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    Idenify the R.A.M. of a metal X form the following data: 1.0g of the anhydrous carbonate X2CO3 was added to 50cm3 of hydrochloric acid of concentration 1.0moldm3. The remaining acid after reaction was complete required 30.0cm3 of 1.0moldm3 sodium hydroxide for neutralisation.
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    (Original post by 15076683)
    Idenify the R.A.M. of a metal X form the following data: 1.0g of the anhydrous carbonate X2CO3 was added to 50cm3 of hydrochloric acid of concentration 1.0moldm3. The remaining acid after reaction was complete required 30.0cm3 of 1.0moldm3 sodium hydroxide for neutralisation.
    Hello,

    Firstly, you should begin by calculating the volume of HCl required in the neutralisation reaction; if you know the volume and concentration of the NaOH, you can calculate the number of moles which react (the number of moles of HCl is the same if you look at the reaction equation). You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.

    Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl, which is then used to calculate the number of moles of the X carbonate (once again using a chemical equation). Once this is known, the molar mass of the substance can be calculated. You can then take off the molar mass of the carbonate part of the formula to find the molar mass of the X2. It is then a simple case of diving by 2 to obtain the RAM of X.

    If anything has been unclear, please ask. I may even be kind enough to check your answer as well. ;-)
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    (Original post by Smithenator5000)
    Hello,

    Firstly, you should begin by calculating the volume of HCl required in the neutralisation reaction; if you know the volume and concentration of the NaOH, you can calculate the number of moles which react (the number of moles of HCl is the same if you look at the reaction equation). You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.

    Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl, which is then used to calculate the number of moles of the X carbonate (once again using a chemical equation). Once this is known, the molar mass of the substance can be calculated. You can then take off the molar mass of the carbonate part of the formula to find the molar mass of the X2. It is then a simple case of diving by 2 to obtain the RAM of X.

    If anything has been unclear, please ask. I may even be kind enough to check your answer as well. ;-)
    "You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl"

    Thanks for the help! Much appreciated. However, I'm still unsure on this bit. Surely to find the moles you divide it by the concentration??(it doesnt really matter anyway because the value is 1)

    Also, how can you use the new value to work out the reacting volume when I thought we already have that value: 50cm3

    When i tried the calculation, I came to an Mr of 0.002 so i assume I've done it completely wrong
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    (Original post by 15076683)
    "You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl"

    Thanks for the help! Much appreciated. However, I'm still unsure on this bit. Surely to find the moles you divide it by the concentration??(it doesnt really matter anyway because the value is 1)

    Also, how can you use the new value to work out the reacting volume when I thought we already have that value: 50cm3

    When i tried the calculation, I came to an Mr of 0.002 so i assume I've done it completely wrong
    Hello again,

    Sorry to keep you waiting. As for your first query, as concentration C = n/V,
    n = CV

    As for your second query, I think that you've fallen for the question's little trap. The 50cm3 of HCl was in excess, thus meaning some was left over. You therefore need to calculate how much was in the second reaction and then take that off the total acid volume to find the volume which reacted with 1.0g of the carbonate.

    Your final answer is rather strange as I'm sure you've noticed. I may write a full working for you, but I may be some time.

    Good luck :-).

    PS: sorry if my first reply was confusing- it had been a long day.
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    (Original post by Smithenator5000)
    Hello again,

    Sorry to keep you waiting. As for your first query, as concentration C = n/V,
    n = CV

    As for your second query, I think that you've fallen for the question's little trap. The 50cm3 of HCl was in excess, thus meaning some was left over. You therefore need to calculate how much was in the second reaction and then take that off the total acid volume to find the volume which reacted with 1.0g of the carbonate.

    Your final answer is rather strange as I'm sure you've noticed. I may write a full working for you, but I may be some time.

    Good luck :-).

    PS: sorry if my first reply was confusing- it had been a long day.
    Hmmm. This doesnt seem to be coming easy to me. Still a bit stuck despite your excellent help. This is what I've managed to do so far:

    Moles of NaOH = 0.03*1 = 0.03moles
    (2nd reaction) Moles of HCl = 0.03
    (1st reaction) Moles of HCl = 0.05*1 = 0.05 moles

    0.05-0.03=0.02moles

    moles of X2CO3 = 0.02/2 = 0.01

    That's where I'm to and now have no clue what to do!

    If possible, and I understand you have a life, could you push me in the right direction please. I find these so tricky

    Thanks for all your help!
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    (Original post by 15076683)
    Hmmm. This doesnt seem to be coming easy to me. Still a bit stuck despite your excellent help. This is what I've managed to do so far:

    Moles of NaOH = 0.03*1 = 0.03moles
    (2nd reaction) Moles of HCl = 0.03
    (1st reaction) Moles of HCl = 0.05*1 = 0.05 moles

    0.05-0.03=0.02moles

    moles of X2CO3 = 0.02/2 = 0.01

    That's where I'm to and now have no clue what to do!

    If possible, and I understand you have a life, could you push me in the right direction please. I find these so tricky

    Thanks for all your help!
    Hello,

    I have attached a full walk-through of the problem in PDF format. It may not be terribly clear, as it has been somewhat rushed with a busy schedule. It returns an odd answer still, so perhaps there is a fault in the question. That being said, I have been known to make errors. You may be able to spot the if they're there. If you have any more questions, please do not hesitate to ask.

    PS: sorry, there are a few mistakes in regard to notation on the attachment. Please ask if anything is unclear.
    Attached Images
  1. File Type: pdf Titration Calculation Walkthrough.pdf (285.6 KB, 107 views)
 
 
 
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