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Given a 10.0g sample of MgCO3*5H2O, what weight of anhydrous magnesium carbonate can be obtained after driving off the water?

  • Chemistry -

    wait.. that can't be right.

  • Chemistry -

    no i don't think the weight will be increasing after getting rid of the water.

    work out the molar mass of hydrated magnesium carbonate, then find the ratio of water to the whole thing in regard to molar mass
    M(MgCO3*5H20)= 144
    M(5H2O) = 70
    ratio = 70/144 = 0.486

    this means that 48.6% of that 10grams is water

    so by multiplying the 10grams by .486 we get the mass of water, then subtract from 10grams to get the mass of magnesium carbonate once the water has been removed

    the ratio bit may be a bit vague, if it doesn't make sense just say so and I'll try and clear it up

  • Chemistry -

    apologies M(MgCO3*5H20) = 154
    ratio = 70/154 = 0.4545
    so 45.5% is water, same process as above just use this value instead

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