Work this out like this Chroium you are told is oxidation state +3. Selenium is in group 16 along with oxygen and sulfur so it will have a preferred oxidation state of -2. Then balance it, oxidation staes can be treated like ionic charges:-
Cr2Se3
Formula: Cr2Se3
Chromium(III) nitrate is Cr(NO3)3
That would be chromium(II) sulfate, but really, chromium mostly exists as Cr(III) or Cr(VI), which would change the formula.
There would be no reaction because tin will not replace the chromium in the chromium (III) acetate. Refer to the related link for an activity series for metals.
The formula is CrN. It is called Chromium nitride and Chromium(III) nitride. Chromium also forms second interstitial nitride, dichromium nitride - Cr2N
Chromium (II) chloride = CrCl2Chromium (III) chloride = CrCl3 Chromium (IV) chloride = CrCl4
The chemical formula of iron(III) and selenium is Fe2Se3 - iron(III) selenide.
The chemical formula of chromium(III) arsenate is CrAsO4.
Chromium(III) phosphide has the formula CrP.
the chemical formula for chromim(II) fluoride is CrF2
The chemical formula for chromium (III) sulfate is Cr2(SO4)3.
CrI3
Chromium(III) nitrate is Cr(NO3)3
Chromium(III) borate has the chemical formula CrBO3.
Cr2(CO3)3 = 3 CO2 + Cr2O3
Cr2O3 is the chemical formula for chromium (III) oxide
That would be chromium(II) sulfate, but really, chromium mostly exists as Cr(III) or Cr(VI), which would change the formula.
Cr(SCN)3 is the chemical formula for the Chromium (III) Thiocyanate. This is because Chromium (III) has a charge of +3 while Thiocyanate has a charge of -1. To balance the charges, we switch the 2 charges. So we have 1 ion of chromium (III) with 3 ions of thiocyanate.