What are longitudinal waves? why are they called sound waves

Describe the chemical reaction based on the chemical equation below. also, explain whether the equation is balanced.

Ahypothrticalax type of ceramic material is known to have a density of 2.10 g/cm3 and a unit cell of cubic symmetry with a cell edge length of 0.57 nm. the atomic weights of the a and x elements are 28.5and 30.0 g/mol, respectively. on the basis of this information, which of the following crystal structures is (are) possible for this material: sodium chloride, cesium chloride, or zinc blende

How does kepler second law of planetary motion overthrow one of the basic beliefs of classical astronomy