Atomic reaction is nothing but the reaction of one atom with the other atom to form the new compound.
<u>Explanation:</u>
- The atom is considered as the ultimate basic particle of the matter.
- This atom comprise of electron neutrons and protons.
- Generally in the atomic reaction, there will be loss or gain of the electron to or from the substance with which the reaction takes place.
- In default, all atoms wanted to attain the noble gas configuration which is stable in nature. These atoms from the ionic or covalent bond by sharing the electron.
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Answer:
C) 
Explanation:
pH is defined as the negative logarithm of the concentration of hydrogen ions.
Thus,
pH = - log [H⁺]
The expression of the pH of the calculation of weak acid is:-
Where, C is the concentration = 0.5 M
Given, pH = 2.94
Moles = 0.100 moles
Volume = 1.00 L
So, 
C = 0.100 M



A compass needle points north because the north pole of the magnet inside it is attracted to the south pole of Earth's built-in magnet . <u><em>And irons are heavily attracked to magnet</em></u> .So this is why iron needles used in compasses .