Mujhe chemistry ka enthalpy Kay topic par bilkul teacher ki Tarah examples important things Kay sath samjhao in roman Urdu

Enthalpy (symbol: H) kisi chemical system ki total heat content hoti hai. Ismein system ki internal energy aur pressure-volume work shamil hota hai. Hum H ko directly measure nahi kar sakte, lekin hum ismein hone wale change ko measure karte hain.

Jab koi chemical reaction hota hai, to usmein heat ya to absorb hoti hai ya release hoti hai. Is heat change ko change in enthalpy (ΔH) kehte hain, jab reaction constant pressure par ho.
Formula:
ΔH = H(products) - H(reactants)
Iska unit kilojoules per mole (kJ/mol) hota hai.

Ye wo reactions hain jinmein heat release hoti hai system se surroundings mein. Is wajah se surroundings ka temperature badh jata hai.

• In reactions ke liye ΔH ki value negative hoti hai (ΔH < 0).
• Example: Methane ka jalna (combustion). CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) + Heat Is reaction mein heat bahar nikalti hai, isliye iska ΔH negative hoga.

Ye wo reactions hain jinmein heat absorb hoti hai surroundings se system mein. Is wajah se surroundings ka temperature kam ho jata hai (thanda mehsoos hota hai).

• In reactions ke liye ΔH ki value positive hoti hai (ΔH > 0).
• Example: Photosynthesis. 6CO₂(g) + 6H₂O(l) + Heat → C₆H₁₂O₆(s) + 6O₂(g) Is reaction mein plants sunlight se heat energy absorb karte hain, isliye iska ΔH positive hoga.

• State Function: Enthalpy ek state function hai. Iska matlab hai ki ΔH ki value sirf reaction ki initial aur final state par depend karti hai, na ki us path par jisse reaction hua hai.
• Constant Pressure: ΔH ki measurement hamesha constant pressure par ki jaati hai.
• Stoichiometry: ΔH ki value reaction ki stoichiometry (reactants aur products ke moles) par depend karti hai. Agar reaction ko reverse kiya jaye, to ΔH ka sign change ho jata hai. Agar reaction ke coefficients double kiye jayen, to ΔH ki value bhi double ho jati hai.