Answer:
When the metal of the ionic compound has multiple oxidation states.
Explanation:
Nickel (Ni - At No 28) has multiple oxidation states* => −2, −1, 0, +1,[2] +2, +3, +4[3] (a mildly basic oxide)*. When naming compound of nickel on needs to include a roman numeral in parenthesis after the symbol of the element in order to identify which oxidation state is relevant.
examples
Nickel Halide derivatives include
NiCl => nickel(I) chloride
NiCl₂ => nickel(II) chloride
NiCl₃ => nickel (III) chloride
Such is important in that each of the compounds have different physical and chemical properties due to variations in oxidation states of nickel.
https://en.wikipedia.org/wiki/Nickel
B. Increases because the more liquid there,the more time is needed to boil it
B ase from the reaction <span>cacn2 3 h2o → caco3 2 nh3, for every 1 mole of caco3 produced there 2 moles of nh3 being produced. to solved this, we must first convert the caco3 to moles.
mass nh3 = 187 g caco3 (1 mol caco3 / 100 g caco3 ) ( 2 mol nh3 / 1 mol caco3) ( 17 g nh3 / 1 mol nh3)
mass nh3 = 63.58 g nh3 is produced</span>
