Join TSR now and get all your revision questions answeredSign up now
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hi I really needed help with this question I just dont know where to start?

    Ammonium iron (II) sulphate crystals have the following formula:
    (NH4)2SO4.FeSO4.nH2O. In an experiment to determine n, 8.492g of the salt were dissolved and made up to 250 cm3 of solution with distilled water and dilute sulphuric acid. A 25 cm3 portion of the solution was further acidified and titrated against potassium manganate (VII) solution of concentration 0.0150 moldm-3. A volume of 22.5 cm3 was required. Determine n.


    :confused::confused::eek:
    • Thread Starter
    Offline

    0
    ReputationRep:
    hi im stuck on this question and I dont know where to start?

    Ammonium iron (II) sulphate crystals have the following formula:
    (NH4)2SO4.FeSO4.nH2O. In an experiment to determine n, 8.492g of the salt were dissolved and made up to 250 cm3 of solution with distilled water and dilute sulphuric acid. A 25 cm3 portion of the solution was further acidified and titrated against potassium manganate (VII) solution of concentration 0.0150 moldm-3. A volume of 22.5 cm3 was required. Determine n.

    any ideas? :confused:
    • Community Assistant
    • Study Helper
    Offline

    14
    ReputationRep:
    (Original post by amarjit700)
    Hi I really needed help with this question I just dont know where to start?

    Ammonium iron (II) sulphate crystals have the following formula:
    (NH4)2SO4.FeSO4.nH2O. In an experiment to determine n, 8.492g of the salt were dissolved and made up to 250 cm3 of solution with distilled water and dilute sulphuric acid. A 25 cm3 portion of the solution was further acidified and titrated against potassium manganate (VII) solution of concentration 0.0150 moldm-3. A volume of 22.5 cm3 was required. Determine n.


    :confused::confused::eek:
    step 1: write out the equation for the reaction of manganate(VII) ions with iron(II) ions

    step 2: calculate the moles of manganate ions in the titre.

    step 3: Use step 1 & 2 to find the moles of iron(II) ions in the titre.

    step 4: consider how many moles of iron ammonium sulphate come from each mole of iron(II)

    step 5: scale up step 4 to take into account that there was actually 250ml of solution not 25ml

    step 6: find the mass of step 5

    step 7: subtract the mass from step 6 from the actual mass used. The difference is the mass of water

    step 8: find the ratio of moles of iron(II) to water to get 'n'.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by charco)
    step 1: write out the equation for the reaction of manganate(VII) ions with iron(II) ions

    step 2: calculate the moles of manganate ions in the titre.

    step 3: Use step 1 & 2 to find the moles of iron(II) ions in the titre.

    step 4: consider how many moles of iron ammonium sulphate come from each mole of iron(II)

    step 5: scale up step 4 to take into account that there was actually 250ml of solution not 25ml

    step 6: find the mass of step 5

    step 7: subtract the mass from step 6 from the actual mass used. The difference is the mass of water

    step 8: find the ratio of moles of iron(II) to water to get 'n'.
    thank you so much!!! I really appreciate it
 
 
 
Poll
If you won £30,000, which of these would you spend it on?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.