Ammonium dichromate, $(\text{NH}_4)_2\text{Cr}_2\text{O}_7$, decomposes on heating to nitrogen, chromium(III) oxide and steam. What mass of solid $\text{Cr}_2\text{O}_3$ is left when $75.6\ \text{g}$ of it is heated until it stops changing? The molar masses are $252\ \text{g/mol}$ for the dichromate and $152\ \text{g/mol}$ for $\text{Cr}_2\text{O}_3$.