molarity = no. of moles of solute / 1 liter .

* one moles of sodium hydroxide = 40 gm of sodium hydroxide.

so we can said ; if want prepare 1 molar NaOH solution then we need 40 gm NaOH dissolve in one liter of water so it became one 1 molar NaOH solution.

Weigh 39.9 gm of NaOH pellets & dissolve them in one liter of water, what you will be having now is 1M NaOH solution.

For calculations, you may wish to employ online tools such as - https://www.graphpad.com/quickcalcs/molarityform.cfm

Your stock solution of Sodium Hydroxide is calculated to be 37.875 M based on a density of 1.515 g/mL, a formula weight of 40 g/mol, and a concentration of 100% w/w.

To make a 1 M solution, slowly add 26.403 mL of your stock solution to 250 mL deionized water. Adjust the final volume of solution to 1000 mL with deionized water.

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Reference : https://www.sigmaaldrich.com/chemistry/stockroom-reagents/learning-center/technical-library/molarity-calculator.html

Dear Ramona,

Be carefull when you do that. Do not add the water on the pellets! Take a part of water and add to the becker. Then, add the pellets carefully. After that, add the rest of the water mixing carefully (always under vent).

I recommend Harvijay's answer

Best Regards

Take the pellets in to a 1lt measuring cylinder and add 1/3 of distilled water and swirl. Once it is completely dissolved, make up the solution upto 1lt mark in the measuring cylinder.

Thank you all!

Hi Ramona,

To make 1 M NaOH solution, you have to dissolve 40.00 g of sodium hydroxide pellets in 250 mL distilled water and then make up the solution to 1 liter.

how much NaoH i have to add in 50ml or 100ml water? if i want to prepare the 1M of NAOH?

You need to take into account the purity of your pellets. e.g., ACS reagent grade pellets are >97% so you could end up with between 0.97M. Also, you have to be careful about the hygroscopicity. The pellets will readily pick up moisture from the atmosphere which will cause you to overestimate the mass of NaOH you dispense.

@John Francis Miller, Does it mean that if the purity of your pellet is 96%; we could end up with 0.96M? IF so, how can we make up to exactly 1M?

To make 1 M NaOH solution, you have to dissolve 40.00 g of sodium hydroxide pellets in 250 mL distilled water and then make up the solution to 1 liter

Ramona Luna

Haruna Kolawole Afolabi - you need to determine the purity of your pellets. To do that, you need to make a solution with a known mass concentration of your pellets and titrate it against an acid of known concentration.

If you just want approx. 1M, then by all means skip this and just dissolve 40g in 1 liter of water as others suggest. But you say you want it "exact", so you need to "standardize" your solution. See this (bottom third of the page is most relevant):

https://www.extension.iastate.edu/wine/preparing-standard-sodium-hydroxide-solution

Why is this so hard to explain? You have to account for the impurities in the pellets if you want an accurate 1M solution. Dissolving 40g of SigmaAldrich NaOH pellets is not the same as dissolving 40g of pure NaOH. Pellets of NaOH have the additional problem of hygroscopicity. You have to standardize your solution.

First weigh 40g NaOH in breaker and dissolve with 400 to 500 mL with purified water. Then allow to cool the solution and volume upto 1000 mL with purified water. Then standardization your Solution.

The question was asked more than 3 years ago

what is your experience now Ramona Luna

If you need to prepare roughly one liter of 1 M NaOH solution, you dissolve the molar mass of NaOH (40.0 g) using distilled water in a beaker, then transfer this solution to a one liter volumetric flask and rinse the beaker with distilled water several times and put it in the volumetric flask, and finally fill the volumetric flask with distilled water to the mark. To know the exact molarity of NaOH, you must standardize it with a primary standard material like potassium hydrogen phthalate (KHP). Now this solution is called secondary standard solution and must be frequently standardized before use, because its molarity changes with time and reduces as it reacts with the atmospheric CO2 when you open it from time to time. Then after that you can use it to find the molarity of other unknown acid solutions or the molar mass of an unknown acid.

You can utilize this web page to accelerate the calculations.

https://www.periodni.com/preparation_of_solutions.php?scq=NaOH

by dissolving 40 g of NaOH (solid) in 1000 ml of distilled water.

Dear Islam Salem Marae,

This is roughly a one molar NaOH. If you need an accurate molarity you must standardize it with a primary standard material like KHP as I mentioned in the previous answer for this question.

