The pressure of 1.95 moles of oxygen that occupies 22.3 liters at 62 °C is ____ atmospheres. Enter your answer rounded to the proper number of significant figures?

Answer 1

The ideal gas law relates the pressure (P), volume (V), temperature (T), and moles of a gas (n) through the ideal gas equation

PV = nRT

where R is the ideal gas constant

You can find R, the ideal gas constant, with a variety of units. To minimize the number of conversions you have to do, pick the R value with the most similar units. For example,

R = 0.082057 (L*atm)/(K*mol)

Notice that this R has units of Kelvin. Convert the Celsius temperature to Kelvin by adding 273.15

62 + 273.15 = 335.15 K

Now to find the pressure based on the ideal gas law, divide both sides of the equation by the volume

P = (nRT)/V

Plug in the given values into the equation

P = (1.95 moles)(0.082057 (L*atm)/(K*mol))(335.15 K)/(22.3 L)

P = 2.4048 atm

To maintain the proper number of significant figures, remember when multiplying or dividing, the least number of significant figures of any component in the equation determines the number in the answer. In this case, the least number of significant figures is 3, so the answer must also have 3 significant figures. Therefore,

P = 2.40 atm