Answer is: 2 mole of calcium chloride will react will react with sodium hydroxide.
Chemical reaction: CaCl₂ + 2NaOH → Ca(OH)₂ + 2NaCl.
n(NaOH) = 4 mol.
n(CaCl₂) = ?
From chemical reaction: n(CaCl₂) : n(NaOH) = 1 : 2.
n(CaCl₂) : 4 mol = 1 : 2.
n(CaCl₂) = 4 mol ÷ 2.
n(CaCl₂) = 2 mol.