50 g of a substance is dissolved in 1 kg of water at $$+90^{\circ} \mathrm{C}$$. The temperature is reduced to $$+10^{\circ} \mathrm{C}$$. The density is increased from 1.1 to $$1.15 \mathrm{~g} \mathrm{~cc}^{-1}$$. What is the % change of molarity of the solution?

The empirical formula of calgon is

The statement related to law of definite proportions is

What are $$x$$ and $$y$$ in the following reaction?

$$x \mathrm{~Pb}_3 \mathrm{O}_4 \longrightarrow y \mathrm{PbO}+\mathrm{O}_2$$