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Question
Explain by writing a word equation.
Hard water gets softened on mixing with a solution of washing soda.
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Solution
To soften the hard water, a solution of washing soda is added to it. This results in a chemical reaction to form a precipitate of insoluble carbonate salts of calcium and magnesium. As the dissolved salts of calcium and magnesium go out in the form of a precipitate of the carbonate salts, the water is softened. The following equation can be written for this chemical change.
Word equation:
Calcium chloride + Sodium carbonate `→` Calcium carbonate + Sodium chloride
Chemical equation (unbalanced):
CaCl2 + Na2CO3 → CaCO3 + NaCl
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How do the following help in bringing about a chemical change?
heat.
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Reduction is a chemical reaction in which there is
- removal of hydrogen
- removal of oxygen
- addition of oxygen
- none of these
Complete the statement by filling the gap using an appropriate term from the terms given in the bracket.
(slow, coloured, arrow, fast, smell, milky, physical, product, chemical, reactant, covalent, ionic, octet, duplet, exchange, sharing, equality sign)
An ______ is drawn in between the reactants and products while writing the equation for a chemical reaction.
Explain by writing a word equation.
Limestone powder disappears on adding to dilute hydrochloric acids.
Write the chemical reaction where the following changes are observed.
Precipitate is formed
Multiple choice:
Which of the following is not a characteristic of a chemical change?
Give two examples where a chemical reaction is accompanied by a change in colour of the reactants and products on completion of the reaction.
Give a balanced equation for the conversion of an ammonium salt to a basic gas.
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Do you think formation of rust from iron is a chemical change?
Write a note on the following:
Fermentation
