Aula 15: Reatividade química dos metais (reações de deslocamento entre metais)

Summary

This video introduces an experimental chemistry lesson focused on metal reactivity and displacement reactions. The instructor, Luciano, explains the theory behind the reactivity of metals in a series of experiments. The lesson involves testing metal reactions with copper sulfate, sodium chloride solutions, hydrochloric acid, and water, evaluating the ability of metals to donate electrons and undergo oxidation. Students observe color changes, gas formation, and other signs of chemical reactions. The session also covers the importance of balancing chemical equations and understanding the reactivity series, concluding with a challenge to analyze specific reactions and their outcomes.

Takeaways

• 😀 The main focus of the experiment is on **metal reactivity** and **displacement reactions**, where less noble metals displace more noble ones.
• 😀 The **reactivity series** of metals ranks them by their tendency to lose electrons (electropositivity) or gain electrons (nobility).
• 😀 Less noble metals, such as zinc, have a higher tendency to lose electrons, making them more reactive than metals like copper.
• 😀 The reaction between metals and solutions, like copper sulfate or sodium chloride, allows us to observe whether displacement reactions occur.
• 😀 In the first experiment, **zinc** reacts with **copper sulfate**, displacing copper and forming **metallic copper**.
• 😀 **Reactions of metals with acids** like hydrochloric acid release hydrogen gas and form metal salts, with reactivity varying between metals.
• 😀 **Magnesium** reacts quickly with hydrochloric acid, while **copper** does not react, indicating a difference in reactivity.
• 😀 **Aluminum** reacts slowly with hydrochloric acid due to the formation of a protective oxide layer, preventing further reaction.
• 😀 The **reaction of metals with water** is tested with magnesium, which reacts to form magnesium hydroxide and hydrogen gas, while copper and aluminum do not react unless heated.
• 😀 In the reaction of **copper with nitric acid**, dangerous gases like nitrogen dioxide are formed along with copper nitrate, highlighting the importance of safety measures in such experiments.

Q & A

What is the main objective of the experimental chemistry class described in the transcript?

The main objective is to experimentally verify that less noble metals can displace more noble metals, balance chemical reactions, and observe visual evidence of the reactions such as color changes and gas formation.

How are metals classified in the context of the reactivity series, and what does this classification indicate?

Metals are classified based on their electropositivity and reactivity. Metals with higher reactivity can donate electrons more easily and are more likely to undergo oxidation, while those with lower reactivity act as oxidizing agents and tend to gain electrons.

What is the significance of the reactivity series in the reactions observed during the experiment?

The reactivity series indicates how different metals react with acids, salts, and water. Metals higher in the series, like magnesium and zinc, are more reactive and undergo reactions more readily, while metals lower in the series, like copper, are less reactive.

In the first part of the experiment, what was observed when zinc plates were placed in copper sulfate solution?

When zinc plates were placed in copper sulfate solution, the zinc became coated with a reddish-brown substance (copper metal), while the solution became colorless, indicating a displacement reaction where zinc displaced copper.

What happened when zinc was added to sodium chloride solution in the experiment?

No reaction occurred when zinc was added to sodium chloride solution because sodium, which is more reactive than zinc, does not undergo a displacement reaction under these conditions.

Why does aluminum not react quickly with water during the experiment?

Aluminum forms a protective oxide layer when exposed to water, which prevents further reaction. This oxide layer prevents the aluminum from reacting with water unless the layer is removed.

What was the reaction when magnesium metal was added to water?

Magnesium reacted with water, albeit slowly, producing a basic magnesium hydroxide solution and hydrogen gas, indicating a displacement of hydrogen from water.

What safety precautions are mentioned in the script for working with nitric acid during the experiment?

It is essential to use safety equipment such as goggles and gloves when working with nitric acid, and the procedure should be carried out in a fume hood due to the volatile gases produced. Direct contact with skin should be avoided, and if contact occurs, the area should be washed with water.

What is the result of the reaction between copper metal and concentrated nitric acid?

The reaction between copper metal and concentrated nitric acid produces a green solution due to the formation of copper nitrate, as well as brownish-red gas, which indicates the production of nitrogen oxides, which are harmful.

Why do certain metals not react with hydrochloric acid in the experiment, and how is this explained?

Some metals, like copper, do not react with hydrochloric acid because their reactivity is lower than that of hydrogen, meaning they cannot displace hydrogen ions from the acid.