Aluminium sulfate is widely used in water treatment as a coagulant to clarify drinking water by precipitating suspended impurities. What is the correct chemical formula of aluminium sulfate?
Al3(SO4)2\text{Al}_3(\text{SO}_4)_2Al3(SO4)2
Al2SO4\text{Al}_2\text{SO}_4Al2SO4
Al(SO4)3\text{Al}(\text{SO}_4)_3Al(SO4)3
Al2(SO4)3\text{Al}_2(\text{SO}_4)_3Al2(SO4)3