Question

Farmers use ammonium sulfate as a fertilizer. In the soil, nitrifying bacteria oxidize NH4+ to NO3−, a groundwater contaminant that causes methemoglobinemia ("blue baby syndrome"). The World Health Organization standard for maximum [NO3−] in groundwater is 45 mg/L. A farmer adds 197 kg of (NH4)2SO4 to a field, and 37.0% is oxidized to NO3−.

What is the groundwater [NO3−] (in mg/L) if 1,000. m3 of the water is contaminated?

Answer 1

Each molecule will produce two ions.

Amount of added = 197 kg = 197000 gm.

Molar mass of = 132 gm/mol.

Hence, number of moles of in the fertilizer is

Each mole of dissociates into two moles of .

Hence, the number of moles of available to the nitrifying bacteria to oxidise is

It is given that only 37% of the is oxidized.

hence, the number of moles of that has been oxidized is

Hence, the number of moles of produced is 1104.4 mol.

Molar mass of = 62 gm/mol.

Hence, amount of that has been produced by the bacteria is

Totat volume of the groundwater that is contaminated = .

Hence, the groundwater can be written as

The concentration of 68.5 mg/L is more than the maximum set by WHO.