change in colour, evolution of gas, change in temperature examples two of each
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10th
Chemistry
Chemical Reactions and Equations
Chemical equation
Give one example each of a ...
CHEMISTRY
Give one example each of a chemical reaction characterised by
1.Evolution of a gas.
2.Change in colour.
3.Formation of a precipitate.
4.Change in temperature.
5.Change in state.
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ANSWER
1.Evolution of gas:
The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen gas.
Zn(s)+H
2
SO4(aq)→ZnSO
4
(aq)+H
2
(g)
2.Change in colour:
The reaction between the lead nitrate solution and potassium iodide solution.
Pb(NO
3
)
2
(aq)+2KI→PbI
2
(s)+2KNO
3
(aq)
In this reaction colour changes from colourless to yellow.
3.Formation of precipitate:
The action of Barium Chloride on sodium sulphate.
BaCl
2
(aq)+Na
2
SO
4
(aq)→BaSO
4
(s)+2KNaCl(aq)
4.Change in temperature change in temperature:
The action of dilute sulphuric acid on zinc:
Zn(s)+H 2 SO 4 (aq)→ZnSO 4 (s)+H 2(g)
In this reaction, heat is evolved.
5.Change in the state:
When the wax is burnt in the form of the wax candle then Water and carbon dioxide are formed. Wax is solid water is a liquid whereas carbon dioxide gas.
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Answer:
change in colour Example = Copper reacts with oxygen, H2O and CO2 to give copper carbonate, which changes color from brown to blue or blue green, evolution of gas = example, carbonic acid breaks down to water and carbon dioxide, sulfurous acid breaks down to water and sulfur dioxide, and ammonium hydroxide breaks down to water and ammonia gas.,CHANGE in temperature examples When quicklime reacts with water, slaked lime is formed with a release of large amount of heat, causing change in temperature in the reaction mixture