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प्रश्न
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Thermal decomposition of mercury [II] oxide.
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उत्तर
Thermal decomposition of mercury [II] oxides: Red colour of Hg[II]0 changes to silvery (Hg metal).
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Iron pipes coated with zinc do not get rusted easily.
Complete and balance the following chemical equations:
N2 + O2 →
Complete and balance the following chemical equations:
`"H"_2"S"` + `"CI"_2` `→`
Complete and balance the following chemical equations:
Zn + `"H"_2"SO"_4` `→`
(dil)
FILL IN THE BLANK
In a double decomposition precipitation reaction both the reactants must be ............ soluble.
Fill in the blank:
In some chemical reactions an insoluble ________ is formed when two solutions are mixed.
Write true or false :
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State what you would observe when the following substance is heated in a glass test tube red lead.
Write your observation and a balanced equation in the case of the following substances being heated.
Ammonium dichromate.
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A coloured substance which leaves on strong heating a black residue and evolves two colourless gases one of which is acidic and the other neutral.
Give a balanced equation for a reaction involving the evolution of gas on the addition of dilute acid to calcium carbonate.
Higher order Thinking question
A very hot glass on putting in cold water cracks. What does this change indicate?
A reaction between an acid and a base is called ______.
Give an example of a chemical reaction for the following situation:
A change in colour is observed
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Can you change rust back into iron by some simple method?
Vanaspati is obtained from vegetable oils by the addition of ______ to the oils.
Galvanization is a process in which ______ is coated as a layer of iron.
How would you show that the settling of curd is a chemical change?
Explain how the painting of an iron gate prevents it from rusting.
______ is a chemical substance is used in whitewashing.
