(PLEASE HELP) A 300 ml water sample was taken from a stream in Mexico City and analyzed for dissolved oxygen. Using the Winkler method, 58.88 ml of 2.42 x 10^-3 M sodium thiosulfate titrant was required. Calculate the dissolved oxygen in the water and express this as mg/L.

Which solution is an example of a nonelectrolyte? a. iodine in hexane b. sodium nitrate in waterc. acetic acid in waterd. hydrogen chloride in water

Aroom with dimensions 7.00m×8.00m×2.50m is to be filled with pure oxygen at 22.0∘c and 1.00 atm. the molar mass of oxygen is 32.0 g/mol. how many moles noxygen of oxygen are required to fill the room? what is the mass moxygen of this oxygen?

Answer asap need by wednesday morning explain how a buffer works, using an ethanoic acid/sodium ethanoate system including how the system resists changes in ph upon addition of a small amount of base and upon addition of a small amount of acid respectively. include the following calculations in your i. calculate the ph of a solution made by mixing 25cm3 0.1m ch3cooh and 40cm3 0.1m ch3coo-na+. [ka = 1.74 x 10-5 m] ii. calculate the ph following the addition of a 10cm3 portion of 0.08 m naoh to 500cm3 of this buffer solution. iii. calculate the ph following the addition of a 10cm3 portion of 0.08 m hcl to 200cm3 of the original buffer solution.