JEE Main 2023 · 15 April · morning · Numerical answer · +4 / −0

In Chromyl chloride, the oxidation state of chromium is (+) _______________.

Answer and solution

Answer 6

Solution

Chemistry ma’am · 3 steps

Write the formula first: chromyl chloride is CrO₂Cl₂, then let the charges balance to zero.

  1. Get the formula. Chromyl chloride is CrO₂Cl₂: one chromium, two oxygens and two chlorines. It is a neutral molecule, so all the oxidation states add up to zero.
  2. Known values. Oxygen is -2 here, since this is not a peroxide. Chlorine is -1, because it is bonded to chromium, a less electronegative atom.

    x + 2(-2) + 2(-1) = 0 ⇒ x = +6

  3. So. Chromium is in the +6 state in CrO₂Cl₂, the same as in dichromate. The answer is 6.

The common slip: 4. Writing chromyl chloride as CrOCl₂ with only one oxygen gives x - 2 - 2 = 0, which is 4, not 6.

The idea to keep. For a named compound, write the correct formula before anything else. Then fix the atoms you know (O as -2, halogen as -1) and let the sum to zero give you the metal.

Answer from the NTA final answer key. Solution by PrepWiser.

Study Redox Reactions

Asked about 90 times in JEE Main since 2020. This question is from 2023.