Question

reactions characterised b

y evolution of gas and formation of precipitate and change in color and change in temperature and change in state

Answer 1

Evolution of gas➡CuO+H2O=Cu(OH)2
Precipitate➡Pb(NO3)+KI=PbI+K(NO3)
Change in color➡Mg+O2=MgO
Change in state➡Candle burn in air to get H2O(Liquid) & CO2.

Answer 2

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.