Empirical Formula of Magnesium Oxide

Summary

In this demonstration, the speaker shows how to create magnesium oxide by burning magnesium. After explaining magnesium's reactive properties and weighing it in a crucible, the speaker ignites it using a Bunsen burner. As the magnesium reacts with oxygen, it forms magnesium oxide, which is visibly different from the original metallic form. The experiment highlights how mass increases due to the added oxygen. The speaker concludes by explaining that the empirical formula for the compound can be determined by calculating the mass of the elements involved. In the next episode, the speaker promises to explain how to derive the formula.

Takeaways

• 🔥 The video demonstrates how to make magnesium oxide from its elements using fire.
• 🧪 Magnesium is a metallic element, number 12 on the periodic table, and is reactive, so it's stored in plastic bags.
• ⚖️ The weight of the crucible with the lid is measured before and after adding magnesium to determine the exact mass of magnesium used.
• 🔥 The magnesium is heated in a crucible using a Bunsen burner, with the hottest part of the flame being at the tip of the blue cone.
• ✨ The reaction between magnesium and oxygen produces a bright light and energy release as the magnesium burns.
• 🌬️ The cap is placed on the crucible briefly to trap smoke while still allowing oxygen circulation for the reaction to continue.
• 💧 Water is added after the initial heating to ensure that all magnesium reacts, and the crucible is reheated for completion.
• 🔬 The video explains how empirical formulas can be determined by knowing the masses of the elements involved in a compound.
• 🧮 The final mass of the crucible increases because burning adds oxygen to the magnesium, creating solid magnesium oxide.
• 📊 The process leads to understanding how chemists determine the chemical formula of a compound by using mass data.

Q & A

What is the purpose of the demonstration in the video?

The purpose of the demonstration is to show how to make magnesium oxide from its elements, specifically by burning magnesium metal in the presence of oxygen.

Why is magnesium typically kept in plastic bags?

Magnesium is usually kept in plastic bags because it is a reactive element that will react with the air if left exposed.

What is the significance of measuring the mass of the crucible and lid before adding the magnesium?

Measuring the mass of the crucible and lid before adding magnesium allows the experimenter to determine the exact mass of the magnesium by subtracting the initial weight from the total weight after adding the magnesium.

Why does the instructor wrap the magnesium into a loose ball?

The magnesium is wrapped into a loose ball so that it can fit into the crucible and allow enough surface area for it to react with oxygen during the burning process.

Where is the hottest part of the flame in a Bunsen burner, and why is this important?

The hottest part of the flame in a Bunsen burner is at the tip of the small blue cone. This is important because placing the crucible at this point ensures the magnesium is heated to the right temperature for it to react with oxygen.

Why does the experimenter partially cover the crucible during the reaction?

The experimenter partially covers the crucible to trap some of the smoke (magnesium oxide) inside while still allowing oxygen to circulate to continue the reaction.

Why does the instructor add water to the product after burning?

Water is added as a concentrated source of extra oxygen to ensure that all the magnesium has reacted, ensuring a complete conversion to magnesium oxide.

What happens to the magnesium after the burning process?

After the burning process, the shiny, silvery magnesium strip is transformed into a white powder, which is magnesium oxide.

Why does the mass of the crucible increase after burning the magnesium?

The mass of the crucible increases because oxygen from the air has combined with the magnesium to form magnesium oxide, a solid product, which adds mass to the container.

What is an empirical formula, and how can it be determined in this experiment?

An empirical formula shows the lowest whole number ratio of the elements in a compound. It can be determined in this experiment by knowing the masses of magnesium and oxygen and then calculating the ratio between them based on their atomic weights.