Aluminium sulfate, Al2(SO4)3\text{Al}_2(\text{SO}_4)_3Al2(SO4)3, is widely used in water purification to coagulate impurities.
What is the relative formula mass (MrM_{\text{r}}Mr) of aluminium sulfate? (ArA_{\text{r}}Ar: Al=27\text{Al} = 27Al=27, S=32\text{S} = 32S=32, O=16\text{O} = 16O=16)
150150150
214214214
262262262
342342342