Use the ideal gas equation
#P*V = n * R*T#
Where:
#P -> " is the pressure expressed in " atm#
#V -> " is the volume occupied by the gas expressed in "L #
#n-> " is the number of moles of the gas"#
# R ->" is the universal gas constant" =0.0821 \ L* atm*mol^-1 *K^-1#
# T -> " is the kelvin temperature "#
#-----------------#
# S.T.P "conditions" => T = 273 K and P= 1.00 \ atm#
Rearrange the formula and solve for V.
# V = (n * R*T)/P#
Find the number of moles of the hydrogen gas present in the 16 grams.
#n_(H_2)= 16 \ g \ H_2xx(1 \ mol. H_2)/(2.016\ g \ H_2)#
#n_(H_2)~=7.9 \ mol.#
#V=(7.9 \ mol. xx 0.0821 \ L* atm*mol^-1 *K^-1xx 273 \ K)/ (1.00 \ atm)#
#V=(7.9 \ cancel(mol.) xx 0.0821 \ L* cancel(atm)*cancel(mol^-1)*cancel(K^-1)xx 273 \ cancel(K))/ (1.00 \ cancel(atm))#
#V~=1.8xx10^2\ L#
#--------------------#
A quick approach
At S.T.P you can use the following formula:
# n_(H_2)= V/V_M#
# n_(H_2) " is the number of moles of the gas." #
#V " is Volume of the gas under S.T.P conditions"#
# V_M" is the molar volume i.e the volume occupied by 1 mole of "#
# "any gas under S.T.P conditions, equal to 22.4 L/mol."#
#n_(H_2)= 16 \ g \ H_2xx(1 \ mol. H_2)/(2.016\ g \ H_2)#
#n_(H_2)~=7.9 \ mol.#
# V = n_(H_2)xxV_M#
# V = 7.9 \ mol xx 22.4 L* mol^-1#
#V~=1.8xx10^2\ L#
