Testing For Hydrogen, Oxygen, Carbon Dioxide & Chlorine | Matter | Chemistry | FuseSchool

FuseSchool - Global Education

10 Aug 201403:57

Summary

TLDRThis lesson teaches methods to identify common gases through laboratory testing. Hydrogen is confirmed by its squeaky pop sound when burned, indicating a combustion reaction with oxygen. Oxygen relights a glowing splint due to its higher concentration. Carbon dioxide extinguishes a lit splint and turns lime water milky, forming calcium carbonate. Ammonia turns damp red litmus paper blue and forms white ammonium chloride smoke with hydrochloric acid. Chlorine bleaches blue litmus paper red and white. These tests help distinguish gases that are otherwise colorless and odorless.

Takeaways

🔍 Gases like hydrogen, oxygen, carbon dioxide, ammonia, and chlorine cannot be identified by appearance alone due to their colorless and odorless nature.
🔥 To test for hydrogen, place a lit splint at the mouth of the reaction vessel to hear a 'squeaky pop', indicating its presence through combustion.
🌪️ A glowing splint will reignite in the presence of oxygen, which is a distinctive test for oxygen's presence in a reaction vessel.
💥 The 'squeaky pop' of hydrogen is due to a mini explosion caused by its high flammability and the combustion reaction with oxygen.
🌀 Carbon dioxide extinguishes a lit splint, but a more accurate test involves bubbling it through lime water, which turns milky due to calcium carbonate formation.
🌊 Ammonia extinguishes a lit splint and turns damp red litmus paper blue, indicating its presence through a chemical reaction.
🌫️ In the presence of concentrated hydrochloric acid, ammonia forms a white smoke of ammonium chloride, confirming its presence.
🔴 Chlorine turns damp blue litmus paper red and eventually bleaches it to white, a unique test for chlorine's presence.
🧪 Testing for gases in the laboratory is crucial because it is nearly impossible to determine a gas's identity by its appearance alone.
🌬️ The concentration of oxygen in a reaction vessel is higher than in air (21%), which is why a glowing splint relights in its presence.
📝 In conclusion, each gas has a unique test: hydrogen burns with a pop, oxygen reignites a glowing splint, carbon dioxide turns lime water milky, ammonia turns red litmus paper blue and forms ammonium chloride smoke, and chlorine bleaches blue litmus paper.

Q & A

Why is it difficult to identify a gas by its appearance alone?
-It is difficult because many gases, like hydrogen, oxygen, and carbon dioxide, are colorless and odorless, making them indistinguishable by sight or smell.
How can you confirm the presence of hydrogen in a reaction vessel?
-Place a lit splint at the mouth of the reaction vessel; a distinctive squeaky pop sound indicates the presence of hydrogen due to its combustion reaction with oxygen.
What property of hydrogen causes the squeaky pop sound when it burns?
-Hydrogen is highly flammable, and the pop sound is a result of a mini explosion caused by its rapid combustion in the presence of oxygen.
How do you test for the presence of oxygen in a reaction vessel?
-Place a glowing splint at the mouth of the reaction vessel; the splint will reignite in the presence of oxygen.
Why does a glowing splint reignite in the presence of oxygen?
-The glowing splint relights because the concentration of oxygen in the reaction vessel is higher than in air, which contains only 21% oxygen.
How can you differentiate between carbon dioxide and ammonia when both extinguish a lit splint?
-Bubble the gas through lime water (calcium hydroxide solution); carbon dioxide will turn the lime water milky due to the formation of calcium carbonate.
What happens when carbon dioxide is bubbled through lime water?
-Lime water turns milky in the presence of carbon dioxide because of the formation of calcium carbonate, which is a sign of carbon dioxide.
How does ammonia affect a damp red litmus paper?
-Ammonia turns damp red litmus paper blue, indicating its basic nature.
What reaction occurs when ammonia is exposed to concentrated hydrochloric acid?
-In the presence of concentrated hydrochloric acid, ammonia forms a white smoke of ammonium chloride, confirming its presence.
How can you test for the presence of chlorine gas?
-Chlorine gas turns damp blue litmus paper red and eventually bleaches it to white, indicating its presence.
What is the final conclusion of the lesson regarding the testing of different gases?
-The lesson concludes that hydrogen burns with a squeaky pop, oxygen relights a glowing splint, carbon dioxide turns lime water milky, ammonia turns damp red litmus paper blue and forms white smoke of ammonium chloride with concentrated hydrochloric acid, and chlorine turns damp blue litmus paper red and bleaches it to white.

Outlines

00:00

🔬 Laboratory Gas Testing Techniques

This paragraph introduces the necessity of gas testing in the laboratory due to the difficulty in identifying gases by appearance alone. It explains the colorless and odorless nature of gases like hydrogen, oxygen, and carbon dioxide, and the methods used to distinguish them. The paragraph details the testing process for hydrogen using a lit splint to produce a 'squeaky pop' sound, indicating the gas's presence through combustion. It also hints at the properties of hydrogen and oxygen that lead to these reactions, inviting the learner to reflect on why hydrogen burns with a pop and oxygen reignites a glowing splint.

