JEE Advanced 2020 · Paper 2 · Chemistry Q4

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ChemistryInteger+3 / -1Question 22 of 54

An acidified solution of potassium chromate was layered with an equal volume of amyl alcohol. When it was shaken after the addition of 1 mL of 3% $\ce{H2O2}$ , a blue alcohol layer was obtained. The blue color is due to the formation of a chromium (VI) compound 'X'. What is the number of oxygen atoms bonded to chromium through only single bonds in a molecule of X?

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Answer and worked solution

Official answer: 4

Acidified chromate with $\ce{H2O2}$ gives chromium peroxide, $\ce{CrO5}$ ( $\ce{CrO(O2)2}$ ), which dissolves in amyl alcohol with a blue colour. Chromium is +6.

Structure. One oxygen is double-bonded to Cr. The other four belong to two peroxo ( $\ce{O-O}$ ) groups, each bonded to Cr by single bonds.

Answer: 4

Topics:Important compounds (KMnO4, K2Cr2O7)Covalent bonding and Lewis structures

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JEE Advanced 2020 · Paper 2, Chemistry question 4