<span>I think it is the barometer and aneroid barometer</span>
The answer is (1) CaCO3. The bond between C and O is covalent bond. And the bond between Ca2+ and CO3 2- ion is the ionic bond. So the compound CaCO3 satisfy this condition.
The calculation of pH is based on the activity (aH) of hydrogen ions (H+) dissolved in solution. Specifically, the pH range of numbers is based on a logarithmic scale:
pH=-log (aH)
Log functions are used to rescale very large numbers (or very small numbers) into values much closer to 1. This is often done to deal with more reasonable
Numbers (for pH, 1 to 14). Mathematically, the negative sign in the formula means that pH must be less than 1.
The lower the number on the pH scale, the greater the concentration of hydrogen ions and the greater the material's acidity. The higher the number assigned on the pH scale, the greater the concentration of hydroxide ions and the more basic, or alkaline, the material.
The answer is 4.
