O Level Chemistry & IP Chemistry Notes by 10 Year Series Author - Chemistry Specialist

O Level Chemistry Made Easy

O-Level Chemistry: Tests for Oxidising Agents and Reducing Agents

Test for Oxidising Agents and Reducing Agents - O Level Pure Chemistry Tuition
Photo Credit: Pete (Creative Commons)

Today, we shall take a look at the Tests for Oxidising Agents and Reducing Agents using common chemical reagents in our school laboratories.

Before we can continue, is important to first understand what is a Redox Reaction and how to identify one.

You will also need to know the definitions of Oxidising Agents and Reducing Agents.

A reducing agent is a substance that reduces another substance by:

  • giving hydrogen to the substance
  • removing oxygen from the substance
  • giving electrons to the substance

In the process of reducing another substance, the reducing agent itself becomes oxidised.

Common Reducing Agents are:

  • Potassium iodide, KI (colourless solution)
  • Reactive metals such as Mg, Zn
  • Hydrogen gas, H2
  • Carbon, C
  • Carbon monoxide, CO
  • Hydrogen sulfide, H2S
  • Sulfur dioxide, SO2
  • etc

while

An oxidising agent is a substance that oxidises another substance by

  • giving oxygen to the substance
  • removing hydrogen from the substance
  • receiving electrons to the substance

In the process of oxidising another substance, the oxidising agent itself becomes reduced. I have blogged about these agents before using the analogy of a property and an insurance agents.

Common Oxidising Agents are:

  • Acidified potassium manganate (VII), KMnO4 (purple solution)
  • Acidified potassium dichromate (VI), K2Cr2O7 (orange solution)
  • Halogens e.g. Cl2, Br2
  • Concentrated sulfuric acid, H2SO4
  • Nitric acid, HNO3
  • Oxygen, O2
  • etc

In the video below, i will share with you on the step-by-step strategy to test for Oxidising and Reducing Agents using common laboratory reagents such as aqueous potassium iodide, KI(aq) and acidified potassium manganate (VII), KMnO4(aq) solutions.

Test for Oxidising Agent:

Use of a Reducing Agent e.g. aqueous potassium iodide, KI(aq)

Observation: Colourless solution turns brown

Chemistry behind it: 2I–(aq) => I2(aq) + 2e–

Test for Reducing Agent:

Use of an Oxidising Agent e.g. acidified potassium manganate (VII)

Observation: Purple solution decolourises

Chemistry behind it: MnO4–(aq) + 8H+(aq) + 5e– => Mn2+(aq) + 4H2O(l)

YouTube Video Tutorial

Let’s take a look at the YouTube Video now….

Length of video: 16.11 minutes

Direct video link: https://youtu.be/1YQsHwUrT2c

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends and learn the key O-Level Pure Chemistry concepts together.

Subscribe to my blog to receive 2 updates per month sent to your email!

PS: Under related articles below, there are several blog post discussions and questions related to Redox Reaction concepts. You can also do a keyword search using the search box at the top right hand corner.

O-Level-Pure-Chemistry-Pass-With-Distinction-Workshops

O-Level Chemistry: 4 Ways to Identify A Redox Reaction (Oxidation & Reduction)

Rusting is a Redox Reaction - O Level Pure Chemistry Tuition
Photo Credit: Ed Suominen (Creative Commons)
Do you know that Rusting of Iron and Steel is a Redox Reaction?

A redox reaction is a chemical reaction whereby both oxidation & reduction occurs simultaneously.

The word “REDOX” comes from the words REduction and OXidation.

So, how do you know if a redox reaction has taken place?

There can be more than one way of identifying a particular chemical reaction as a redox reaction. This also mean that not all chemical reactions are redox reactions.

4 Ways to Identify a Redox Reaction

1) Gain or loss of oxygen

2) Gain or loss of hydrogen

3) Gain or loss of electrons

4) Increase or decrease in oxidation state

Oxidation has taken place if a substance:

  • gains oxygen
  • loses hydrogen
  • loses electrons
  • increases its oxidation state after a reaction

Reduction has taken place if a substance:

  • loses oxygen
  • gains hydrogen
  • gains electrons
  • decreases its oxidation state after a reaction

In the following YouTube Video, you will learn EVERYTHING you need to know to determine whether a chemical reaction involves redox reaction. This video is exactly what we taught Sec 3 and Sec 4 students in our O-Level Pure Chemistry Tuition Classes. This applies to IP and IGCSE students in our classes as well.

Step-by-step strategies as well as some common rules are also being discussed when it comes to gain/loss of electrons and increase/decrease in oxidation state.

Do note that questions based on gain/loss of electrons and increase/decrease in oxidation state tends to be more tricky in Chemistry examination.

Length of video: 16.02 minutes

Direct video link: https://youtu.be/sUU1YSnWBnQ

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends and learn the key O-Level Pure Chemistry concepts together.

In the next blog post, i will be sharing with you on the concepts of Oxidising Agents and Reducing Agents, and also how to identify them using common reagents in the school laboratories.

Subscribe to my blog to receive 2 updates per month sent to your email!

