Which chemical compound is commonly known as 'Washing Soda' and used in domestic and indus… — State PSC Exam

Which chemical compound is commonly known as 'Washing Soda' and used in domestic and industrial applications for softening hard water?

Sodium carbonate decahydrate ( $Na_2CO_3 \cdot 10H_2O$ )Answer
B
Sodium hydrogen carbonate ( $NaHCO_3$ )
C
Calcium sulphate hemihydrate ( $CaSO_4 \cdot \frac{1}{2}H_2O$ )
D
Calcium hydroxide ( $Ca(OH)_2$ )

Answer

Sodium carbonate decahydrate (

Na_2CO_3 \cdot 10H_2O

)

The compound sodium carbonate decahydrate (

Na_2CO_3 \cdot 10H_2O

) is commonly referred to as Washing Soda. It is extensively used in laundry cleaning and industrial processes to remove permanent hardness from water by precipitating calcium and magnesium ions.

Step-by-Step Solution

Identify the common chemical name 'Washing Soda'

Washing soda corresponds to hydrated sodium carbonate.

Chemical nomenclature assigns specific common names to hydrated salts used in daily life.

Determine the exact chemical formula

Na_2CO_3 \cdot 10H_2O

containing ten water molecules of crystallization.

Anhydrous sodium carbonate (

Na_2CO_3

) is known as soda ash; recrystallization from water gives washing soda.

Verify industrial application

It reacts with soluble

Ca^{2+}

and

Mg^{2+}

ions to form insoluble carbonates (

CaCO_3

and

MgCO_3

), thereby removing permanent hardness.

Precipitating metal ions reduces soap consumption and prevents scum formation.

Key Concept

Chemical nomenclature and applications of sodium compounds in daily life

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