A hydrated solid X on heating initially gives a monohydrated compound Y. Y upon heating above 373 K leads to an anhydrous white powder Z. X and Z, respectively, are:

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JEE Mains Previous Paper 1 (Held On: 10 Apr 2019 Shift 2)
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  1. Washing soda and soda ash.
  2. Baking soda and dead burnt plaster.
  3. Washing soda and dead burnt plaster.
  4. Baking soda and soda ash.

Answer (Detailed Solution Below)

Option 1 : Washing soda and soda ash.
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JEE Main 04 April 2024 Shift 1
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Detailed Solution

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Concept:

The reaction is given below:

Na2 CO3.10H2O ⟶ Na2 CO3.H2O + 9H2O

            (X)                    (Y)

Na2 CO3.H2O ⟶ Na2 CO3 + H2O

 (Y)                   (Z)

Here, X represents Washing soda

Y represents Washing soda (monohydrated)

and Z represents Soda ash

When washing soda is heated which undergoes dehydrogenation to form washing soda. Then again heated above 373 K to form sodium carbonate powder with very less water content that is soda ash.

Thus, the required X and Z are Washing soda and soda ash respectively.
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