Chemistry 9th Edition

According to the $law$ $of$ $conservation$ $of$ $mass$ $,$ mass of reactants = mass of products. In a chemical equation , the reactants are on the left hand side, and the products formed are on the right hand side. The reaction is: $Cr_{2}O_{3}$ + $2Al$ $\longrightarrow$ $2Cr$ + $Al_{2}O_{3}$ Thus the reactants are: $Cr_{2}O_{3}$ and $Al$. Thus by given data, mass of reactants = 34.0 g + 12.1 g = 46.1 g. And the products are $2Cr$ and $Al_{2}O_{3}$ By given data, mass of Chromium (Cr) = 23.3 g. Thus by the $law$ $of$ $conservation$ $of$ $mass$, 46.1 g = 23.3 g + Mass of $Al_{2}O_{3}$ Thus mass of $Al_{2}O_{3}$ = 46.1 - 23.3 = 22.8 g. Thus mass of Aluminum oxide ( $Al_{2}O_{3}$) produced = 22.8 grams