The balanced chemical equation between [tex] H_{3}PO_{4} and Ba(OH)_{2} [/tex] :
[tex] 2H_{3}PO_{4}(aq) + 3Ba(OH)_{2}(aq) -->Ba_{3}(PO_{4})_{2}(aq)+ 6H_{2}O(l) [/tex]
Moles of [tex] Ba(OH)_{2} =849 mL * \frac{1L}{1000mL} * \frac{0.128 mol}{L} = 0.108672 mol [/tex]
Moles of [tex] H_{3}PO_{4} [/tex] = [tex] 0.108672 mol Ba(OH)_{2} * \frac{ 2 molH_{3}PO_{4}}{3 mol Ba(OH)_{2}} = 0.072448 mol H_{3}PO_{4} [/tex]
Molarity of [tex] H_{3}PO_{4} = \frac{0.072448 mol}{(362 mL * \frac{1 L}{1000mL})}
= 0.200 M [/tex]
Correct answer is 0.200 M