In a school chemistry experiment, when a strip of magnesium ribbon is burnt in air, which product is obtained as a white ash like powder?

Introduction / Context:
Many school chemistry experiments demonstrate how metals react with oxygen. Burning magnesium ribbon in air is a common activity in which students observe a bright white flame and then see a white ash like product. This question asks you to identify the chemical nature of that white residue. Recognising such basic reactions is essential for understanding metal oxides and combustion.

Given Data / Assumptions:

- The metal used is magnesium in the form of a ribbon.
- The ribbon is burnt in air, meaning it reacts mainly with oxygen gas.
- The observed product is a white ash like powder.
- Options are Baking soda, Calcium carbonate, White ash of magnesium oxide and Vinegar.

Concept / Approach:
When magnesium burns, it reacts vigorously with oxygen to form magnesium oxide. The word equation is magnesium plus oxygen gives magnesium oxide. The reaction produces a bright white light and leaves behind a white powder of magnesium oxide. Baking soda is sodium bicarbonate, calcium carbonate is found in limestone and chalk, and vinegar is a dilute solution of acetic acid. None of these are produced by simply burning magnesium in air. Therefore the correct description of the product is white ash of magnesium oxide.

Step-by-Step Solution:
Step 1: Recognise that burning magnesium involves a reaction between magnesium metal and oxygen from the air.Step 2: Recall the reaction: magnesium plus oxygen gives magnesium oxide as the product.Step 3: In the laboratory this magnesium oxide appears as a white ash like powder on the watch glass or tile.Step 4: Compare this with the options and identify that white ash of magnesium oxide correctly describes this product.Step 5: Confirm that baking soda, calcium carbonate and vinegar are unrelated substances not formed in this combustion reaction.

Verification / Alternative check:
You can verify by recalling the standard exercise where students write a balanced chemical equation for the burning of magnesium. Many textbooks explicitly state that the white powder obtained is magnesium oxide, which is a basic oxide and reacts with acids to form salts and water. No step in the experiment introduces sodium, calcium or acetic acid, so the other options are chemically inconsistent with the described setup.

Why Other Options Are Wrong:
Baking soda: This is sodium hydrogen carbonate and is commonly used in baking and cleaning. It cannot be formed by burning metallic magnesium in air.
Calcium carbonate: This compound is found in chalk, marble and shells. It requires calcium as a component and is not produced in a reaction involving only magnesium and oxygen.
Vinegar: Vinegar is a liquid containing acetic acid in water. Its appearance and composition are very different from a white ash solid, and it is not a combustion product of magnesium.

Common Pitfalls:
Some students may guess calcium carbonate or baking soda because they associate white powders with chalk or kitchen chemicals. However, the key is to focus on which elements are present in the reaction. Only magnesium and oxygen participate, so the product must contain these elements alone. Remembering that metal plus oxygen generally forms a metal oxide leads directly to magnesium oxide in this case.

Final Answer:
When magnesium is burnt in air, the white ash like product formed is Magnesium oxide.