Use the ideal gas equation to solve for moles (n):
PV = nRT
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P = 10 torr (convert to atm) = (10 torr)(1atm / 760 torr) = 0.0132 atm
V = 1 L
n = moles of sodium
R = universal gas constant = 0.08205 L.atm/mol.K
T = 1000 deg C (convert to Kelvin by adding 273) = 1273 K
Manipulate the ideal gas equation to come up with formula for n:
n = PV / RT = (0.0132 atm x 1 L) / (0.08205 L.atm/mol.K)(1273 K)
n = 1.26 x 10^ -4 moles
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# of sodium atoms = n x Avogadro's number
# of sodium atoms = (1.26 x 10^ -4 moles)(6.023 x 10^ 23 atoms / mole)
# of sodium atoms = 7.6 x 10^ 19 atoms ===> answ