Mindmap

Keywords

💡Hydrogen

Hydrogen is a chemical element with the symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe. In the context of the video, hydrogen is tested for its presence by its distinctive squeaky pop sound when a lit splint is placed at the mouth of a reaction vessel, indicating its flammability and the combustion reaction that produces water.

💡Oxygen

Oxygen is a chemical element with the symbol O and atomic number 8. It is essential for aerobic life and is a key component of the air we breathe, making up about 21% of the Earth's atmosphere. The video explains that oxygen can be identified by its ability to re-light a glowing splint, demonstrating its role in supporting combustion.

💡Carbon Dioxide

Carbon dioxide, with the chemical formula CO2, is a colorless, odorless gas that is produced by many biological processes and is a byproduct of combustion. The script describes a test for carbon dioxide using lime water, which turns milky due to the formation of calcium carbonate, indicating the presence of this gas.

💡Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a common gas in many household cleaning products and is also a significant component of the atmosphere of certain planets. The video mentions that ammonia extinguishes a lit splint and turns damp red litmus paper blue, which are characteristic reactions used to identify its presence.

💡Chlorine

Chlorine is a chemical element with the symbol Cl and atomic number 17. It is a yellow-green gas under standard conditions and is used in various disinfectants and industrial processes. The script explains that chlorine can be detected by its ability to turn damp blue litmus paper red and eventually bleach it to white, indicating a strong oxidizing property.

💡Combustion Reaction

A combustion reaction is a chemical reaction that occurs between a substance and an oxidant, typically producing heat and light. In the video, the combustion of hydrogen in the presence of oxygen is highlighted, producing a characteristic squeaky pop sound and water as the only product.

💡Lime Water

Lime water is an aqueous solution of calcium hydroxide, also known as slaked lime. It is used in various chemical tests, including the detection of carbon dioxide as described in the video, where it turns milky due to the formation of calcium carbonate.

💡Litmus Paper

Litmus paper is a type of paper that has been treated with litmus, a dye extracted from lichens, which is used as a pH indicator. In the script, red and blue litmus papers are mentioned as tools to test for ammonia and chlorine, respectively, by observing color changes.

💡Concentrated Hydrochloric Acid

Concentrated hydrochloric acid is a highly corrosive and strong mineral acid with the chemical formula HCl. The video script describes its use in testing for ammonia, where the presence of ammonia results in the formation of a white smoke of ammonium chloride.

💡Ammonium Chloride

Ammonium chloride is a compound with the formula NH4Cl, formed from the reaction of ammonia and hydrochloric acid. The script mentions the formation of a white smoke of ammonium chloride when ammonia is in the presence of concentrated hydrochloric acid, which is a test for the presence of ammonia.

💡Bleaching

Bleaching is the process of lightening or whitening a substance, often through oxidation. In the context of the video, chlorine's ability to bleach damp blue litmus paper to white is highlighted, demonstrating its strong oxidizing property.

Highlights

Identifying gases by appearance is nearly impossible due to similarities like colorlessness and odorlessness.

Hydrogen is tested by placing a lit splint at the reaction vessel's mouth, resulting in a distinctive squeaky pop.

The squeaky pop confirms hydrogen's presence due to its combustion in oxygen, producing water.

Oxygen is tested with a glowing splint that relights in its presence, indicating higher oxygen concentration.

Hydrogen's flammability causes a mini explosion, resulting in the pop sound when tested.

Carbon dioxide extinguishes a lit splint but can be accurately tested with lime water, turning it milky due to calcium carbonate formation.

Ammonia extinguishes a lit splint and turns damp red litmus paper blue.

Ammonia's presence is confirmed by the formation of white smoke of ammonium chloride when in contact with concentrated hydrochloric acid.

Chlorine turns damp blue litmus paper red and eventually bleaches it to white, indicating its presence.

Gases tested include hydrogen, oxygen, carbon dioxide, ammonia, and chlorine, each with specific reactions for identification.

The importance of accurate testing methods for gases in the laboratory due to their similar physical properties.

Hydrogen combustion in oxygen is a key test for its presence, demonstrated by a unique sound.

A glowing splint is used to test for oxygen, as it relights in an environment with higher oxygen levels.

Carbon dioxide's reaction with lime water is a classic test, showing a visual change to milky color.

Ammonia's effect on litmus paper provides a simple test for its presence, turning red paper blue.

The interaction between ammonia and concentrated hydrochloric acid produces a visible white smoke, confirming ammonia.

Chlorine's bleaching effect on blue litmus paper is a definitive test for its detection.

In conclusion, specific reactions for each gas provide clear methods for identification in a laboratory setting.