# MCQ help

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#1
Can someone help with this question?
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3 years ago
#2
First off, I would ignore the x1 parts as the question is much simpler without them.
Imagine the situation where you start with 1mol of steam. 20% has dissociated, so you are left with 0.8mol of steam, 0.2mol of hydrogen, and 0.1mol of oxygen. This means that the mole fractions, and therefore the partial pressures, must be in an 8 1 ratio.

To work out mole fraction, you would divide the number of moles of the specific molecule by the total number of moles. In this case the total number of moles is 0.8+0.2+0.1=1.1, so you would have to divide it by 1.1.
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#3
(Original post by lizardlizard)
First off, I would ignore the x1 parts as the question is much simpler without them.
Imagine the situation where you start with 1mol of steam. 20% has dissociated, so you are left with 0.8mol of steam, 0.2mol of hydrogen, and 0.1mol of oxygen. This means that the mole fractions, and therefore the partial pressures, must be in an 8 1 ratio.

To work out mole fraction, you would divide the number of moles of the specific molecule by the total number of moles. In this case the total number of moles is 0.8+0.2+0.1=1.1, so you would have to divide it by 1.1.
thank you!!
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