PS: Under related articles below, there are several blog post discussions and questions related to Redox Reaction concepts. I will list some of these older blog posts below.

Redox Reaction based on Oxygen Atoms

Redox Reaction based on Hydrogen Atoms

Tips on Assigning Oxidation States

You can also do a keyword search using the search box at the top right hand corner.

“Leap from O-Level Chemistry to A-Level H2 Chemistry”

To qualify for taking up H2 Chemistry, some JCs have the requisite that students must have a minimum B3 grade for O-Level Pure Chemistry or A2 for Combine Science Chemistry. There’s an obvious reason for this condition as A-Level H2 Chemistry syllabus is demanding in terms of content. If you are posted to a JC, lessons usually start in mid February and are you aware that your promotional examination can start as early as mid September.  This means you only have about 6 months of studying period. Do not expect any revision as most lecturers are rushing to complete the syllabus for examination.

JC1 will be over before you know it! Imagine getting used to the new school environment, new friends, new lecture-tutorial system, new expectations from your parents, friends and school, all these can be really stressful if you did not manage well. Every year, my students asked me the same questions about JC life, in particular,

  • Should I take H2 Chemistry since I only scored an A2 for O-Level Pure Chemistry?
  • What’s so challenging about H2 Chemistry since I have learnt Chemistry at O-Level? Isn’t it just an add-on?
  • How can I prepare myself to handle H2 Chemistry confidently?

I would like to share my experience as a Ten Years Series author for O-Level and A-Level Chemistry to the above questions and more. After having taught students from almost every JCs, I come to understand the challenges, the struggles JC1 students go through and by knowing how to handle the transition from O-Level to A-Level effectively, not only do you have a memorable 2 years of JC, it will also pace you for tertiary education. Join me in this free talk! I look forward to meeting you!

Title of talk: “Leap from O-Level Chemistry to A-Level H2 Chemistry”

Date: 6 Feb 2018 (Tuesday)

Time: 7 – 830pm

Venue: Winners Education Centre Pte. Ltd. Blk 261, Waterloo St, #03-21, Waterloo Centre Singapore 180261

For: Students (& Parents) who have decided on or considering H2 Chemistry as an A-Level subject

Registration is closed. If you would like to attend the 2019 session, please SMS us at 9828 7357

Small group sharing with questions and answers session from parents/students at the end of talk. Parents are enlightened and students are mentally ready to start the tricky and rigorous JC1 curriculum.

O-Level Pure Chemistry Final Revision: Score 100% Chemistry MCQ Workshop (9th Year!)

  1. Do you lack the motivation to continue with thorough preparation for your Pure Chemistry MCQ paper when you just study for Chemistry structured paper 15 days ago?
  2. Are you uncertain of how to prepare effectively for your MCQ?
  3. Are you simply going to flip through your notes and textbook on the eve of your MCQ paper and thinking that it is sufficient for you to continue in the paper?
  4. Are you overly confident of your ability that you do a slipshod revision instead of paying to details, recapping essential concepts?

For the 9th consecutive year, Score 100% O-Level Pure Chemistry MCQ Workshop has helped hundreds and hundreds of students from more than 170 schools to prepare Chemistry MCQ with

  • the right mindset (regardless of how you think you have fared for Paper 2)
  • tested and proven strategies to score confidently in MCQ within 60 minutes
  • highlighting of the common mistakes
  • the strategies to complete the MCQ paper fast and accurate even with time for checking (This is the secret why students can score 100% for Chemistry MCQ, you have time to check our answers while your friends struggle to complete the questions!)

Many people know me as the Master Trainer for Chemistry in Winners Education as well as Ten Year Series book author.

Over the last 18 years, I have coached thousands and thousands of students from over 170+ schools to achieve the marks they truly deserve. I have also rekindled their interest in Chemistry so much so that many of them are furthering their study in chemistry-related courses and in fact, a handful of them will be joining the booming chemical industry.

Join me and a group of committed students on 11 November 2017 (Sat) for Score 100% Pure Chemistry MCQ Workshop by clicking on the button below!

“This programme tells me the topics that I am weak in and it emphasises the importance of getting full marks for Chemistry MCQ. I have learnt to manage my time wisely, which is crucial in doing Paper 1 as I usually could not finish the paper. I learnt more about the strategies of doing MCQ and revise on key concepts. I hope I am able to get full marks and I will recommend this to anyone taking O-Levels.” Cher Yi Jia, Nan Hua High

“It has benefited me by giving me the chance to practise. It has also helped me to revise and remind me what I have forgotten.” Ryan Lee, Chung Cheng High School (Main)

It is good that Sean has organized this workshop to focus on the MCQ of Chemistry paper as it is often a paper that teachers and students alike will neglect. Through the workshop, he covers tricky and common MCQ questions, which is very helpful. His cheerful and lively teaching approach learns to keep everyone awake and in focus. Thanks Sean for everything! Definitely recommended to other students in future. Edna Chan Zhi Yin, Hougang Sec School

 

 

Master O-Level Organic Chemistry in 2 Days!