Thank u so much, you are egyption aren't you?

Dear Islam Salem Marae,

You are most welcome.

No, I'm Palestinian.

We Know That,

NaOH

Atomic weight of sodium (Na) = 23

Atomic weight of oxygen (O) = 16

Atomic weight of hydrogen (H) = 1

Molecular weight of NaOH = 40

Then,

During the preparation of molar solution the weight to be taken is calculated according to the following method using the formula :-

M x S x V

Where,

M = molar weight

S = strength of required solution

V = volume in liters

Here, Weight = M × S × V

= 40 × 1 × 1

= 40gm

So, we need 40 gm NaOH dissolve in one liter of Distilled water so it became one 1 molar NaOH solution.

Dear Dr. Tapeshwar,

Actually what you prepared is roughly 1 M NaOH solution and it is not accurate. Because as you know NaOH is not primary standard material (hygroscopic). So you must standardize it by KHP (Potassium hydrogen phthalate).

Ibrahim Abdel-Rahman Sir.....Thank you....thank you so much for this kind information ......Best Wishes.....!!!

Dear Dr Tapeshwar,

You are most welcome.

Have a nice weekend.

- Ibrahim A Abdel-Rahman

Tapeshwar Sir please kindly contact me can I assist you in this type of calculation easily

You will need to dissolve 40 g of NaOH in 900 ml of distilled water, and then adjust the volume to 1000 mL. Beware, the reaction is exergonic and will release heat. So if you use a volumetric flask to adjust the volume to 1000 mL, you should do so when the exergonic reaction is over and the temperature of the dilution is room temperature. Otherwise, the glass of the volumetric flask will dilate too much and you will lose volumetric accuracy. For this reason, volumetric flasks should also not be placed in the refrigerator.

Dissolve 40 gm of Sodium Hydroxide in water and volume up to 1000 mL.

Dear Dr J. D. Franco-Navarro,

***Beware, the reaction is exergonic and will release heat.

The correct term for exergonic is exothermic.

Beware, the reaction is exothermic and will release heat.

you have to choose the volume necessary to have a concentration of 1MNaOH

i) Commercial (technical grade) caustic soda (sodium hydroxide) pellets, often of [min.] 96 [wt]% specified purity, typically contain H2O as main impurity. Sodium carbonate is another common impurity found in technical grade caustic soda (usually less than 2 wt%, on delivery).

ii) This standard may help:

ASTM E291 - 18, "Standard Test Methods for Chemical Analysis of Caustic Soda and Caustic Potash (Sodium Hydroxide and Potassium Hydroxide)"; https://www.astm.org/Standards/E291.htm

iii) Concerning to drying sodium hydroxide (pellets), you may want to check the following RG discussion: https://www.researchgate.net/post/Can_granular_sodium_hydroxide_be_dried_in_an_oven

add 40 mg in 1litre of DI water. it is the basic chemistry equation. if you want different concentration or volume you can play with the proportion.

Dear Dr. Nilesh Kumar,

Add 40 g (not 40 mg).....

NaOH is a secondary slandered,it can absorb moisture from air .so we can't prepare it's standard solution by direct weighing of NaOH.

A)first preparation of approximately 1 M NaOH solution:—

Molarity=no of moles÷volume in L

if you want to prepare approx 1M NaOH solution in 250ml volumetric flask then

1000ml—1M—40g of NaOH

250ml. —1M — x g of NaOH

Form above equation

1000ml×1M×X g=250ml×1M×40g

X=[250×1×40]÷[1000×1]

X=10g of NaOH

That is to prepare 250 ml NaOH solution dissolve 10 g NaOH crystals in 250 ml volumetric flask and dilute up to the mark with the distilled water you get approx 1M NaOH solution.

B) Standardization of NaOH solution:—

Take approx 1M NaOH ,25 ml in a conical flask add 2–3 drops of phenolphthalein indicator and titrate with standard oxalic acid solution

Approx

1M NaOH Vs oxalic acid

M1V1. = M2V2

M1×25= 1×V ml acid require for neutri

M1. = Vml÷25 = X M

This M1 is exact molarity of prepared NaOH solution

Dear friend Dr Hicham,

The last step in the calculations of the molarity of NaOH using oxalic acid as a standard solution, you must take into consideration the mole ratio between them. The mole ratio is not one to one,

M1 . V1 ≠ M2 . V2

We must apply:

Fa. Ma. Va = Fb. Mb. Vb

Fa = no. of H+ in the formula of the acid

Fb = no. of OH- in the formula of the base.

