Answer is: 0.102 moles of HCl would react.
Balanced chemical reaction:
2HCl(aq) + Sr(OH)₂ → SrCl₂(aq) + 2H₂O(l).
V(Sr(OH)₂) = 37.1 mL ÷ 1000 mL/L.
V(Sr(OH)₂) = 0.0371 L; volume of the strontium hydroxide solution.
c(Sr(OH)₂) = 0.138 M; molarity of the strontium hydroxide solution.
n(Sr(OH)₂) = c(Sr(OH)₂) · V(Sr(OH)₂).
n(Sr(OH)₂) = 0.0371 L · 0.138 mol/L.
n(Sr(OH)₂) = 0.0051 mol; amount of the strontium hydroxide.
From balanced chemical reaction: n(Sr(OH)₂) : n(HCl) = 1 : 2.
n(HCl) = 2 · n(Sr(OH)₂).
n(HCl) = 2 · 0.0051 mol.
n(HCl) = 0.0102 mol; amount of the hydrochloric acid.