Answer:
B.) 2.92
Explanation:
Tp find the mass of H₂ produced, you need to (1) convert grams AlCl₃ to moles AlCl₃ (via molar mass), then (2) convert moles AlCl₃ to moles H₂ (via mole-to-mole ratio from equation coefficients), and then (3) convert moles H₂ to grams H₂ (via molar mass). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units.
Molar Mass (AlCl₃): 26.982 g/mol + 3(35.453 g/mol)
Molar Mass (AlCl₃): 133.341 g/mol
2 Al + 6 HCl ---> 2 AlCl₃ + 3 H₂
Molar Mass (H₂): 2(1.008 g/mol)
Molar Mass (H₂): 2.016 g/mol
129 g AlCl₃ 1 mole 3 moles H₂ 2.016 g
------------------ x ------------------ x --------------------- x --------------- =
133.341 g 2 moles AlCl₃ 1 mole
= 2.93 g H₂
*our answers are most likely different due to using slightly different molar masses
In reality closed systems do not exist. In the theoretical case of a closed system the total energy of the system would stay the same (matter and particles are considered energy to). More important: the energy level throughout the whole system will eventually be evenly spread and uniform (entropy), therefore no energy differential is left to perform work.