Give one example of chemical reaction each
1•evolution of gas
2•change in colour
3•formation of a precipitate
4•change in temp
5•change in state
Answers
1. Zn+ H2SO2----> ZnSO4+ H2 (evolution of hydrogen gas)
2. Pb(NO3)2+ 2KI-----> PbI2+ 2KNO3 (colorless to yellow)
3. BaCl2 +Na2SO4-----> BaSO4 +2NaCl (BaSO4 is a precipitate)
4. Zn+ H2SO4------> ZnSO4+ H2 (Heat is evolved)
5. When wax is burned in the form of wax candle then Water and carbon dioxide are formed. Wax is a solid water is a liquid whereas carbon dioxide gas.
Answer:
1. Change in colour :
The reaction between lead nitrate solution and poassium iodide solution.
Chemical equation as follow :
Pb ( NO₃ )₂ + 2 KI ⇒ PbI₂ + 2 KNO₃
In above reaction colour change from colourless to yellow.
2. Change in temperature :
The reaction between dil. sulphuric acid on zinc.
Chemically :
Zn + H₂SO₄ ⇒ ZnSO₄ + H₂
Heat evolved in the above reaction.
3. Formation of precipitation :
The reaction between barium chloride on sodium sulphate.
Chemically :
BaCl₂ + Na₂SO₄ ⇒ BaSO₄ + 2 NaCl
In the above reaction white ppt. of BaSO₄ will form.