Identify 'x', 'y' and 'z' in the following reaction: $2\mathrm{KClO}_{3}(x)\xrightarrow{(y)}\mathrm{2KCl}(x)+\mathrm{O}_{2}(z)$

In a chemical equation, the physical states of reactants and products are represented in parentheses immediately following their chemical formulae, such as $(s)$ for solid, $(l)$ for liquid, $(g)$ for gas, and $(aq)$ for aqueous solution. Therefore, $x$ represents the physical state of $\mathrm{KClO}_3$ and $\mathrm{KCl}$ (which is solid, 's'), and $z$ represents the physical state of $\mathrm{O}_2$ (which is gas, 'g'). Reaction conditions such as temperature, pressure, or catalyst are written above and/or below the reaction arrow, which is represented by $y$. Thus, option (d) is correct.

• Why other options are incorrect:
• Option (a) is incorrect because $x$ represents the physical state of $\mathrm{KClO}_3$ and $\mathrm{KCl}$, which are solids, not gases.
• Option (b) is incorrect because $y$ represents the reaction condition (such as heat or catalyst), not a physical state like liquid.
• Option (c) is incorrect because $x$ and $z$ represent physical states, not the number of moles or molecules.