Question

From where did these water droplets appear ? Explain.

Answer 1

Step 1: Identify the compound being heated:
The compound is ferrous sulphate crystals, chemical formula: \[ \text{FeSO}_4·7\text{H}_2\text{O} \] Each ferrous sulphate molecule contains 7 water molecules, termed water of crystallization.

Step 2: What happens during heating:
- Heating ferrous sulphate crystals releases the water of crystallization as water vapor.
- The reaction is:
\[ \text{FeSO}_4·7\text{H}_2\text{O} \xrightarrow{\text{Heat}} \text{FeSO}_4 + 7\text{H}_2\text{O} \]

Step 3: Formation of water droplets:
- The released water vapor ascends the test tube.
- It contacts the cooler upper sections of the tube.
- Cooling causes the water vapor to condense into visible water droplets.

Step 4: Conclusion:
Water droplets observed during the heating of ferrous sulphate crystals result from the evaporation of water of crystallization, which subsequently condenses on the cooler inner walls of the tube.

Answer 2

Step 1: Compound Identification:
The substance under examination is ferrous sulphate crystals, with the chemical formula
\[\text{FeSO}_4·7\text{H}_2\text{O}\]
This signifies its hydrated form, containing water of crystallization.

Step 2: Initial Color Observation:
- FeSO₄·7H₂O crystals are typically light green.
- This coloration is attributed to the presence of seven water molecules bound to each ferrous sulphate molecule.

Step 3: Heating Process:
- Upon heating, the crystals release their water of crystallization.
- The corresponding chemical reaction is:
\[\text{FeSO}_4·7\text{H}_2\text{O} \xrightarrow{\text{Heat}} \text{FeSO}_4 + 7\text{H}_2\text{O}\]
- As water evaporates, a color alteration occurs.

Step 4: Post-Heating Observation:
- The resulting solid is anhydrous ferrous sulphate, which is white or colorless.

Step 5: Summary of Change:
- The color transformation upon heating is:
Green → White
This change is a direct consequence of the hydrated green crystals losing their water molecules and becoming a white anhydrous powder.

Answer 3

Step 1: Definition of Water of Crystallization:
- Water of crystallization refers to a specific quantity of water molecules that are chemically integrated into a compound's crystal lattice.
- These molecules are integral to the compound's crystalline structure and physical attributes.

Step 2: Illustration with Ferrous Sulphate:
- A single molecule of ferrous sulphate incorporates 7 water molecules as water of crystallization.
- Its chemical representation is: FeSO₄·7H₂O
- This specific compound is designated as hydrated ferrous sulphate.

Step 3: Molecular Formulas of Other Crystalline Salts:
(I) Copper Sulphate:
- Contains 5 water molecules of crystallization.
- Chemical formula: CuSO₄·5H₂O

(II) Sodium Carbonate:
- Contains 10 water molecules of crystallization.
- Chemical formula: Na₂CO₃·10H₂O

Step 4: Summary:
The crystalline formulations of the mentioned salts are:
- Ferrous sulphate: FeSO₄·7H₂O
- Copper sulphate: CuSO₄·5H₂O
- Sodium carbonate: Na₂CO₃·10H₂O
These associated water molecules are responsible for the distinct crystalline forms and coloration of these compounds.

Answer 4

Stage 1: Source Material - Gypsum:
- Gypsum is a naturally occurring mineral, chemically denoted as CaSO₄·2H₂O (calcium sulfate dihydrate).
- It inherently contains two water molecules per formula unit, known as water of crystallization.

Stage 2: Formation of Plaster of Paris from Gypsum:
- Upon heating gypsum to 373 K (or 100°C), water molecules are expelled.
- The chemical transformation is represented as:
\[ \text{CaSO}_4·2\text{H}_2\text{O} \xrightarrow{373\,\text{K}} \text{CaSO}_4·\tfrac{1}{2}\text{H}_2\text{O} + \tfrac{3}{2}\text{H}_2\text{O} \]
- The resultant compound is identified as Plaster of Paris (CaSO₄·½H₂O).

Stage 3: Characteristics of Plaster of Paris:
- It presents as a white powder.
- When hydrated with water, it solidifies into a rigid mass through rehydration, reverting to gypsum.

Stage 4: Applications of Plaster of Paris:
1. Medical Applications: Utilized in the fabrication of supports for fractured bones due to its rapid setting and firm structural integrity.
2. Decorative Applications: Extensively employed in the creation of ornamental items, including statuary, architectural designs, and suspended ceilings.

Stage 5: Summary:
- Plaster of Paris (CaSO₄·½H₂O) is synthesized by heating gypsum at 373 K.
- Its primary uses include orthopedic casts and interior decorative elements.