Question

write four characteristics of chemical equation​

Answer 1

Answer:

change in colour and temperature

Explanation:

evolution of gas

Answer 2

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Evolution of a Gas:

• Some chemical reactions are characterized by the evolution of a gas.
• The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen gas.
• Take some zinc granules in a conical flask.
• Add dilute sulphuric acid over zinc granules.
• We will see the bubbles of hydrogen gas being formed around zinc granules.
• If we touch the conical flask with our hand, we will find that it is somewhat hot. So, a change in temperature also occurs in this chemical reaction.

Formation of a precipitate:

• Some chemical reactions are characterized by the formation of precipitate. A precipitate is a ‘solid product’ which separates out from the solution during a chemical reaction.
• The chemical between potassium iodide and lead nitrate is characterized by the formation of a yellow precipitate of lead iodide.
• Take some lead nitrate solution in test tube.
• Add potassium iodide solution to it.
• A yellow precipitate of lead iodide is formed at once.
• A change in colour also takes place in this chemical reaction.

Change in colour:

• Some chemical reactions are characterized by a change in color.
• The chemical reaction between citric acid and purple colored potassium permanganate solution is characterized by a change in color from purple to colorless.
• Take some dilute potassium permanganate solution in a test tube. It has purple colour.
• Add some lemon juice (it contains citric acid) to it with the help of a dropper and shake the test tube.
• The purple color of potassium permanganate solution goes on fading and ultimately it becomes colorless.  

Change in temperature:

• Some chemical reactions are characterized by a change in temperature.
• The chemical reaction between quicklime and water to form slaked lime is characterized by a change in temperature.
• Take a little of quicklime in a hard-glass beaker.
• Add water to it slowly.
• Touch the beaker.
• The beaker feels to be quite hot.

Change in state:

• Some chemical reactions are characterized by a change in state.
• When wax is burned (in the form of wax candle), then water and carbon dioxide are formed.
• Now, wax is a liquid whereas carbon dioxide is a gas. This means that during the combustion reaction of wax, the physical state changes from solid to liquid and gas.

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