A compound ‘X’ is bitter to taste. It is compound of washing powder and reacts with dilute HCl to produce brisk effervescence due to a colourless and odourless gas ‘Y’ which turns lime water milky due to the formation of ‘Z’ when an excess of CO2 is passed, milkiness disappears due to the formation of ‘P’. Identify ‘X’. ‘Y’, ‘Z’ and ‘P’. Write the equations involved in the formation of Y, Z, and P.

Since the compound X is a washing powder then it has to be sodium carbonate whose common name is washing powder. When sodium carbonate reacts with dilute HCl, carbon dioxide gas is liberated.

This gas reacts with lime water to form calcium carbonate which gives the temporary milky appearance.


On further passing the gas, the calcium carbonate reacts to calcium bicarbonate and the milky appearance disappears.


X is Sodium Carbonate [Na2CO3]


Y is Carbon Dioxide [CO2]


Z is Calcium Carbonate [CaCO3]


P is Calcium Bicarbonate [Ca (HCO3)2]


The reactions is as follows:


Na2CO3 + 2HCl 2NaCl + H2O + CO2


Ca (OH) 2 + CO2 CaCO3 + H2O


CaCO3 + CO2 + H2O Ca (HCO3)2


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