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?

0.07973 moles of O2 gas were produced

2.66 atm

Explanation:

Using the ideal gas equation

PV =nRT

P =pressure = 2.9 atm

V= volume = 720 mL =  720mL/1000= 0.72 L

n = number of moles = ?

R = the gas constant = 0.0821 atm L/(mol K)

T = temperature in Kelvin = 319 K

make n subject of the formula

n =PV/RT

n = 2.9 atm x 0.72 L / 0.0821 atm L/(mol K) x 319K = 0.07973 moles of O2 gas were produced

Pnew = atm?

P = nRT/V

 = 0.07973 x 0.0821 atm L/(mol K) x 293K/0.72 L = 2.66 atm

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explanation: