Question

A 3.31 g sample of lead nitrate, Pb(NO 3 ) 2 , molar mass = 331 g/mol, is heated in an evacuated cylinder with a volume of 1.62 L. The salt decomposes when heated according to the equation: . Assuming complete decomposition, what is the pressure in the cylinder after decomposition and cooling to a temperature of 300 K? Assume the PbO takes up negligible volume.

Answer 1

`P=0.152\ atm`

Step-by-step explanation:

Given:

• The volume of the cylinder,
  `V=1.62\ L`

• The mass of the sample,
  `m=3.31\ g`

• The temperature,
  `T=300\ K`

• The molar mass of lead nitrate is
  `M=331\ g/mol`

Now, no. of moles:

`n=(m)/(M)`

where:

m = mass in gram

M = molecular mass

`n=(3.31)/(331)`

`n=0.01\ mol`

From the ideal gas law:

`P.V=n.R.T`

`P* 1.62=0.01* 0.08206*300`

`P=0.152\ atm`