Lithium oxide is used to remove water from air according to the reaction,

${\mathrm{Li}}_2\mathrm{O}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)⟶2\mathrm{LiOH}\left(\mathrm{s}\right)$

If $72 \mathrm{kg}$ of water is to be removed and $35 \mathrm{kg}$ of ${\mathrm{Li}}_2\mathrm{O}$ is available, then how many $\mathrm{kg}$ of excess reactant is left?

Weighing $3104$ carats $(1 \mathrm{carat}=200 \mathrm{mg})$ , the Cullinan diamond was the largest natural diamond ever found. How many carbon atoms were present in the stone?

Calculate the percentage by mass of chromium in each of the following oxides.

${\mathrm{Cr}}_2{\mathrm{O}}_3$

Calculate the percentage by mass of chromium in each of the following oxides.

${\mathrm{CrO}}_3$