SCUBA stands for Self Contained Underwater Breathing Apparatus. It is used for breathing underwater.
Pure mixture of 50% both is dangerous.
Normal ratio of both is not used for deep depth.
Maximum Helium as 96% is used in deep dive to prevent from Nitrogen Narcosis.
Too much Oxygen is dangerous.

Kw is ionic product of water.
Kw tells us about strength of water in making H+ and OH-.
H+ makes water acidic and HO- makes water basic.
Pure water has equal amount of H+ and HO-.

An electrochemical cell that converts chemical energy into electrical energy by a spontaneous redox reaction.
Lead storage battery works on spontaneous redox reactions.
Voltaic cell is also called Galvanic cell.

Enthalpy of combustion releases heat and exothermic.
Enthalpy of solution can be positive or negative depends on the substance.
Enthalpy of reaction it also be negative or positive.
Enthalpy of atomization is always positive because energy is required to break bonds and form free atoms.

Potential energy is due to position.
Electric energy is due to electric current.
Total energy of system consist of K.E and P.E which is called Internal Energy.
Kinetic energy is due to motion.

Zinc protects iron / steel from rusting by forming a protective coating.

The unit of rate constant k depends on the order of the reaction.

Primary cell in not rechargeable. It is also called Galvanic cell.
Secondary cell is rechargeable. It is also known as Accumulator.

مثال کے طور پر جب ہم پانی کو اُبالتے ہیں تو پانی 100 سینٹی گریڈ پر اُبلتا ہے۔
پانی کے اُبلنے کے دوران پانی پر ہوا کا دباؤ / پریشر ہوتا ہے۔اگر ہم پانی کے اوپر سے ہوا کے دباؤ کو ویکیوم پمپ کی مدد سے کم کر دیں تو یہی پانی 100 سینٹی گریڈ کی بجائے کم درجہ حرارت پر بھی آسانی سے اُبل سکے گا