How many moles of Helium gas are in a balloon with a volume of 6.452 L at 99.7 kPa
and 297 Kelvin

n = 0.26 mol.

Explanation:

Given,

Pressure, P = 99.7 kPa = 1 atm

where 101.325 kPa  = 1 atm

            P = 0.984 atm

Temperature, T = 297 K

Volume = 6.452 L

Now, using ideal gas equation

PV = n RT

0.984 x 6.452 = n x 0.08206 x 297

n = 0.26 mol.

c is the answer because when something is left after something evaporates that shows the chemical change.