Question

give one example each of a chemical reaction characterised by: (i) evolution of a gas (ii)change in color (iii)formation of a precipitate (iv)change in temperature (v)change in state

Answer 1

i) Evolution of gas--- Reaction between zinc and dilute sulphuric acid
ii) Change in color--- Reaction between citric acid and purple colored potassium permanganate solution gives colourless solution.
iii) Formation of precipitate--- Reaction between potassium iodide and lead nitrate forms a yellow precipitate of lead iodide.
iv) Change in temperature: Reaction between zinc granules and dliute hydrochloric acid.
v) Change in state: Combustion of candle wax is characterized by a change in state from solid to liquid and gas.
 

Answer 2

i) zn+h2so4=znso4 +h2

ii) agcl=ag+cl2

iii)bacl2+na2 so4 =baso4 +2nacl

iv) cao+h2o=caoh2 +heat