Question 7 What is the solubility of Al 3+ at pH = 4.45 if solubility is limited

ID: 836305 • Letter: Q

Question

Question 7

What is the solubility of Al3+ at pH = 4.45 if solubility is limited by formation of the hydroxide? (Ksp Al(OH)3 = 3.1 x 10-34, Kw = 1.0 x 10-14)

3.8 x 10-9 M

0.042 M

6.4 x 10-3 M

3.1 x 10-34 M

1.4 x 10-5 M

1 points

Question 8

Which of the following statements is not true?

Chemical oxygen demand values are typically higher than biological oxygen demand values for the same sample.

Fe2+ is significantly more soluble in water than Fe3+

In O2-saturated water, the reduction of O2 to water is the half-reaction that dominates pE.

Water hardness is a measure of the concentration of calcium and magnesium ions in solution

Water in equilibrium with CO2 but not CaCO3 is expected to have an alkaline pH

3.8 x 10-9 M

0.042 M

6.4 x 10-3 M

3.1 x 10-34 M

1.4 x 10-5 M

pH = 4.45 , pOH = 14-4.45 =9.55 ,, [OH-] = 10^-9.55 = 2.8184 x 10^-10

Ksp = 3.1 x 10^-34 = [Al3+][OH-]^3

3.1 x 10^-34 = [Al3+][2.8184 x 10^-10) ^3

[Al3+] = 1.384 x 10^-5 M = 1.4 x 10^-5 M ( rounded value)

2) Fe2+ is more solube in water than Fe3+ statement is wrong since Fe3+ forms more soluble hydroxide compared to Fe2+ hydroxide.

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.