No, the elements are not always transparent.
<u>Explanation:</u>
The elements become transparent when the light passes through those elements. Transparency is caused because of the transmission and the passing of the light waves through these elements.
But the metals do not become transparent even when the light waves pass through these metals. Metals do not become transparent because the refractive index in them is very big.
Hydrogen i suppose is the right one
Answer is: the partial pressure of the helium gas is 0.158 atm.
p(mixture) = 0.48 atm; total pressure.
m(H₂) = 1.0 g; mass of hydrogen gas.
n(H₂) = m(H₂) ÷ M(H₂).
n(H₂) = 1.0 g ÷ 2 g/mol.
n(H₂) = 0.5 mol; amount of hydrogen.
m(He) = 1.0 g; mass of helium.
n(He) = 1 g ÷ 4 g/mol.
n(He) = 0.25 mol; amount of helium.
χ(H₂) = 0.5 mol ÷ 0.75 mol.
χ(H₂) = 0.67; mole fraction of hydrogen.
χ(He) = 0.25 mol ÷ 0.75 mol.
χ(He) = 0.33; mole fraction of helium.
p(He) = 0.33 · 0.48 atm.
p(He) = 0.158 atm; the partial pressure of the helium gas.
