Question

Nitrate salts (NO3), when heated, can produce nitrites (NO2) plus oxygen (O2). A sample of potassium nitrate is heated, and the 02 gas produced is collected in a 700 mL flask. The pressure of the gas in the flask is 2.7 atm, and the temperature is recorded to be 329 K. The value of R= 0.0821 atm L/(mol K) How many moles of O2 gas were produced? moles After a few hours, the 700 mL flask cools to a temperature of 293K. What is the new pressure due to the O2 gas?

Answer 1

Answer: a) 0.070 moles of oxygen were produced.

b) New pressure due to the oxygen gas is 2.4 atm

Step-by-step explanation:

According to ideal gas equation:

`PV=nRT`

P = pressure of gas = 2.7 atm

V = Volume of gas = 700 ml = 0.7 L

n = number of moles = ?

R = gas constant =
`0.0821Latm/Kmol`

T =temperature = 329 K

`n=(PV)/(RT)`

`n=(2.7atm* 0.7L)/(0.0821 L atm/K mol* 329K)=0.070moles`

Thus 0.070 moles of oxygen were produced.

When the 700 mL flask cools to a temperature of 293K.

`PV=nRT`

`P=(nRT)/(V)`

`P=(0.070* 0.0821* 293)/(0.7)`

`P=2.4atm`

The new pressure due to the oxygen gas is 2.4 atm