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    i am struggling on this question can you please help me

    25.0cm(cubed) of a solution containing 4.0g of sodium hydroxide per dm(cubed) were exactly neautralised by 20 cm(cubed) of a solution of sulfuric acid.

    a) calculate the concentration of the sodium hydroxide solution in mol per dm(cubed)
    (Ar values: Na=23,O=16,H=1)

    b) caluclate the no. of moles of sodium hydroxide in 25.0cm(cubed) of the solution

    c) write a balanced equation for the reaction

    d) calculate the no. of moles of sulfuric acid in 20cm(cubed) of solution

    e)calculate the no. of moles of sulfuric acid in mol per dm(cubed)

    i need to know how to do these type of questions for my gcses..... please help me guys ......... thanks..... also can you quote me as well....thanks
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    (Original post by thepastpaper)
    i am struggling on this question can you please help me

    25.0cm(cubed) of a solution containing 4.0g of sodium hydroxide per dm(cubed) were exactly neautralised by 20 cm(cubed) of a solution of sulfuric acid.

    a) calculate the concentration of the sodium hydroxide solution in mol per dm(cubed)
    (Ar values: Na=23,O=16,H=1)

    b) caluclate the no. of moles of sodium hydroxide in 25.0cm(cubed) of the solution

    c) write a balanced equation for the reaction

    d) calculate the no. of moles of sulfuric acid in 20cm(cubed) of solution

    e)calculate the no. of moles of sulfuric acid in mol per dm(cubed)

    i need to know how to do these type of questions for my gcses..... please help me guys ......... thanks..... also can you quote me as well....thanks
    well, do you know how to do any of it? We don't generally just provide complete answers straight off to multi-part questions. You should really post what you have done so far and we can help you from there.
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    (Original post by Plato's Trousers)
    well, do you know how to do any of it? We don't generally just provide complete answers straight off to multi-part questions. You should really post what you have done so far and we can help you from there.
    is the balanced formulae this..... 2NaOH+H2SO4----> Na2SO4+2H2O

    a) 23+16+1=40
    40 in 1000cm(cubed) of NaOH
    so 1cm(cubed)=40/1000
    so 25=40/100 times 25
    = 1 mol/dm(cubed) ? is the starting right i dont understand it....
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    (Original post by thepastpaper)
    is the balanced formulae this..... 2NaOH+H2SO4----> Na2SO4+2H2O
    yes
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    (Original post by Plato's Trousers)
    yes
    is a) right or not ?
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    (Original post by thepastpaper)
    is a) right or not ?
    sorry, the door bell went!

    not quite. formula weight is 40 as you say. So if 4g are in 1 dm3, that is 0.1M

    so in 25cm3 you will have 25/1000 x 0.1 moles of NaOH (=0.0025 moles)

    now from your balanced equation, you know that 2 moles of NaOH react with every mole of acid, so if you had 0.0025 moles of NaOH, you must have half as much acid.

    can you do the rest?
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    (Original post by Plato's Trousers)
    sorry, the door bell went!

    not quite. formula weight is 40 as you say. So if 4g are in 1 dm3, that is 0.1M

    so in 25cm3 you will have 25/1000 x 0.1 moles of NaOH (=0.0025 moles)
    i dont get how you get 0.1 moles from 'So if 4g are in 1 dm3, that is 0.1M' if the form weight is 40?
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    (Original post by thepastpaper)
    i dont get how you get 0.1 moles from 'So if 4g are in 1 dm3, that is 0.1M' if the form weight is 40?
    ok, 1 mole would be 40g - agree?

    4g is therefore 0.1 mole - agree?

    so 4g in 1 litre is 0.1 mole/litre which is 0.1M
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    (Original post by Plato's Trousers)
    ok, 1 mole would be 40g - agree?

    4g is therefore 0.1 mole - agree?

    so 4g in 1 litre is 0.1 mole/litre which is 0.1M
    oh thanks i get it now thanks for your time
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    (Original post by thepastpaper)
    oh thanks i get it now thanks for your time
    cool. so you are happy with it all now, yes?
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    (Original post by Plato's Trousers)
    cool. so you are happy with it all now, yes?
    b) 0.1 moles
    c)already right yay
    d)0.05moles
    e)2.5 mol per dm(cubed)
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    (Original post by thepastpaper)

    b) 0.1 moles
    c)already right yay
    d)0.05moles
    e)2.5 mol per dm(cubed)
    Sorry, you haven't got this.

    I think you also have your lettering of the parts of the question wrong. Did you mean to start with a) ?

    The correct answers are:

    a) 0.1 moles/dm3
    b) 0.0025 moles
    c) already correct
    d) 0.00125 moles
    e) 0.0625 moles/dm3

    Do you need me to go through it again with you?
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    (Original post by Plato's Trousers)
    Sorry, you haven't got this.

    I think you also have your lettering of the parts of the question wrong. Did you mean to start with a) ?

    The correct answers are:

    a) 0.1 moles/dm3
    b) 0.0025 moles
    c) already correct
    d) 0.00125 moles
    e) 0.0625 moles/dm3

    Do you need me to go through it again with you?
    arrrrrrgh iv realised my mistake i counted the 4g as moles, so i got everything else as well....... i got the other answers after getting 0.1 moles...... thank you very much much appreciated
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    (Original post by thepastpaper)
    arrrrrrgh iv realised my mistake i counted the 4g as moles, so i got everything else as well....... i got the other answers after getting 0.1 moles...... thank you very much much appreciated
    good stuff. You're welcome.
 
 
 
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