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Acids, Bases and Salts — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceAcids, Bases and Salts5 Marks
Question
How would you distinguish between baking powder and washing soda by heating?
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Answer

Baking soda is sodium hydrogen carbonate (NaHCO3) which forms sodium carbonate (Na2CO3), water and carbon dioxide gas while heating.

$2\text{NaHCO}_3\rightarrow\text{Na}_2\text{CO}_3+\text{H}_2\text{O + CO}_2\uparrow$

Presence of CO2 can be detected with the help of lime water which turns milky after reacting with carbon dioxide gas

Washing soda is sodium carbonate deca-hydrate (Na2CO3.10H2O) which means there are 10 water molecules present with crystal hence named as water of crystallization

On heating washing soda, it becomes anhydrous and presence of water of crystallization can be detected with the help of anhydrous CuSO4 which shows colour change from white to blue with moisture.

Na2CO3.10H2O → Na2CO3 + 10H2O

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