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COMEDK2024Chemistryd and f Block Elements

Which of the following compounds on reaction with NaOH and Na ₂ O ₂ gives yellow colour?

Options

  1. AZn ( OH )₂
  2. BAl ( OH )₃
  3. CCr ( OH )₃
  4. DCaCO ₃

Correct answer

C. Cr ( OH )₃

Step-by-step solution

Yellow colour is obtained due to the formation of CrO ₄²⁻ (chromate) ion when Cr ( OH )₃ is oxidised by Na ₂ O ₂ in basic medium. The complete reaction is as follows, Cr ( OH )₃+ NaOH + Na ₂ O ₂ Na ₂ CrO ₄+2 H ₂ O

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