After heating washing soda, the colour of residue left behind would be

Options

A. Yellow
B. Black
C. Pink
D. White

Answer

To solve the question regarding the color of the residue left behind after heating washing soda, we can follow these steps:

### Step 1: Identify the chemical formula of washing soda.
Washing soda is chemically known as sodium carbonate decahydrate, and its formula is Na2CO3·10H2O.

**Hint:** Remember that washing soda contains water molecules in its structure.

### Step 2: Understand the process of heating washing soda.
When washing soda is heated, the water molecules (10H2O) evaporate due to the heat. This process is known as dehydration.

**Hint:** Think about what happens to water when it is heated—does it stay or does it change state?

### Step 3: Determine the product after heating.
After heating, the remaining substance is anhydrous sodium carbonate, which is represented by the formula Na2CO3.

**Hint:** Focus on what remains after the water has evaporated.

### Step 4: Identify the physical appearance of anhydrous sodium carbonate.
Anhydrous sodium carbonate (Na2CO3) is known to be a white powder.

**Hint:** Consider the typical colors associated with common chemical compounds—what color is sodium carbonate?

### Step 5: Conclude the answer.
Based on the above steps, the color of the residue left behind after heating washing soda is white.

**Final Answer:** D. White