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What is the concentration in moles dm^-3 of ... Watch

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    What is the concentration in moles dm^-3 of ...
    10g of FeSO4.(NH4)2SO4.6H20 in 250cm^3 of solution?
    for this one i did 10g /392(molar mass) = 0.03 mole
    so there 0.03 mole of FeSO4.(NH4)2SO4.6H2O in 0.25dm^3 of solution
    so 0.03/0.25 = 0.12mol.dm^-3
    is that right?

    What is the concentration in moles dm^-3 of ...
    240cm^3 of NH3(g) dissolved in 1000cm^3 of solution ?

    i worked out the mass of NH3 which is 17
    and i need to find out how many moles of NH3 in 240cm^3,
    do i need to convert the 240cm^3 into grams? how?
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    (Original post by Chez 01)
    What is the concentration in moles dm^-3 of ...
    10g of FeSO4.(NH4)2SO4.6H20 in 250cm^3 of solution?
    for this one i did 10g /392(molar mass) = 0.03 mole
    so there 0.03 mole of FeSO4.(NH4)2SO4.6H2O in 0.25dm^3 of solution
    so 0.03/0.25 = 0.12mol.dm^-3
    is that right?

    What is the concentration in moles dm^-3 of ...
    240cm^3 of NH3(g) dissolved in 1000cm^3 of solution ?

    i worked out the mass of NH3 which is 17
    and i need to find out how many moles of NH3 in 240cm^3,
    do i need to convert the 240cm^3 into grams? how?
    For the first question your process is spot on.
    For the ammonia solution you nees to consider the volume of 1 mole of gas at rtp is 24dm3 - so how many moles in 240cm3?
    You don't nees to consider mass.
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    1 don't think 10/392 = 0.03.

    You know I mole of any gas at STP is 24dm3
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    (Original post by TutorsChemistry)
    For the first question your process is spot on.
    For the ammonia solution you nees to consider the volume of 1 mole of gas at rtp is 24dm3 - so how many moles in 240cm3?
    You don't nees to consider mass.
    thankyou

    so is this right ?
    240/17=14mole
    so theres 14 mole of NH3 dissoled in 1dm^3 of solution
    so 14/1 = 14 mol.dm^-3
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    (Original post by Maker)
    1 don't think 10/392 = 0.03.

    You know I mole of any gas at STP is 24dm3
    10/392 when rounded is o.03
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    (Original post by Chez 01)
    thankyou

    so is this right ?
    240/17=14mole
    so theres 14 mole of NH3 dissoled in 1dm^3 of solution
    so 14/1 = 14 mol.dm^-3
    Sorry no.
    The moles is 240cm3/24000cm3 =0.01 moles.
    When calculating moles of gas from its volume you dont need the molar mass
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    (Original post by Chez 01)
    10/392 when rounded is o.03
    It is.
    I believe Maker is questioning how many sf you should use.
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    (Original post by TutorsChemistry)
    Sorry no.
    The moles is 240cm3/24000cm3 =0.01 moles.
    When calculating moles of gas from its volume you dont need the molar mass
    I'm not understanding, could you explain how id calculate the concentration in this example please
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    First you need to use the fact that 1 mole of any gas at 298K and 1 atm pressure occupies 24.0 dm3 (or 24000 cm3).

    The volume of gas you have used was 240cm3. Hence you have used 240/24000 moles.

    When using VOLUME of a gas to calculate moles, you must use molar volume.
    Don't try to use molar mass or convert into mass.

    When given the MASS, even of a gas, use the molar mass to calculate moles.
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    (Original post by Chez 01)
    10/392 when rounded is o.03
    More like 0.025
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    (Original post by TutorsChemistry)
    First you need to use the fact that 1 mole of any gas at 298K and 1 atm pressure occupies 24.0 dm3 (or 24000 cm3).

    The volume of gas you have used was 240cm3. Hence you have used 240/24000 moles.

    When using VOLUME of a gas to calculate moles, you must use molar volume.
    Don't try to use molar mass or convert into mass.

    When given the MASS, even of a gas, use the molar mass to calculate moles.
    so how do i calculate the molar volume
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    PV=nRT
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    (Original post by Chez 01)
    so how do i calculate the molar volume
    Molar volume of a gas is 24dm3 (at 298K and 1 atm.)
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    (Original post by TutorsChemistry)
    Molar volume of a gas is 24dm3 (at 298K and 1 atm.)
    so would this be right
    240/1000 = 0.24dm3
    0.24dm3/24=0.01moles
    0.01=1=0.01mol.dm-3
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    (Original post by Chez 01)
    so would this be right
    240/1000 = 0.24dm3
    0.24dm3/24=0.01moles
    0.01=1=0.01mol.dm-3
    Yes, spot on.
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    (Original post by TutorsChemistry)
    Yes, spot on.
    thankyou
 
 
 
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