Author Question: An industrial plant processes its waste water through a sedimentation tank that removes hazardous ... (Read 62 times)

Mimi · **on:** Aug 23, 2018

An industrial plant processes its waste water through a sedimentation tank that removes hazardous metals by precipitating them as insoluble carbonate salts. If sodium carbonate is gradually added to the tank, what would be the order of precipitation of the metals, Pb²⁺, Cu²⁺, Hg₂²⁺, and Zn²⁺ if each is 1.0 10⁴ M? ( K_sp PbCO₃ = 7.4 10¹⁴, K_sp CuCO₃ = 1.4 10¹⁰, K_sp Hg₂CO₃ = 8.9 10¹⁷, and K_sp ZnCO₃ = 1.4 10¹¹)

a.
Pb²⁺, Hg₂²⁺, Zn²⁺, Cu²⁺

b.
Hg₂²⁺, Pb²⁺, Zn²⁺, Cu²⁺

c.
Cu²⁺, Zn²⁺, Pb²⁺, Hg₂²⁺

d.
Cu²⁺, Zn²⁺, Hg₂²⁺, Pb²⁺

e.
All metal ions will precipitate at the same time.

Question 2

A solution is 0.010 M in each of Pb(NO₃)₂, Mn(NO₃)₂, and Zn(NO₃)₂. Solid NaOH is added until the pH of the solution is 8.50. Which of the following statements is true?
Salt
K_sp
Pb(OH)₂
1.4 10²⁰
Mn(OH)₂
2.0 10¹³
Zn(OH)₂
2.1 10¹⁶

a.
No precipitate will form.

b.
Only Pb(OH)₂ will precipitate.

c.
Only Mn(OH)₂ will precipitate.

d.
Only Zn(OH)₂ and Pb(OH)₂ will precipitate.

e.
All three hydroxides will precipitate.