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    I found a question in my revision guide and I really didn't understand how to get the answer. I've tried working backwards and looking online, but it's no good -.-
    Can someone help?! If you can, write the working out please!

    The question is:
    explain 5cm^3 of a soltion has a concentration of 1 mol/dm^3. How much water should be added to the solution in order to make it have a concentration of 0.1mol/dm^3?

    Please help! And thanks in advance!
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    1. Convert the 5cm³ into dm³.
    There are 1000cm³ in 1dm³
    5cm³ ÷ 1000cm³/dm³ = 0.005dm³.

    2. You find the amount of the substance for which the concentration will change
    intiial concentration (mol/dm³) = amount (mol) ÷ initial volume (dm³)
    amount = concentration ×volume
    amount = 1mol/dm³ × 0.005dm³
    amount = 0.005mol

    3. No more of the substance will be added, but more water will be added, so the amount will stay the same.
    final concentration (mol/dm³) = amount (mol) ÷ final volume (dm³)
    volume = amount ÷ concentration
    volume = 0.005mol ÷ 0.1mol/dm³
    volume = 0.05dm³

    4. Remember you aren't working out 'final volume', you are working out 'change in volume'
    change in volume = final volume - initial volume
    change in volume = 0.05dm³ - 0.005dm³
    change in volume = 0.045dm³

    5. You can convert the 0.045dm³ to cm³ (I don't know if the question needs you to do this)
    There are 1000cm³ in 1dm³
    0.045dm³ × 1000cm³/dm³ = 45dm³

    You would need to add 45cm³ of water
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    (Original post by emperorCode)
    1. Convert the 5cm³ into dm³.
    There are 1000cm³ in 1dm³
    5cm³ ÷ 1000cm³/dm³ = 0.005dm³.

    2. You find the amount of the substance for which the concentration will change
    intiial concentration (mol/dm³) = amount (mol) ÷ initial volume (dm³)
    amount = concentration ×volume
    amount = 1mol/dm³ × 0.005dm³
    amount = 0.005mol

    3. No more of the substance will be added, but more water will be added, so the amount will stay the same.
    final concentration (mol/dm³) = amount (mol) ÷ final volume (dm³)
    volume = amount ÷ concentration
    volume = 0.005mol ÷ 0.1mol/dm³
    volume = 0.05dm³

    4. Remember you aren't working out 'final volume', you are working out 'change in volume'
    change in volume = final volume - initial volume
    change in volume = 0.05dm³ - 0.005dm³
    change in volume = 0.045dm³

    5. You can convert the 0.045dm³ to cm³ (I don't know if the question needs you to do this)
    There are 1000cm³ in 1dm³
    0.045dm³ × 1000cm³/dm³ = 45dm³

    You would need to add 45cm³ of water
    Thanks for the help! It's so much more clear now!
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    (Original post by DangIt)
    Thanks for the help! It's so much more clear now!
    No problem... helped me revise concentrations for myself - it's a win for both of us.
    (Thanks for the rep, means a lot to me and for the practise)
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    (Original post by emperorCode)
    No problem... helped me revise concentrations for myself - it's a win for both of us.
    (Thanks for the rep, means a lot to me and for the practise)
    XD totally fine
 
 
 
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