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9.4. Preparation of Hydrogen
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Today, we will learn about the preparation of hydrogen in the laboratory. Can anyone tell me what happens when we react zinc with hydrochloric acid?
Does zinc react with hydrochloric acid to produce hydrogen gas?
That's correct! The equation for this reaction is Zn + 2HCl → ZnCl₂ + H₂↑. Zinc displaces hydrogen from the acid, generating hydrogen gas. Can anyone think of how we might collect this gas?
Maybe we can collect it in a balloon or a container?
Great suggestion! We actually use a method called downward displacement of water for collection since hydrogen is lighter than air and doesn't dissolve in water. Remember this: 'Water stays put; hydrogen rises up!'
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Now that we know how to prepare hydrogen, let's discuss safety. What precautions do we need to take?
We need to use dilute acid, right?
Exactly! Using dilute acid is crucial for safety. Starting the gas collection only after displacing all the air is also important. Can anyone explain why?
We want to avoid an explosion since hydrogen is flammable!
Yes! Hydrogen's flammability is a serious concern. Always remember: 'Safety first, or the flames burst!'
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Create a free accountLet’s dive deeper into the reaction process. Why does zinc displace hydrogen from hydrochloric acid?
I think because zinc is more reactive than hydrogen?
Exactly! Zinc's higher reactivity allows it to displace hydrogen. This is a great example of a single displacement reaction. Can anyone write the balanced equation for this reaction?
Zn + 2HCl → ZnCl₂ + H₂?
Perfect! Remember: 'Zinc knocks, hydrogen unlocks!' That's how we can remember this displacement.
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Create a free accountThink about how we could collect the hydrogen gas produced. What method did we discuss?
Downward displacement of water!
Exactly! Could you explain why this method works best for hydrogen?
Because hydrogen is lighter than air and doesn’t dissolve in water?
That's right! Always recall: 'Water's a trap, but hydrogen's a flap!' This will help remember the collection method.
Overview
Short Summary
This section discusses how hydrogen is prepared in the laboratory, focusing on the reaction of zinc with hydrochloric acid.
Medium Summary
The preparation of hydrogen can be accomplished in the laboratory by reacting zinc with dilute hydrochloric acid, resulting in the formation of zinc chloride and hydrogen gas. The hydrogen gas is collected using a method that utilizes its properties, specifically its insolubility in water and lighter density compared to air.
Reference YouTube Videos
Key Concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
Hydrogen Preparation: Hydrogen is prepared in the lab by reacting zinc with dilute hydrochloric acid.
Gas Collection: Hydrogen can be collected using the downward displacement of water due to its low density and insolubility.
Safety Precautions: Using dilute acid and starting gas collection only after air displacement are critical for safety.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
When zinc reacts with dilute hydrochloric acid, a bubbling reaction occurs, producing hydrogen gas which can be collected as described.
Hydrogen gas, produced in this manner, is often used in various laboratory experiments as well as industrial processes.
Memory Aids
Flash Cards
Glossary
Diatomic molecule
A molecule composed of two atoms, which can either be of the same or different chemical elements.
Downward displacement of water
A method used to collect gases that are less dense than water and do not dissolve in it.
Dilute acid
An acid that has been mixed with water to decrease its concentration, making it safer to handle.