Question

2) Bacterial digestion is an economical method of sewage treatment. The reaction 5CO21l@)+55NH(aq)+76021)CsH20N) + 54NO2 (aq)+52H2O()+ 109H (aq) Bacterial tissue is an intermediate step in the conversion of the nitrogen in organic compounds into nitrate ions. What mass of bacterial tissue is produced in a treatment plant for every 1.0x10 kg of wastewater containing 3.0% NHa ions by mass? Assume that 95% of the ammonium ions are consumed by the bacteria. (Bacterial tissue is CsH,O2Ns) (10)

Answer 1

Mass of waste water

1.0 x 104 kg x 1000 g/kg = 1.0 x 10 g

Mass percent of ammonium ions is 3.0 %.

Mass of ammonium ions present in waste water

3.0 = 1.0 x 10 g x = 3.0 x 105 100

95% of ammonium ions are consumed by the bacteria.

Mass of ammonium ions consumed by bacteria

95 3.0 x 10 g x -2.85 x 105 100

Molar mass of ammonium ions

NH14 4(1) 18 g/mol

Number of moles of ammonium ions consumed by bacteria

2.85 x 10 g 1.58 x 104 mol 18 g/mol

Number of moles of bacterial tissue produced

1 mol bacterial tissue 1.58x 104 mol NH ionsx 287.9 mol bacterial tissue 55 mol NHt ions

Molar mass of bacterial tissue

C5H7O2N = 5(12)7(1)2(16) 14 607+32+14= 113 g/mol

Mass of bacterial tissue produced

287.9 mol bacterial tissue x 113 g/mol 3.3 x 104 g bacterial tissue