topic 17894

# Sodium Hydroxide: How to make to 0.5 M strength

A discussion started in 2002 but continuing through 2017

2002Q. Hello Folks,

Can anybody help me to make a 0.5 M NaOH solution, I forgot that formula?

Thanks,

Reynaldo Arroyo- Valencia, California, U.S.A.

2002
A. NaOH has a valence of 1, so molar and Normal are the same. One mole of NaOH in one Liter of pure water = 1 N. Since you want 0.5, use 1/2 mole (20.0 grams) of NaOH. If this is for a titration, you will need to standardize it. By the time you make it up, filter it (if required), cool it and then standardize it, you will find that it is cheaper to buy the premade solution from VWR-SP or Fisher or ?. James Watts- Navarre, Florida 2002 A. Dissolve 20 g NaOH to a total volume of 1 L in water. - Tallahassee, Florida |

2002
A. Dear Mr Arroyo, One mole of NaOH weighs 23(Na)+16(O)+1(H)=40 g Kind regards, - Eindhoven, The Netherlands 2002 A. M means Gram Molecular Weight, so 0.5 M means half the gram molecular weight of the chemical. In the case of NaOH the mole. wt. is Na=23, O = 16, H =1, so NaOH = 40. Half of that is 20, so 0.5 M NaOH is the same as 20 g/l. I trust you now remember your basic chemistry. R&D practical scientist Chesham, Bucks, UK |

September 17, 2013

Q. Please help me with my research: How are we going to prepare a half molar NaOH?

Angel de Silva- Davao City, Philippines

September 23, 2013

A. Hi Angel. A "half molar" solution is the same as "0.5 M", so this was already answered 4 times. If you are still confused, please explain in what way these answers are proving unsatisfactory. Thanks.

Regards,

Ted Mooney, P.E.

finishing.com

Pine Beach, New Jersey

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March 26, 2015

A. To make 0.5 M of NaOH, measure 20 g of sodium hydroxide and dissolve it in 1000 ml of water; we have used 20 g because the RMM [relative molar mass] of NaOH is 40 and we are making 0.5 M solution.

cyprian nthuli- mombasa , kenya

September 29, 2015

Q. How many grams NaOH are needed to prepare 500 ml of 0.5 M NaOH

jelo pabular- Cebu city, Philippines

I think these students are just pulling our leg now, rather than not knowing how to divide by two. Thank god I didn't go into teaching :-)

Regards,

Ted Mooney, P.E. RET

finishing.com

Pine Beach, New Jersey

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December 20, 2015

Q. Dear Friends,

I have a Query regarding the Sodium hydroxide solution preparation. I prepared the sodium hydroxide solution with respect to 15 gram per liter and poured into a glass bottle, after 2 days I titrated it to find out the concentration of NaOH and surprisingly found that NaOH conc. reduces to 10 g/l and even I found aluminum as 4 g/l, so can somebody explain me how this aluminium introduced into this solution?

- Abu dhabi, UAE

A. Hi Aijazullah. It's obviously either experimental error or a jar which contained reactable aluminum. Good luck.

Regards,

finishing.com

Pine Beach, New Jersey

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April 20, 2016

Q. How to make 20% sodium hydroxide solution from a 1 Normal solution?

Tammy Lee- Birmingham, Alabama, USA

April 2016

A. Hi Tammy. As you can see from the 5 explanations above, your 1N solution is 40 g / 1000 g or 4% by weight. You could heat it and evaporate the water until it was 20% NaOH by weight, but I doubt that evaporating the water from a dilute caustic solution to make a more concentrated and dangerous one would be approved by your university these days though. Good luck.

Regards,

finishing.com

Pine Beach, New Jersey

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April 3, 2017

Q. How do I prepare 0.4 mol/l of NaOH? Someone help please.

UMAHI O [last name deleted for privacy by Editor]diagnostic center - Nigeria

April 2017

A. Hi Umahi. The calculation for this has been explained 6 times on this page now. Please take the time to tell us what it is that you are not understanding. I would be worried about the sufficiency of my haz-mat training if I were you because this is pretty basic stuff you should know before you work with hazardous chemicals. Good luck.

Regards,

finishing.com

Pine Beach, New Jersey

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A. The best way is to make a 50% w/w solution of NaOH in DI water, allow it to cool, let any solids settle out (Na2CO3) and then weigh out 8.0 g of this prep into a volumetric flask. Make up to the mark with DI, with lots of swirling, let cool, then make up to the mark again.

For maximum accuracy, a standardization vs. KH pthalate would be advisable. Check "Standard Methods" for this procedure.

This is really kind of basic Chem 101 stuff, if I may say.

Dave Wichern

Consultant - The Bronx, New York

April 4, 2017

Q. I have a 5% solution of Sodium Hydroxide w/v.

I would like a 1.5% solution of Sodium hydroxide.

How do I solve this?

- Tualatin, Oregon, USA

April 2017

A. Hi Stan. I guess you're saying you have a solution with 50 grams of NaOH for every 1000 mls? And you would like to dilute it to the point where you have only 15 grams of NaOH for every 1000 mls?

So for every 15 mls of solution of 5% solution you wish to dilute, add 35 mls of water to end up with 50 mls of 1.5% solution.

Regards,

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Pine Beach, New Jersey

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