Washing Soda
Washing soda is sodium carbonate decahydrate, a basic salt used for cleaning and softening hard water.
Practice This ConceptMain explanation
Teacher explanation
Washing soda is an important salt in this chapter because it has practical uses in cleaning and in removing hardness from water. It helps because it reacts with calcium and magnesium ions, so soap can work better in hard water. It is different from baking soda and should not be confused with it. The hydrated form is commonly written as Na2CO3·10H2O.
Example
A laundry shop may add washing soda to hard water so that soap lathers properly.
Simple analogy
Washing soda washes better in hard water.
Common confusion
Students often confuse washing soda with baking soda because both are white powders used in homes. Their formulas and uses are different.
Exam tip
For exam questions, remember that washing soda softens hard water and its formula includes water of crystallisation.
Answer writing and exam use
1-mark use
Write the exact meaning of washing soda in one clean line.
2-mark use
Define washing soda and add one example or condition.
3-mark use
Explain washing soda, show the method or example, and mention the common mistake.
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