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    Attachment 527339527341Name:  image.jpg
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Size:  503.4 KBSo I've worked out what the precipitate is Fe(OH)3 but I don't get how to work out the gas is oxygen using a calculation?
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    Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

    You can also find the Exam Thread list for A-levels here and GCSE here. :dumbells:


    Just quoting in Puddles the Monkey so she can move the thread if needed
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    Anyone pls
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    You know that the density is 1.333x10^-3 grams for every cm^3.
    The mass can then be calculated by multiplying this by 24000 because 1 mol of gas occupies 24000cm3.
    This gives you 31.992g in 1 mol, or in other words 31.992g.mol^-1. This is the same units as Mr so it is very likely given the context that the gas is O2. (sorry dunno how to do subscripts etc lol)
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    Okay, so you need to find the Mr to prove that the gas released is oxygen. You have the density which is 1.333*10-3, density is the mass over the volume right okay

    the gas is released at room temperature and pressure which means that number of moles= V of gas / 24000

    number of moles= mass/Mr , okay so mass= number of moles*Mr

    Substitute these two equations into the density formula, so denisty= (mass) number of moles*Mr / (volume) number of moles*24000, number of moles cancel each other so you're left with Mr/2400=density ................... so Mr/2400= 1.333*10-3 which equals 32 which equals the Mr of oxygen
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    AqsaMx Heya, I've popped this in Chemistry for you
 
 
 
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