Lab retreat scientific quiz

How many molecules of H₂O typically surrounds an Fe²⁺ ion in aqueous solution?

• 2

• 4

• 6

• 8

Answer explanation

What is the typical concentration of Fe²⁺ in circumneutral anoxic environments in nature?

• <1 uM

• 1-1,000 uM

• 1-10 mM

• 10-100 mM

Answer explanation

Which of these is not a stable isotope of Fe?

• ⁵⁴Fe

• ⁵⁵Fe

• ⁵⁶Fe

• ⁵⁸Fe

Answer explanation

What is the typical pH of seawater?

• 5-6

• 6-7

• 7-8

• 8-9

What is the typical size of a ferrihydrite crystallite?

• 2-5 nm

• 5-100 nm

• 100-1,000 nm

• > 1 um (visible by eye)

Answer explanation

Weatherill et al. (2016)

Which of these is not a mixed-valent Fe mineral?

• 
• 
• 
• 

Answer explanation

Strengite is an Fe(III) phosphate mineral.

Which of these processes does NOT lead to an increase in Fe mineral crystallinity?

• Al-catalyzed recrystallization

• Fe(II)-catalyzed recrystallization

• Heating in the autoclave

• Aging via time

Answer explanation

Caraballo et al. (2022)

The energy available from microbial Fe(III) reduction _______ with increasing pH.

Hint: write down the balanced equation of Fe(OH)₃ being reduced by CH₂O

• Increases

• Decreases

• Stays constant

Answer explanation

4 Fe(OH)_³ + CH₂O + 8 H⁺ --> 4 Fe²⁺ + CO₂ + 11 H₂O2

Jin & Kirk (2018) "pH as a Primary Control in Environmental Microbiology:

1. Thermodynamic Perspective"

How many species of Geobacter have been isolated into pure cultures?

• 5-10

• 10-15

• 15-20

• >20

Answer explanation

Over 20. I went through the list from DSMZ, ATCC and other culture collections

What is the typical pH of rainwater?

• 4-5

• 5-6

• 6-7

• 7-8