2012 Destroyer GC #204 question

[Illfavor]

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At 0 degrees C a gas is dissolved in water at a mole fraction of 2x10^-18. What is the molality of this solution given the molecular weight of the gas is 32g/mole.

Mole fraction = moles solute/moles total. In his answer he sorta ignores the "moles total" part and just assumes it's 1 mol of water. I'm confused, since the total moles includes the moles of gas. Are we ignoring it because it's so small?

To find molality shouldn't it be moles gas/ mass of (total moles - moles gas)

 

[Intent]

At 0 degrees C a gas is dissolved in water at a mole fraction of 2x10^-18. What is the molality of this solution given the molecular weight of the gas is 32g/mole.

Mole fraction = moles solute/moles total. In his answer he sorta ignores the "moles total" part and just assumes it's 1 mol of water. I'm confused, since the total moles includes the moles of gas. Are we ignoring it because it's so small?

To find molality shouldn't it be moles gas/ mass of (total moles - moles gas)

Hi, I took Romano's class and he had us cross out this problem just thought I'd let you know

 

[invictus1]

Who is Romano?

 

[cmF]

Who is Romano?

He's the professor that wrote DAT Destroyer and teaches a DAT prep course as well.