[hiddengems]

Hi,

I'm having problems with my homework and calculation. Our professor talks too fast and most of the people in my class are engineers whereas me in a science major so.. It's hard for me to understand these ... Could anyone help me pls???

1) From each of the following values of water solubility, evaluate the corresponding solubility product constant:

a) FeS 6.3x10^-9 mol/L

b) Mg3 (PO4)2 6.1x10^10-5mol/L

2) Using half reactions, write complete balanced oxidation-reduction equations for the following:

a) OXidation of NH4+ to NO2-

Reduction of O2 to H2O

B) Oxidation of C6H12O6 to CO2

Reduction of Cr2O72- to Cr3+

3) A metal plating waste contains 20mg/L Cu2+ and it is desired to add Ca (OH)2 to precipitate all but 0.5g mg/L of the copper. To what concentration in moles per liter must the hydroxide concentration be raised to accomplish this?

4) It is desired to flouridate a water supply by adding sufficient NaF to increase the fluoride concentration to 1mg/L. Will this flouride concentration be soluble in a water supply containing 200mg/L of calcium? Show your computations.

5) Equilibrium constants for the complexs between cadmium (II) and choloride are K1=21, K2=8, K3=1.2 and K4=0.35. Calculate the molar concentration of each of the first four cadium choloride complexes in a water sample if Cd2+=10^-8M and CI-=10^-3. Identify the most prevalent cadmium species.

6) a) Using standard free energies of formation, calculate Ksp for CaCO3 (c) at 25c

b) If a water is in equilibrium with CaCO3 (c) at a 25c, what is the Ca2+ concentration in mg/L if the CO3^2- concentration is 5mg/L?

c) Calculate Ksp for a temperature of 16c, which is typical of many groundwaters

d) A sample of groundwater at 16c has 100mg/L of Ca^2+ and 10mg/LCO3^2-. Is this water in equilibrium with CaCO3 (c)?. If not, is CaCO3 (c) dissolving or precipitating?

hidden gems

[Borek]

You have to show your attempts at solving the question to receive help. This is a forum policy.

For sure you at least know what solubility product is. How does it look for FeS? How is concentration of Fe^2- related to the solubility? Of S^2-?