# Calculate the mass of 2 mol of hydrogen gas and the number of molecules in this amount of substance.

Answer: m = 4 g; N = 1.2 * 10 ^ 24 molecules.
Explanation of the solution to the problem: to solve this problem, you must use the following formulas:
N = Na * n, where N is the number of molecules of a given substance, Na is purely Avagadro (the value is constant and equal to: Na = 6.02 * 10 ^ 23 mol ^ -1), n ​​is the amount of substance of the given compound, mol.
The mass of a substance is determined by the formula:
m = n * M, where m is the mass of the substance, g; M is the molar mass of the substance, M (H2) = 2 g / mol (found according to the system of chemical elements of DI Mendeleev).
Substituting into the formulas the values ​​known from the condition of the problem, we obtain:
m = n * M = 2 * 2 = 4 g.
N = Na * n = 6.02 * 10 ^ 23 * 2 = 1.2 * 10 ^ 24 molecules.

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