A work-backwards-with-what-you're-given pH problem.104422

I've posted a few times before and have gotten really great results thanks to OTA #104422...but this one (and a bunch like it) are killing me slowly. I need to SEE how it's done. Calculate the pH of CO2-saturated water at 25 degrees C, given that the CO2 concentration in air is 320 and that for carbon dioxide the Henry's Law constant KH=3.4E-2 mol L-1 atm-1 at 25 degrees C. Furthermore, the ionization constant, Ka, for H2CO3 has a value of 4.5E-7 mol L-1 at this temperature.

Another work-backwards-to-get-the-answer problem?

**Assume that a waste contains 340.0 mg/L of biodegradable CH2O and is processed through a 200000.0 L/day sewage treatment plant which converts 40% of the waste to CO2 and H2O. Calculate the volume of air (at 25 degrees, 1 atm) required for this conversion. Assume that the O2 is transferred to the water with 20% efficiency**

I'm really lost, I'd like to see how its done, I have approx. 15 more to do.

What is the fraction of NTA present after HT2- has been brought to equilibrium with solid PbCO3 at pH 7.00, in a medium in which [HCO3-] = 2.00E-3 M?

Converting and calculating percentages . Again, I just need to see ONE of these (hopefully)!!

Assume that the wet limestone process requires 1 metric ton of calcium carbonate to remove + 85.0 % of the sulfur from 4 metric tons of coal containing + 10.0 % S Assume that the sulfur product is calcium sulfate. Calculate the percentage of the limestone converted to calcium sulfate.

Another work-backwards-to-get-the-answer problem - FOR OTA 104422

THIS IS FOR OTA 104422 (Note: This question was posted once already and the response received was incorrect. Thus, it is being reposted SPECIFICALLY for OTA 104422) The questions/assignments are coming faster than I can complete them! I'm going to try and post a series of questions that are NOT related in content (I'm hoping to get enough *different* ones worked out so I can use them as a guide to complete the others). Ewen, thanks again for all your help. Your step by step instructions are PRICELESS!! Here's the new one (and thankfully there are only about 8 of these for me to do): **Assume that a waste contains 340.0 mg/L of biodegradable CH2O and is processed through a 200000.0 ... click for more