What does the name iron(ii) in a compound indicate about the cation?

2+ charge           is the answer

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Explanations:- Transition elements shows variable oxidation states. So, while naming these compounds we use the roman numerals to tell their oxidation states.

For example, if someone writes just Iron oxide then it would not be correct since Iron could be in +2 or +3 states. So, it might be or . So, the right was is to mention the oxidation state of the transition metal.

If the name is written as Iron(II) in a compound then it means there is +2 charge on iron and it is .

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.