A cylinder contains hydrogen gas at pressure of 249 kPa and temperature 27OC. Its density is :

To find the density of the hydrogen gas, we can use the ideal gas law equation, which is:

PV = nRT

Where: P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.

We want to find the density (ρ), which is mass/volume. We can express the number of moles (n) as mass (m) divided by molar mass (M), so the equation becomes:

PV = (m/M)RT

Rearranging for m/V (which is ρ), we get:

ρ = PM/RT

We know that: P = 249 kPa = 249,000 Pa (since 1 kPa = 1,000 Pa), R = 8.314 J/(mol·K) (the ideal gas constant), T = 27°C = 300.15 K (since you add 273.15 to convert from Celsius to Kelvin), and M = 2.016 g/mol (the molar mass of hydrogen).

Substituting these values into the equation, we get:

ρ = (249,000 Pa * 2.016 g/mol) / (8.314 J/(mol·K) * 300.15 K)

Solving this equation will give you the density of the hydrogen gas in the cylinder.