Sodium hydroxide / volume / concentration question

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Mickelking123
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Guys, im really struggling with this question. Need help. Please help me.

A student needs 50 cm3 of 0.1 mol dm3 sodium hydroxide for an experiment. They are given a bottle of sodium hydroxide with a concentration of 1 mol dm3. Calculate the volume of the sodium hydroxide needed from the bottle and the volume of water to be added so as to get the correct volume and concentration for their experiment.
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tony_dolby
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I'll have a go, but I might be wrong - it's a long time since I did dilutions! As with all chemistry problems, it's a good idea to work out how many moles you have (or need). Moles NaOH needed = conc. x vol. = 0.1 x 50/1000 = 0.005 moles

The NaOH solution provided is 1mol/dm3 . How much of this solution do we need to provide 0.005 moles? Vol. = mol/conc = 0.005/1 = 0.005 dm3 = 5cm3

We now have our 0.005 moles of NaOH. We want a concentration of 0.1 mol/dm3 How much volume do we need for this?
Vol. = mol/conc = 0.005/ 0.1 = 50cm3

The total volume of our solution must be 50cm3 , but don't forget that we already have 5cm3 of NaOH in our volumetric flask.

We must now add 45cm3 of water to make the required volume.
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Mickelking123
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(Original post by tony_dolby)
I'll have a go, but I might be wrong - it's a long time since I did dilutions! As with all chemistry problems, it's a good idea to work out how many moles you have (or need). Moles NaOH needed = conc. x vol. = 0.1 x 50/1000 = 0.005 moles

The NaOH solution provided is 1mol/dm3 . How much of this solution do we need to provide 0.005 moles? Vol. = mol/conc = 0.005/1 = 0.005 dm3 = 5cm3

We now have our 0.005 moles of NaOH. We want a concentration of 0.1 mol/dm3 How much volume do we need for this?
Vol. = mol/conc = 0.005/ 0.1 = 50cm3

The total volume of our solution must be 50cm3 , but don't forget that we already have 5cm3 of NaOH in our volumetric flask.

We must now add 45cm3 of water to make the required volume.
Yeah Tony it's correct. Thanx alot. You're the greatest. Really appreciate it.
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