Nitrate salts (NO3-), when heated, can produce nitrites (NO2-) plus oxygen (O2). A sample of potassium nitrate is heated, and the O2 gas produced is collected in a 720 mL flask. The pressure of the gas in the flask is 2.9 atm, and the temperature is recorded to be 319 K. The value of R= 0.0821 atm L/(mol K)

How many moles of O2 gas were produced?

After a few hours, the 720 mL flask cools to a temperature of 293K.

Pnew = atm

What is the new pressure due to the O2 gas?