Pb(OH)2 + 2 HCl = 2 H2O + PbCl2
If it is heated while it is being compressed or held inside a container as such, the pressure build up while in the container and the pressure can become so much that the container will burst.
Using ideal gas equation,
P\times V=n\times R\times T
Here,
P denotes pressure
V denotes volume
n denotes number of moles of gas
R denotes gas constant
T denotes temperature
The values at STP will be:
P=100 kPa
T=293 K
R=8.314472 L kPa K⁻¹ mol⁻¹
Number of moles of gas=3.43 mole
Putting all the values in the above equation,

V=83.55 L
So the volume will be 83.55 L.
83.55 L of radon gas would be in 3.43 moles at room temperature and pressure (293 K and 100 kPa).

given E = 9.4145E-25
h = 6.626E-34
c = 2.998E8
sub values into the equation above, and solve for wavelength.
You will get 0.211m