The mass of hydrogen gas in the vessel is 2 g. How many hydrogen molecules are in the vessel?

Problem data: m (mass of hydrogen gas) = 2 g.

Reference values: M (molar mass of hydrogen) = 2.016 g / mol (≈ 2 g / mol); Na (Avogadro’s number) = 6.02 * 10 ^ 23 mol-1.

The number of molecules of gaseous hydrogen in a vessel can be determined from the equality: N / Na = ν (amount of substance) = m / M, whence N = m * Na / M.

Let’s perform the calculation: N = 2 * 6.02 * 10 ^ 23/2 = 6.02 * 10 ^ 23 molecules.

Answer: The vessel contains 6.02 * 10 ^ 23 molecules of hydrogen gas.