A sample of krypton gas collected at STP occupies a volume of 28.8 L. How many moles of gas does the sample contain?

To calculate the number of moles of krypton gas in the sample, we can use the ideal gas law equation:

PV = nRT

Where:
P = pressure (STP is 1 atm)
V = volume (28.8 L)
n = number of moles (what we want to find)
R = ideal gas constant (0.0821 L.atm/mol.K)
T = temperature (STP is 273 K)

Substitute the known values into the equation:

(1 atm)(28.8 L) = n(0.0821 L.atm/mol.K)(273 K)

28.8 = 22.3023n

n = 28.8 / 22.3023
n = 1.29 mol

Therefore, the sample of krypton gas contains 1.29 moles of gas.