Answer:
You can divide the mass by the volume to calculate the density of the metal
Explanation:
 
        
             
        
        
        
Reaction for precipitation is
Pb(NO3)2(aq) + 2Nacl(aq)→PbCL2(s)+2NaNO3(aq)
The given reaction is 
The mol of Nacl required is =2×mol of Pb(NO3)2 which is present.
∴M(Nacl)×V(Nacl) =2×M(Pb(NO3)2 ×V(Pb(NO3)2
o.100M×V(Nacl)=2×0.200 MX75.0ML
V(Nacl = 300mL.
        
             
        
        
        
  The volume that  will  be occupied at 735  torr and 57 c  is  23.12 L
  <u><em>calculation</em></u>
- <u><em> </em></u> At STP   temperature=273 k  and  pressure=760 torr
- <u><em> </em></u>by use of combined  gas formula 
that is P1V1/T1= P2V2/T2
where; P1 =760 torr
            T1= 273  K
            V1= 18.5 L
           P2= 735 torr
          T2=  57+273= 330 K
           V2=?
- by making   V2 the formula of subject
      V2= T2P1V1/P2T1
        V2=  [(18.5L  x 330 k  x 760 torr)/(735 torr x 273 k)]= 23.12  L