agent:

Add some solution of potassium Iodide (KI) to the substance. If its color changes from brown/ reddish to colorless, the substance is an oxidizing agent.

Reducing Agent:

• A substance that helps reduction to take place is called a reducing agent.
• In a reaction, a reducing agent itself gets oxidized to reduce another.
• H₂, CO, KI, metals.

Test for Reducing Agent:

• Add some solution of KMnO₄ to the substance. If its color changes from purple to colorless, the substance is a reducing agent.
• Add some solution of K₂Cr₂O₇ to the substance. If its color changes from orange to green, the substance is a reducing agent.

Reversible Reaction:

A chemical reaction that can proceed in both directions is known as reversible reaction. It has a ⇌ sign in the equation.

Examples of Reversible Reactions:

With equilibrium:

• Haber process: 3H₂ + N₂ ⇌ 2NH₃
• Contact Process: 2SO₂ + O₂ ⇌ 2SO₃
• Manufacture of Nitric Acid: 2NO + O₂ ⇌ 2NO₂
• Carbonic Acid: H₂CO₃ ⇌ 2H + CO₃

Without equilibrium:

• CuSO₄.5H₂O → CuSO₄ + 5H₂O
• Blue hydrated copper sulfate, which is a crystalline form, turns to anhydrous copper sulphate which is an amorphous/ powder form.
• Forward reaction:
  • CuSO₄.5H₂O → CuSO₄ + 5H₂O
• Backward Reaction:
  • CuSO₄ + 5H₂O→ CuSO₄.5H₂O

Irreversible Reactions:

Many reactions go towards their completion. Such reactions are called Irreversible reactions.

Equilibrium Reaction:

A reaction in which the products react together to form the original reactants at the same time that reversible reaction is called equilibrium reaction.

Dynamic Equilibrium:

Dynamic equilibrium is when the reactants are continuously being changed into products and the products are continuously being changed into reactants simultaneously.

Conditions for dynamic equilibrium:

• Forward and backward reaction must occur at the same time.
• The concentration of reactants and products remain constant at equilibrium.
• Forward and backward reactions occur at the same rate.
• There should be a closed system: nothing should escape the system.

Factors that affect equilibrium:

Concentration:

Wherever the concentration is less, the equilibrium will shift to that side.

Catalyst:

Catalyst will speed up the reaction and hence the equilibrium will be achieved faster.

Lesson Tags

Chemical Reactions | Rate of Reactions | Redox Reactions | Detailed Notes For Preparation & Revision | O Level Chemistry 5070 and IGCSE Chemistry 0620

Our Affordable Paid Courses

Courses Page: https://educateachange.com/courses

Paid Courses For O Level/ IGCSE Chemistry

To get the latest content, updated and detailed notes, video lectures, live classes, quizzes, assignments personally marked by Sir Hunain (past paper-based assignments) and much more, consider our paid courses.

Biology Crash Course Link: https://educateachange.com/courses/caie/chemistry-0570-or-chemistry-0620-or-chemistry-0971-o-level-or-igcse-crash-course/

Biology Full Scale Course Link: https://educateachange.com/courses/caie/chemistry-0570-or-chemistry-0620-or-chemistry-0971-o-level-or-igcse-full-scale-course/

Free Education

Check out more free material at our Free Education Section

Free Education Link: https://educateachange.com/free-education

Ask Your Question Link: https://educateachange.com/forums/forum/free-education-forum/

Contact Information

Whats App: +92 336 311 1855

Email: free@educateachange.com

Social Media For Hunain Zia

YouTube: AYLOTI

Facebook: Official Facebook Page

Instagram: Official Instagram Page

LinkedIn: Official LinkedIn Profile

TikTok: Official TikTok Profile

Twitter: Official Twitter Profile

SnapChat: Offical SnapChat Account

Free Education Groups

Facebook General Free Education Group: Real Free Education

Facebook CAIE Free Education Group: AYLOTI Education

Fair Usage Policy

NOTE: To ensure fair use and legal use of this material, please note the following: plagiarism, copying, saving, distribution, re-distribution, cross-posting and using this content on ANY other platform or website is prohibited.