Some Basic Conc...

What is the percent $$X$$ by mass for compound $$XY_{2}$$ if compound $$XY$$ is $$74$$% $$X$$ by mass?

Who arranged elements his periodic table, based upon atomic weight:

Spectroscopy is :

A student carries out the following reaction in the laboratory:

The reaction between dinitrogen monoxide, $$N_{2}O$$ and oxygen gas, $$O_{2}$$, carried out at high pressures, results in the formation of dinitrogen tetroxide, $$N_{2}O_{4}$$, as the only product. The unbalanced equation for the reaction is:

Consider the four decompositions shown here:
Reaction I: $$Ca(NO_{3})_{2}(s)\xrightarrow {\Delta} CaO(s) + N_{2}O_{5}(g)$$
Reaction II: $$CaSO_{3}(s) \xrightarrow {\Delta} CaO(s) + SO_{2}(g)$$
Reaction III: $$Ca(ClO_{3})_{2}(s) \xrightarrow {\Delta} CaCl_{2}(s) + 3O_{2}(g)$$
Reaction IV: $$CaCO_{3}(s) \xrightarrow {\Delta} CaO(s) + CO_{2}(g)$$
In each case, a solid compound of calcium undergoes thermal decomposition, producing a gaseous product and a calcium containing residual solid.
Assuming equal masses of the four compounds, $$Ca(NO_{3})_{2}, CaSO_{3}, Ca(ClO_{3})_{2}$$, and $$CaCO_{3}$$, are heated in open containers to constant mass, in which case will the mass of solid in the container change by the smallest percentage?

Atom is the word derived from the Greek word atomio, which means:

A 5% by mass of an aqueous solution of $$A$$ of molar mass 342 g mol$$^{-1}$$ is isotonic with 0.878% by mass of an aqueous solution of another substance B. The molar mass of $$B$$ in g mol$$^{-1}$$ is:

Who proposed that equal volumes of gases at the same temperature and pressure have  same number of molecules.

Which one of the following statements is false?