The volume of a sample of hydrogen is 771.8 mL and it exerts 638.7 mm Hg pressure at 6.5 ºC. What volume does it occupy at standard temperature and pressure? Select one: a. 653 b. 2.73e4 c. 664 d. 861

627mL (May be something is wrong with the choices)

Explanation:

First step: Ideal gas Law to get the moles

P. V = n. R. T

where P is pressure in atm (638.7 mmHg)

V is volume in L

n, the number of moles, the unknow value at this time

R the Ideal gas constant 0.082 L. atm/mol. K

T, the temperature in K (°C + 273)

760 mmHg ___ 1 atm

638.7 mmHg ___ (638.7 / 760) = 0.84 atm

771,8 mL / 1000 = 0.7718 L

6.5°C + 273 = 279.5 K

0.7718 L. 0.84atm = n. 0.082 L. atm/mol. K. 279.5K

0.7718 L. 0.84atm / 0.082 mol. K/L. atm. 279.5K = n

0,028 moles = n

Standard temperature and pressure are 273K and 1 atm

1 atm. Volume = 0,028 moles. 0.082 L. atm/mol. K. 273K

Volume = (0,028 moles. 0.082 L. atm/mol. K. 273K) / 1atm

Volume = 0,6268 L = 627mL