Answer to Question #286890 in Chemistry for michelle

Question

In a saturated solution of Al(OH)₃, the concentration of OH⁻ is 2.6 x 10⁻⁵ mol/L. The concentration of Al³⁺ in mol/ L is which of the following?

1. 7.8 x 10⁻⁵
2. 8.7 x 10⁻⁶
3. 7.8 x 10⁻¹⁵
4. 2.6 x 10⁻⁵
5. 5.2 x 10⁻⁵

Answer 1

Solution:

Al(OH)₃(s) ⇌ Al³⁺(aq) + 3OH⁻(aq)

___S_________S__________3S_____

According to the equation above:

[OH⁻] = 3S = 2.6×10⁻⁵ mol/L

Hence,

[Al³⁺] = S = [OH⁻] / 3 = (2.6×10⁻⁵ mol/L) / 3 = 8.667×10⁻⁶ mol/L = 8.7×10⁻⁶ mol/L

[Al³⁺] = 8.7×10⁻⁶ mol/L

Answer: 2. 8.7×10⁻⁶