Env. Chem ? re: masses, ppm, and room dimensions

The computer allows 12 tries on any question and I've already exhausted 3 tries. Can someone show this to me, step-by-step? I have only 4 others like it, but my math skills are holding me back.***** What mass of formaldehyde gas (in grams) must be released from building materials, carpets, etc. in order to produce a concentration of 0.50 ppm of the gas in a room having dimensions of 4.0m X 5.0m X 1.0m?****the computer offered the hint: Calculate vol of room in cubic meters and convert to liters. Use ideal gas law and concentration to calculate amount of formaldehyde. (but I thought I did that!

Bond energy

(5) The lowest energy photon which is able to split an oxygen molecule has a wavelength of 280.0 nm. Based on this, what is the bond energy of the oxygen molecule in kJ/mol?

These are killing me. #104422 has had the most luck, but I need help!! Anyone?

(7) The Arrhenius equation (see your introductory chemistry textbook) relates reaction rates to temperature via the activation energy. Calculate the ratio of the rates at -30 degrees C (a typical stratospheric temperature) for two biomolecular reactions having the same Arrhenius A factor and initial concentrations , one of which is endothermic and has an activation energy of 54000 J /(mol) and the other of which is exothermic and has an activation energy of 7000 J /(mol).

For OTA #104422 or #103846

Please only respond if you are 100% sure as this question has already been posted once. (10) The threshold/NOEL level found for a particular chemical from animal studies is 0.003 mg/kg body weight per day. The only source for the chemical is freshwater fish, where it occurs at an average level of 0.2 ppm. What is the maximum average daily consumption of such fish that would keep exposure level below the ADI or RfD for the compound? PLEASE NOTE: This is the second time that this question has been posted as the first response received was not correct. When the first response was entered online, the computer offered the following hint: Assume safety factor of 100, 60 kg person. I tried t... click for more

For a solution having 0.0009 equivalents/liter total alkalinity...percentage contribution to alkalinity from CO32...

Please only respond if you are 100% sure as this question has already been posted once. 12) (contributions from HCO3-, CO32, and OH-) at [H+] = 4.69E-11, what is the percentage contribution to alkalinity from CO32? PLEASE NOTE: This is the second time that this question has been posted as the first response received was not correct. When the first response was entered online, the computer offered the following hint: Calculate the bicarbonate concentration and the contribution of the bicarbonate to the total alkalinity. The response is NOT: 1.04 x 10 -5 % nor is it 76.3 %