Chemistry
posted by mary .
a 2.16g sample of Pb(NO3)2 is heated in an evacuated cylinder with a volume of 1.18L. the salt decomposes when heated: 2Pb(NO3)2 (s)_> 2PbO (s) +4NO2 (g) +O2 (g) Assuming complete decomposition, what is the pressure in the cylinder after decomposition and cooling to a final temperature of 303K?

Convert 2.16 g Pb(NO3)2 to moles. moles = grams/molar mass.
Using the coefficients in the balanced equation, convert moles Pb(NO3)2 to
a. moles NO2, and
b. moles O2.
Add moles gases, substitute into PV = nRT at the conditions listed and solve for P.