M(NaOH). V(NaOH) = 2 M(Oxalic Acid ) V(Oxalic Acid)

Thanks for your notes

The mole ratio is not one to one,

M1 . V1 ≠ M2 . V2

So apply:

Fa. Ma. Va = Fb. Mb. Vb

Dear Dr Baraa,

I think you did not read what is mentioned before by Dr Hicham.

The mole ratio between NaOH and Oxalic acid is not one to one.

Oxalic acid is diprotic acid (C2H2O4).

So Fa =2, while Fb = 1

1. Take weight of 2g sodium hydroxide pellets

2. Transferred in to a volumetric flask of 500 ml.

3. Pour 400 ml of distilled water in to the flask

4. Put cap and swirl to dissolve pellets

5. Add distilled water to make final volume of 500 ml.

6. Rotate the flask several times

7. Take the newly prepared solution in burette

8. Note the initial burette reading

standarization of newly prepared solution

1. Take 10 ml of standard 0.1 N HCL solution in a conical flask.

2. Add one or two drops of phenolphthalein indicator solution in to the flask.

3. Swirl the flask

4. Start titrating

5. Pink colour light

6. Note the final burette reading

Dear Dr Suganth,

To prepare roughly 1 M NaOH solution, you must dissolve 20 g of NaOH in distilled water using 500 ml volumetric flask or 2 g of NaOH in distilled water using 50 ml volumetric flask. Then you must standardize it with a primary standard material like potassium hydrogen phthalate (KHP).

molarity= mole of solute/liter of solution. note our solvent could be distilled and carbon dioxide free water. from basic molarity formula we have obtained mole of solute (NaOH) is equivalent to one. mole=given mass/molar mass from this basic formula, given mass =mole*molar mass. molar mass of NaOH is the sum total of individual elements molar mass (23+16+1)= 40g/mol. from this result we can calculate the given mass of NaOH is equivalent to 40g. Therefore, 40g of NaOH could be dissolved to prepare 1molarity of NaOH.

Dear Dr Milkesa,

What you have mentioned is actually not completely true. What you have prepared is roughly 1 M NaOH solution, because NaOH is not primary standard material. So, you must standardize your solution using a primary standard material such as potassium hydrogen phosphate (KHP).

Dear Dr. Ibrahim Abdel-Rahman,

what quantity of primary standard material is required to standardize the prepared solution? And does the standard material quantity varies with the concentration of the prepared solution?

Dear Dr Anifat Bankole,

This is a good question.

The quantity of the the primary standard material depends on the approximate concentration of the NaOH solution. You must choose an amount of the primary standard material, so that the volume of the the NaOH solution is more than 10 ml and less than the maximum volume of the burette that used in the standardization. Because if the volume is less than 10 ml, the accuracy of the concentration of the NaOH solution will be low (3 significant figures), and also if the volume is more than the maximum volume of the burette, you need to fill the burette again and also the accuracy of the results will be low.

take 40 g 0f solid NaoH and dissolve in 1000 ml

or 20 g in 500 ml

or 10 g in 250 ml @

Dear Dr Nawal,

This will give you roughly 1 M NaOH and not exactly 1.000 M NaOH.

Molarity is number of moles (weight of solute divided by its molecular weight) present in 1 litre of water... molecular weight of NaOH is 40(23+16+1) ...so take 40 gm of NaOH and makeup volume upto 1 litre by adding water....

Dear Dr Himanshu,

What you have mentioned is only correct if the material is primary standard material, but as you know NaOH is not a primary standard material. So, you must standardize the prepared NaOH solution using a primary standard material like potassium hydrogen phthalate (KHP).

Vadim S. Gorshkov

Vadim S. Gorshkov

https://www.researchgate.net/post/How_to_make_10N_of_NaCl

... and spot the obvious problem... (never mind using normalities rather than molarities).And see what got 11 recommendations...

Vadim S. Gorshkov

@vadim S.

You can standardize the NaOH solution using a standard material like potassium hydrogen phthalate (KHP) instead of buying it and paying too much money.

Best Regards.

- Ibrahim A Abdel-Rahman

To prepare a 1M NaOH solution, dissolve 40.00 g of sodium hydroxide pellets in 250 mL of distilled water and then make up the solution to 1 liter

Dear Abdelhak,

This is roughly one molar NaOH solution, because NaOH is not primary standard material.