The mass of one molecule of hydrogen can be calculated by dividing the total mass of hydrogen (1 gram) by Avogadro's number (6.022 x 10^23). This gives us a mass of approximately 1.661 x 10^-24 grams per molecule.

Next, we can calculate the number of molecules present in 4 liters of hydrogen by first converting the volume to cubic meters (4 liters = 0.004 cubic meters). Then, we can use the ideal gas law (PV = nRT) to calculate the number of moles of hydrogen present in the container. Since the container is at standard temperature and pressure (0˚C and 1 atm), we can use the ideal gas constant (R = 0.08206 L atm/mol K) to solve for n (moles of hydrogen). This gives us a value of approximately 0.00163 moles of hydrogen in the container.

Since one mole of a substance contains Avogadro's number of molecules, we can simply multiply our moles of hydrogen by Avogadro's number to calculate the total number of molecules in the container. This gives us a total of approximately 9.84 x 10^20 molecules of hydrogen in 4 liters.

To calculate the amount of substance present in the container, we can use the formula n = m/M, where n is the amount of substance in moles, m is the mass of the substance in grams, and M is the molar mass of the substance in grams per mole. In this case, n (amount of substance) is equal to our previously calculated value of 0.00163 moles, m (mass of hydrogen) is equal to 1 gram, and M (molar mass of hydrogen) is equal to 2 grams per mole. Therefore, the amount of substance in the container is 0.00163 moles of hydrogen.

Finally, to calculate the concentration of molecules in the container, we can use the formula C = n/V, where C is the concentration in moles per cubic meter, n is the amount of substance in moles, and V is the volume in cubic meters. In this case, n (amount of substance) is equal to 0.00163 moles, and V (volume) is equal to 0.004 cubic meters. Therefore, the concentration of molecules in the container is approximately 4.075 x 10^-4 moles per cubic meter.