How many molecules of hydrogen gas are present in a 750 ml

container at STP?

Answer: 1.99 x 10²² molecules H2

Explanation:First we will solve for the moles of H2 using Ideal gas law PV = nRT then derive for moles (n).

At STP, pressure is equal to 1 atm and Temperature is 273 K.

Convert volume in mL to L:

750 mL x 1 L / 1000 mL

= 0.75 mL

n = PV / RT

= 1 atm (0.75 L) / 0.0821 L. atm / mole. K (273 K)

= 3.3x10-² moles H2

Convert moles of H2 to atoms using Avogadro's Number.

3.3x10-² moles H2 / 6.022x10²³ atoms H2 / 1 mole H2

= 1.99x10²² atoms H2