Hey there!:
Given the mass of PbCl(OH) :
0.135 Kg = 0.135 Kg*(1000g / 1Kg) = 135 g
Molecular mass of PbCl(OH) = 207+35.5+16+1 = 259.5 g / mol
Atomic mass of Pb = 207 g/mol
Hence mass of Pb in 135 g PbCl(OH) :
(207 g Pb / 259.5 g PbClOH) * 135g PbClOH =
0.79768 * 135 => 107.68 g of Pb
For Pb2Cl2CO3 :
Given the mass of Pb2Cl2CO3 :
0.135 Kg = 0.135 Kgx(1000g / 1Kg) = 135 g
Molecular mass of Pb2Cl2CO3 = 2*207+2*35.5+12+3*16 = 545 g / mol
Mass of Pb present in 1 mol (=545 g / mol) of Pb2Cl2CO3 = 2*207 = 414 g
Hence mass of Pb in 135 g Pb2Cl2CO3:
(414 g Pb / 545 g PbClOH) * 135g PbClOH =
0.75963 * 135 => 102.55 g of Pb2Cl2CO3
Hope that helps!
Answer: -
12.41 g
Explanation: -
Mass of CO₂ = 42 g
Molar mass of CO₂ = 12 x 1 + 16 x 2 = 44 g / mol
Number of moles of CO₂ = 
= 0.9545 mol
The balanced chemical equation for this process is
2C₆H₆ + 15O₂ → 12CO₂ + 6H₂O
From the balanced chemical equation we see
12 mol of CO₂ is produced from 2 mol of C₆H₆
0.9545 mol of CO₂ is produced from 
= 0.159 mol of C₆H₆
Molar mass of C₆H₆ = 12 x 6 + 1 x 6 =78 g /mol
Mass of C₆H₆ =Molar mass x Number of moles
= 78 g / mol x 0.159 mol
= 12.41 g