Answer:
1.9 x 10⁻¹³M
Step-by-step explanation:
Given 0.027M Ca(OH)₂(aq) => 0.027M Ca⁺²(aq) + 2(0.027M) OH⁻(aq)
2(0.027M) OH⁻(aq) = 0.054M OH⁻(aq).
from [H⁺][OH⁻] = 1 x 10⁻¹⁴ at STP Conditions (0°C, 1Atm)
∴{H⁺] = [H₃O⁺] = (1 x 10⁻¹⁴/0.054)M = 1.85 x 10⁻¹³M or 1.9 x 10⁻¹³at 0°C & 1Atm pressure.