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Which of the following species gives colourless and odourless gas on thermal decomposition :

(NH4)2Cr2O7

Pb(NO3)2

ZnSO4.7H2O

(NH4)2SO4

User Reignbeaux
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Answer:

(NH4)2SO4 gives colourless and odourless gas, which is ammonia (NH3), on thermal decomposition. This is because ammonium sulfate decomposes upon heating to produce ammonia gas and water:

(NH4)2SO4 → 2NH3 + H2O + SO2

The other compounds listed in the question do not produce colourless and odourless gases on thermal decomposition.

- Pb(NO3)2 decomposes to form nitrogen dioxide gas, which has a reddish-brown color and a pungent odor.

- ZnSO4.7H2O decomposes to form water vapor and sulfur dioxide gas, which has a pungent odor and a choking sensation.

- (NH4)2Cr2O7 decomposes explosively to form nitrogen gas, water vapor and chromium oxide, which has a green color.

Therefore, the correct answer to the question is (NH4)2SO4.

User Dave Challis
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