Answer
$9.297 \times 10^{-5} M$
Work Step by Step
1. Write the K formula:
$K = [Ca^{2+}][H{CO_3}^-][OH^-] = 8.037 \times 10^{-13}$
*The K value was calculated in 17.99b.
$[Ca^{2+}] = [H{CO_3}^-] = [OH^-] = x$
$8.037 \times 10^{-13} = [x][x][x] = x^3$
$x = \sqrt[3] {8.037 \times 10^{-13}}$
$x = 9.297 \times 10^{-5}$
