Gypsum on heating above 437 gives

Options

A. `CaSO_4.(5)H_2O`
B. `CaSO_4.H_2O`
C. `CaO+SO_3`
D. `CaSO_4`

Answer

To solve the question regarding what gypsum produces when heated above 437 K, we can follow these steps:

### Step 1: Identify the chemical formula of gypsum
Gypsum is a hydrated mineral, and its chemical formula is:
\[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \]

### Step 2: Understand the heating process
When gypsum is heated, especially at temperatures above 437 K (which is approximately 164 °C), the water of crystallization (the water molecules that are part of the crystal structure) begins to evaporate.

### Step 3: Write the thermal decomposition reaction
When gypsum is heated, the following reaction occurs:
\[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \xrightarrow{\text{heat}} \text{CaSO}_4 + 2\text{H}_2\text{O} \]

This means that upon heating, gypsum loses its water of crystallization and transforms into anhydrous calcium sulfate.

### Step 4: Identify the product
After heating gypsum above 437 K, the product obtained is:
\[ \text{CaSO}_4 \]
This is known as anhydrous calcium sulfate.

### Final Answer
Gypsum on heating above 437 K gives:
\[ \text{CaSO}_4 \]

---