A rock sample is suspected to be pure magnesium sulfate (MgSO₄). It is pulverized and subjected to elemental analysis. The results revealed that the sample contains 21.45% Mg, 28.52% S, and 50.85% O. Is the sample of rock pure MgSO₄?

Adam's catalyst, MO₂, is used widely as a catalyst in organic synthesis reactions. Given that MO₂ contains 14.1% oxygen by mass, determine the identity of M. 

An oxide of chlorine with a partial molecular formula of Cl₂O_x is analyzed. If the result showed that the compound contains 38.76% chlorine by mass, determine the value of x.

The empirical formula of a compound is PCl₅ and it has a molar mass of 416.48 g/mol. Calculate the molecular formula.

Analysis of a compound shows that the compound contains twelve times as much carbon as hydrogen by mass. If the compound only contains carbon, hydrogen, bromine and oxygen, determine its molecular formula. Molar mass = 161 g/mol.

Consider the diagram below that illustrates an ionic compound. The cations are represented by light green spheres and the anions are represented by purple spheres. Choose among the following compounds that match the given illustration: Al₂(C₂O₄)₃, Ba(CH₃COO)₂, RbCl, Na₂Cr₂O₇.

A 3D model of a compound is shown below. White spheres represent H, grey represents C, red represents O and blue represents N. Identify its molecular and structural formula.