I am Sean Chua, Master Trainer for Chemistry in Winners Education. Many students and parents also know me as the Ten Years Series author for O-Level & A-Level Chemistry.

Do you know there are less than 3 months to the O-Level Pure Chemistry Paper 2?

What this means is ‘Are you ready in your basic Chemistry concepts and application skills to score confidently in this year O-Level Chemistry examinations?’

I have been conducting the Organic Chemistry Topical Workshop since 2008 to help struggling students to

  • Summarize large junk of information into digestible bits
  • Understand this major topic clearly
  • Solve data-based application questions, guaranteed to be tested in examinations
  • Reduce memory work to a minimum
  • Score as high as possible in this heavy weighting topic!

Some of you might wonder about the effectiveness of this workshop since it is so near to O-Levels!

This is precisely the reason why I am still conducting this workshop during this period as most schools teach Organic Chemistry as the last topic in a rush rush manner and most students are unable to understand, find it confusing.

Are you one of them?

Since Organic Chemistry consists of many small subsections, many students are overwhelmed with the huge amount of content and thus lose confidence in their Chemistry.

She can understand your lesson very well and for the first time, she says she likes Chemistry. Thank you for rekindling her interest in Chemistry. She has also expressed her interest in the weekly class.
Mr Cher, Father of Cher Yi Jia, Nan Hua High School, D7 to A2 in 4 months!

I will be covering 100% of O-Level Organic Chemistry. It includes the following:

  1. Fuels & Crude Oils
  2. Homologous Series & Functional Groups
  3. Naming of Organic Compounds
  4. Isomerism
  5. Alkanes
  6. Alkenes
  7. Alcohols
  8. Carboxylic Acids
  9. Esters
  10. Macromolecules
  11. Application Questions

Organic Chemistry Workshop

Date & Time: 9 & 10 August 2017, 9am to 1pm

Bonus Booster Session

Date & Time: 31 August 2017, 10am to 1pm

Venue: 261, Waterloo Centre, #03-21, Singapore 180261

O-Level Chemistry: Nitrogen Dioxide as an Air Pollutant

Being a Chemistry Trainer and also a fellow cyclists (yes guys, i love to cycle), i read this local Straits Times Newspaper article with interest.

Seems like our Nitrogen Dioxide, NO2(g) level within the lower atmosphere level is quite high in Singapore.

NO2(g) is considered a major air pollutant which has the following harmful effects:

1) Eye and lungs irritation and causes breathing difficulties

At high levels, it may even lead to inflammation of the lungs i.e. bronchitis

2) Acid rain consisting of Nitric Acid HNO3 that is highly corrosive

In the presence of oxygen in the air, nitrogen dioxide is converted to nitric acid via the following chemical equation:

4NO2(g) + 2H2O(l) + O2(g)  4HNO3(aq)

Nitric acid corrodes buildings and harms aquatic life and plants.

Do you know that due to acid rain, the Statue of Liberty in the United States of America had been badly corroded. In the year of 1983, the US Government launched a campaign to restore this historical figure of US Chemistry in action indeed!

NO2(g) is formed due to 2 main sources:

1) Lightning activities (which we have no control over since it is a natural source and it is NOT a daily source)

2) Vehicle exhaust fumes where high temperature around vehicles engine (which is a man-made source) causes 21% O2(g) and 78% N2(g) in the air to react to form oxides of nitrogen, NOx(g) which is mainly nitrogen monoxide, NO(g) and nitrogen dioxide, NO2(g).

Nitrogen reacts with oxygen at high temperature to form nitrogen monoxide or nitric oxide, NO(g).

N2(g) + O2(g)  2NO(g)

Nitrogen monoxide reacts with oxygen to form a brown colour gas called nitrogen dioxide, NO2(g).

2NO(g) + O2(g)  2NO2(g)

From the article, it shows that as concentration of air particulates (unburnt hydrocarbons) increases due to incomplete combustion of fossil fuels in vehicle exhaust fumes, there is also an increase in the concentration of nitrogen dioxide, NO2(g).

Since the satellites images have shown that the recent haze in Singapore is not from Indonesian fires (slash and burn method), it should be from the amounts of vehicle exhaust fumes produced locally on a daily basis.

  • More vehicles running on the roads
  • More incomplete combustion of fossil fuels
  • More unburnt hydrocarbons being produced
  • More nitrogen dioxide is also being produced
  • As such, the amount of unburnt hydrocarbons and the amount of nitrogen dioxides are highly correlated in a city which has a large number of vehicles running on the ground.

Time to ponder about if Singapore should encourage less driving….for our health and environment.

This is a good case study for GCE O-Level Pure Chemistry and Combine Science Chemistry students in Singapore to put their concepts learned in school into actual practice and application.

Same applies to Chemistry students worldwide doing other syllabus. This can be particularly severe in large cities, where traffic is heavy.

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.

Subscribe to my blog to receive 2 updates per month sent to your email!

PS: Under related articles below, there are several blog post discussions and questions related to Air & Atmosphere. You can also do a keyword search using the search box at the top right hand corner.