Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    14
    Okay, can someone actually explain to me the basics of titration. Please explain as simply as you can the method.

    Then, can you tell me if it is usually acid that is the Unknown. And the for Unknown you find out the moles? Am I correct in thinking so?

    Finally, there is always a known in which you can find out the number of moles. Then you use stoichiometry to find out the moles in the Unknown. (do you always use stoichoimetry? And if so why?)This will help find either concentration or volume (depends on which your given) . Is this correct?
    • Thread Starter
    Offline

    14
    Name:  image.jpg
Views: 69
Size:  542.8 KBAttachment 511881511883
    Attached Images
     
    Offline

    3
    ReputationRep:
    You've calculated the mol in 25cm^3, not in 250cm^3. This is important because the mass (1.96g) corresponds with 250cm^3.

    What must you do now?

    Then, remember to subtract the molar mass of (OH)2.
    Offline

    1
    ReputationRep:
    I think you've got the general idea basically, what you are doing is filling a burette with a solution of known concentration, and running it into a conical flask filled with another solution (of known volume) and usually some sort of indicator. You run the burette solution into the other solution until a colour change (this is called the end point). As you get nearer the end point, you need to add the solution very slowly (one drop at a time) as you don't need a lot of it for the colour change. Once the colour has changed, you record the volume mark on the burette and use this to calculate the number of moles of burette solution (n=CV). There are different ways to do it, but one way is using stoichiometry, from the balanced equation find the mole ratio of the two solutions and use this to calculate the number of moles of the unknown solution and from this its concentration. You can also use the formula C1V1=C2V2, but try and stick with whichever method you've been taught. Hope that helps
    • Thread Starter
    Offline

    14
    (Original post by Bath_Student)
    You've calculated the mol in 25cm^3, not in 250cm^3. This is important because the mass (1.96g) corresponds with 250cm^3.

    What must you do now?

    Then, remember to subtract the molar mass of (OH)2.
    You multiply the moles by 10 and find the mass. Answer is calcium right? (39.962)
    Offline

    3
    ReputationRep:
    (Original post by Questioness)
    You multiply the moles by 10 and find the mass. Answer is calcium right? (39.962)
    All correct!
    • Thread Starter
    Offline

    14
    (Original post by Bath_Student)
    All correct!
    Thanks
    Offline

    1
    ReputationRep:
    Okay, so to do a titration, you want to find out the concentration of an unknown right? This could be a base or an acid, it just depends. Anyway, let's say your unknown is a hydrochloric acid, so, to find out the concentration, you need to titrate it against a base of known concentration, lets say we use NaOH at 1 mol/l, against a known volume of hydrochloric acid, say 25ml.
    You need to do the titrations at least 3 times, until you get concordant results (within 0.1ml of each other).

    Next, we take the average volume of NaOH from the titrations (don't use the first titration, that's just a practice, only use the two that are concordant to get the average), lets say it's 12.15ml, we use N=CV to work out the number of moles needed to neutralise the hydrochloric acid (remeber v is in litres).
    From the number of moles we get, which in this example would be:
    n=1x0.01215=0.01215 moles

    We use the mole ration from the balanced equation, which for this reaction 1 mole NaOH gives you 1 Mole HCl, we can work out the concentration as 0.001215 moles of NaOH will react with 0.01215 moles of HCl, so;
    concentration of hydrochloric acid= n/v
    =0.01215/0.025 = 0.486 mol/l
    Offline

    3
    ReputationRep:
    (Original post by Pheonixfeather3)
    Okay, so to do a titration, you want to find out the concentration of an unknown right? This could be a base or an acid, it just depends. Anyway, let's say your unknown is a hydrochloric acid, so, to find out the concentration, you need to titrate it against a base of known concentration, lets say we use NaOH at 1 mol/l, against a known volume of hydrochloric acid, say 25ml.
    You need to do the titrations at least 3 times, until you get concordant results (within 0.1ml of each other).

    Next, we take the average volume of NaOH from the titrations (don't use the first titration, that's just a practice, only use the two that are concordant to get the average), lets say it's 12.15ml, we use N=CV to work out the number of moles needed to neutralise the hydrochloric acid (remeber v is in litres).
    From the number of moles we get, which in this example would be:
    n=1x0.01215=0.01215 moles

    We use the mole ration from the balanced equation, which for this reaction 1 mole NaOH gives you 1 Mole HCl, we can work out the concentration as 0.001215 moles of NaOH will react with 0.01215 moles of HCl, so;
    concentration of hydrochloric acid= n/v
    =0.01215/0.025 = 0.486 mol/l
    Lay off the drugs
    • Thread Starter
    Offline

    14
    (Original post by Pheonixfeather3)
    Okay, so to do a titration, you want to find out the concentration of an unknown right? This could be a base or an acid, it just depends. Anyway, let's say your unknown is a hydrochloric acid, so, to find out the concentration, you need to titrate it against a base of known concentration, lets say we use NaOH at 1 mol/l, against a known volume of hydrochloric acid, say 25ml.
    You need to do the titrations at least 3 times, until you get concordant results (within 0.1ml of each other).

    Next, we take the average volume of NaOH from the titrations (don't use the first titration, that's just a practice, only use the two that are concordant to get the average), lets say it's 12.15ml, we use N=CV to work out the number of moles needed to neutralise the hydrochloric acid (remeber v is in litres).
    From the number of moles we get, which in this example would be:
    n=1x0.01215=0.01215 moles

    We use the mole ration from the balanced equation, which for this reaction 1 mole NaOH gives you 1 Mole HCl, we can work out the concentration as 0.001215 moles of NaOH will react with 0.01215 moles of HCl, so;
    concentration of hydrochloric acid= n/v
    =0.01215/0.025 = 0.486 mol/l
    Thanks, you explained it really well. I understand it a lot better now. But why is the volume in litres( shouldn't it be dm^3)?
    Offline

    3
    ReputationRep:
    (Original post by Questioness)
    Thanks, you explained it really well. I understand it a lot better now. But why is the volume in litres( shouldn't it be dm^3)?
    1 L = 1dm3
    • Thread Starter
    Offline

    14
    (Original post by Bath_Student)
    1 L = 1dm3
    Ahh, alright. Thanks again.
    Offline

    1
    ReputationRep:
    (Original post by Bath_Student)
    Lay off the drugs
    ?????
    Offline

    16
    ReputationRep:
    (Original post by Questioness)
    Okay, can someone actually explain to me the basics of titration. Please explain as simply as you can the method.

    Then, can you tell me if it is usually acid that is the Unknown. And the for Unknown you find out the moles? Am I correct in thinking so?

    Finally, there is always a known in which you can find out the number of moles. Then you use stoichiometry to find out the moles in the Unknown. (do you always use stoichoimetry? And if so why?)This will help find either concentration or volume (depends on which your given) . Is this correct?
    C1 x V1 = C2 x V2
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    What's your favourite Christmas sweets?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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.