Question

notice that "SO4" appears in two different places in the chemical equation SO-2>4 is a poyatomic ion called sulfate. what number should be placed in front of CaSO4 to give the same total number of sulfate ion in each side of the equation?

Answer 1

if you have the reaction equation like

CaSO₄ + AlCl₃→ CaCl₂ + Al₂(SO₄)₃

you have to balance the atoms, as per stachiomtery how many atoms required both sides sholud be equal

initial reaction CaSO₄ +AlCl₃ → CaCl₂ + Al₂(SO₄)₃

starting materials side Products side
Calcium no.s, Ca:1 Ca:1
Sulfur no.s, S: 1 S: 3
Oxygens no.s O: 4 O: 12
Aluminium no.s, Al: 1 Al: 2
Chlorine no.s, Cl 3 Cl: 2

So balance the atoms in equation both sides, add 3 to CaSO₄ to balance the sulfur_, in starting material side one, but product side three ) so the sufur will be both side same and it balance the oxygens also.( that multiplies also the oxygens 3 * 4= 12). then aluminium and chlorines add 3 to CaCl₂ now calcium atoms 3 set, but chlorine atoms multipleis from 2 to 6 so to balance add a 2 infront of the AlCl₃ .

after balancing the equation 3 CaSO₄ + 2 AlCl₃ → 3 CaCl₂ + Al2(SO₄)₃
Startin materials side Products side

Calcium no.s, Ca:3 Ca:3
Sulfur no.s, S: 3 S: 3
Oxygens no.s, O: 12 O: 12
Aluminium no.s, Al: 2 Al: 2
Chlorine no.s, Cl 6 Cl: 6

so balanced equation 3CaSO4 + 2 AlCl3→3 CaCl2 + Al2(SO4)3