V ( AlCl₃ ) = ?
M ( AlCl₃) = 0.2 M
V ( AgC₂H₃O₂) = 40 mL in liters : 40 / 1000 => 0.04 L
M ( AgC₂H₃O₂ ) = 0.5 M
number of moles ( AgC₂H₃O₂ ) :
n = M x V
n = 0.5 x 0.04
n = 0.02 moles
Mole ratio :
3 AgC₂H₃O₂(aq) + AlCl₃(aq) = 3 AgCl(s) + Al(C₂H₃O₂)₃(aq)
3 moles ---------- 1 moles
0.02 moles ------ ? ( moles AlCl₃)
moles AlCl₃ = 0.02 x 1 / 3
moles AlCl₃ = 0.02 / 3
= 0.0066 moles
V( AlCl₃) = n / M
0.2 = 0.0066 / V
V = 0.0066 / 0.2
V = 0.033 L or 33 mL
hope this helps!