B because....................
I am assuming you are talking about Neon. The rate of diffusion is directly proportional to the molar mass of the gas. Since neon has a molar mass of 20.18 grams, the gas must have a lower molar mass and must be a gas at 273 Kelvin. There are several elements that fulfill this criteria: Hydrogen, Helium, Oxygen, Nitrogen, and Fluorine.
ANSWER
36.12 degrees fahrenheit
There’s no formula that relates solubility to temperature, but you can look up the solubility constant Ksp of substance given and then take the square root of that to find solubility.
The balanced equation would be (1)BaCl2 + (1)H2SO4 --> (1)BaSO4 + (2)HCl2
Then you should know that the coefficients stand for moles.
The thing is I'm not sure if H2SO4 is 35 ml or .200 m.
Also, is this topic stoichiometry?