How many grams of water are required to produce 5.50L of hydrogen gas at 25.0 degrees C and 755mmHg?

Answer is: 4.02 grams of water are required.
Chemical reaction: BaH₂ + 2H₂O → Ba(OH)₂ + 2H₂.
Ideal gas law: p·V = n·R·T.
p = 755 mm Hg ÷ 760.0 mmHg / atm = 0.993 atm.
T = 25 + 273.15 = 298.15 K.
V(H₂) = 5.50 L.
R = 0,08206 L·atm/mol·K.
n(H₂) = 0.993 atm · 5.5 L ÷ 0,08206 L·atm/mol·K · 298.15 K.
n(H₂) = 0.223 mol.
From chemical reaction: n(H₂O) : n(H₂) = 1 : 1.
n(H₂O) = 0.223 mol.
m(H₂O) = 0.223 mol · 18 g/mol.
m(H₂O) = 4.02 g.

High-energy and unstable.

Green is technically every other color but green but the other wavelengths of the other colors get absorbed by the object and the wavelength of the color green gets reflected