If oxygen is present in one litre flask at pressure of 7.6 × 10-10 mm

1.	If oxygen is present in one litre flask at pressure of 7.6 × 10-10 mm Hg, then the number of oxygen molecules in theflask at 0 C will beA) 27 x 1010B) 0.27 × 1010C) 0.027 x 1010D) 2.7 x 1010
Answer» First we should calculate the number of moles of the gas under the given condition by the relation PV = nRT Here P = 7.6 * 10-10 mm Hg = 7.6 10-10/760 atm. = 1 10-12 atm. V = 1 litre T = 273 + 0 = 273K R = 0.082 litre atm./K/mol Putting the values in equation n = PV/RT = 1 10^{-12} 1/0.082 273 moles now since 1 mole = 6.023 1023 molecules 10^{-12}/0.082 273 moles = 6.023 1023 10^{-12}/0.082 273 molecules = 2.7 * 10^10 molecules

If oxygen is present in one litre flask at pressure of 7.6 × 10-10 mm Hg, then the number of oxygen molecules in theflask at 0 C will beA) 27 x 1010B) 0.27 × 1010C) 0.027 x 1010D) 2.7 x 1010

Answer»

First we should calculate the number of moles of the gas under the given condition by the relation

PV = nRT

Here P = 7.6 * 10-10 mm Hg

= 7.6 *10-10/760 atm.

= 1 * 10-12 atm.

V = 1 litre

T = 273 + 0 = 273K

R = 0.082 litre atm./K/mol

Putting the values in equation

n = PV/RT

= 1 *10^{-12} *1/0.082 *273 moles

now since 1 mole = 6.023 * 1023 molecules

10^{-12}/0.082 *273 moles = 6.023 *1023 *10^{-12}/0.082 *273 molecules

= 2.7 * 10^10 molecules