Question

1) when kl-solution is added to a solution of lead (ll)- nitrate (pb(No3)2) in a test tube , a precipitate is formed

a- what is the colour of this precipitate ?
b- name the compound precipiitate
c- write the balance chemical equation for this reaction
d- what type of reaction is this ?

2)balance the following chemical equation ;
HNO3 + Ca(OH)2 ------> Ca(NO3)2 + H2O


3)why does the colour of copper sulphate solution change when an iron nail is dipped in it ?

4) when zinc granules are added to dil.sulphuric acid, a gas is evolved . write the name of the gas and reaction taking place .

Answer 1

1. a. Yellow Colour precipitate of Lead Iodide is formed
    b. It is nothing but Lead Iodide
    c. 2KI (aq) + Pb(NO3)2 (aq) ---------> PbI2 (gas) + 2KNO3 (aq)
    d. It is Chemical double Displacement Reaction.

2. Ca(OH)2 + HNO3 --> Ca(NO3)2 + H2O 
   OH2 on left and 1 on right side - put a 2 in front of H2O 
   Then the reaction will be,
   Ca(OH)2 + HNO3 --> Ca(NO3)2 + 2H2O 
   Ca is balanced on both sides.
   H is not balanced on both sides 
   So, keep 2 in front of HNO3 
   Then the reaction will be
   Ca(OH)2 + 2HNO3 --> Ca(NO3)2 + 2H2O 
   2 NO3 is balanced on both sides
   Hence the equation is balanced
   therefore the balanced equation is:
   Ca(OH)2 + 2 HNO3 -->  Ca(NO3)2 + 2 H2O

3. The colour of copper sulphate solution change when an iron nail is dipped in it. Because Iron is more reactive than copper. We know that the more reactive elements are displaced to the position of less reactive ones. So due to the reaction that takes place here, the Iron nail turned into brownish colour and the copper sulphate colour gets fades.

4.  when zinc granules are added to dil.sulphuric acid, a gas is evolved. It is nothing but Hydrogen.
 the reaction occured here is shown in the form of equation.
 Zn + H2SO4 -------------> ZnSO4 + H2 (gas)
hence, the gas evolved here is Hydrogen.