Question

A 5 litre container holds helium at a temperature of 25 ◦C and a pressure of 2 atm. Determine the mass of gas in the container, the number of moles, and the number of particles.

Answer 1

Step-by-step explanation:

Given:

M = 2·10⁻³ kg/mol

V = 5 litre = 5·10⁻³ m³

t = 25°C; T = 273 + 25 = 298 K

p = 2 atm = 2·10⁵ Pa

Na = 6.02·10⁻²³ mol⁻¹

_____________________

m - ?

ν - ?

N - ?

p·V = m·R·T / M

1)

m=p·V·M / (R·T)=2·10⁵·5·10⁻³·2·10⁻³/ (8.31·298) ≈ 0.8·10⁻³ kg or m = 0.8 g

2)

ν = m /M = 0.8·10⁻³ / 2·10⁻³ = 0.4 mol

3)

N = ν·Na = 0.5·6.02·10⁻²³ ≈ 3·10⁻²³