Concentrated and dilute acids and bases

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Dilution of concentrated acid

Calculation
Example: Make 5 mL of a 0.25 M solution from a 1 M solution Using C1V1 = C2V2
To make a fixed amount of a dilute solution from a stock solution, you can use the formula: C1V1 = C2V2 where:

V1 = Volume of stock solution needed to make the new solution
C1 = Concentration of stock solution
V2 = Final volume of new solution
C2 = Final concentration of new solution

Example: Make 5 mL of a 0.25 M solution from a 1 M solution

Formula: C1C1 = C2V2
Plug values in: (C1) * (1 M) = (5 mL) * (0.25 M)
Rearrange: C1 = [(5 mL) * (0.25 M)] / (1 M) C1 = 1.25 mL
Pipette 1.25 ml (graduated pipette) into a 5 ml vol flask, and dilute up to mark with distilld waer.

Commercially available concentrated sulfuric acid is 18.0 M H2SO4.
What volume of concentrated H2SO4 to use in order to make 3.00 L of a 4.0 M stock solution?

You will use the equation (M1)(V1) = (M2)(V2)
The original concentration x initial volume = final concentration x final volume.
In this example, the original concentration is the concentration of the concentrated sulfuric acid which is 18 Molar which is M1 and the final diluted concentration is 4 Molar (M2) with a final volume of 3.00 liters.
To solve for V 1 , multiply 4.0 Molar by 3.00 L and divide by 18.0 M
V1 M1 = M2 M2
V1 = M2.V2/M1
V1 =4.0 M x3.00 L /18.0 M
V1 = 0.67 L =670mls
This means that you need to dilute 670mls of the original stock solution of concentrated acid and add water until it is diluted to 3.00 liters volume.

Dilution pocedure
Standard operating procedures (SOP) required. Approved and practical facility - such as a laboratory with water, and safety stations.
Diluting conc acid gives off much heat when it comes with contact with water and must be diluted using a water bath or ice bath to cool the reaction.
Always add the conc acid o the wafer. Never add the water to the acid.
Only qualified personnei with the latest MSDS info should prepare such dilutions. Students should not be asked to dilute conc acids, but it cab be given to them if it is necessary for their lab work

Table off concentrated acids
Info on how much concentrated acid or base is required to make up 1 liter of 1M dilute acid or base.
A Table showing the no. of mls, percentage, SG, and Molarity of the acids is given.
Quantities used are approximate and acceptable for practical qualitative analysis.
Reagents tend to be hygroscopic or volatile.

Related link :

• Preparation of laboratory reagents

CONCENTRATED ACIDS
Always add acid to water! Observe the lab safety precautions.

Acids	Molarity	Percent	S.G.	To make 1M soln
Acetic acid MW=60.05	17.4M	99%	1.05	58 mls / liter
HCl MW=36.46	11.6M	36%	1.18	Use 86 mls / lliter
Nitric acid MW=63.01	16.4M	69%	1.42	61 mls / liter
H2SO4 MW=98.07	17.6M 36N	95%	1.84	56 mls / liter(1M) 28 mls / liter (1N)
Ammonia soln MW=35.05	14.5M	28%	0.88	69 mls / liter (1M) Use 71 mls / liter (1M)
Hydrobromic acid	9 N	48%	1.49	111 mls /liter (1M)
Hydrofluoric acid MW=20.01	27M	48%	1.29	37 mls /liter (1M)
Hydriodic acid	7M	57%	1.70	143 mls /liter (1M)
Perchloric acid MW=100.46	11.7M 9.5M	70% 61%	1.71 1.66	85.5mls /liter (1M) 106 mls /liter (1M)
Phosphoric acid MW=97.99	45N 15M	88%	1.69	22.5 mls /liter (1N) 68 mls /liter (1M)

DILUTE ACIDS Acetic Acid Dilute 116 mls.of the concentrated acid to 1 litre of water. (2M) Hydrochloric Acid Dilute 172 mls. of the concentrated acid to 1 litre with water.(2M) Nitric Acid Dilute 122mls. of the concentrated acid to 1 liter with water. (2M) Sulphuric Acid Pour 56 mls.of the concentrated acid slowly and with constant stirring into about 500mls. of water, cool, and dilute to 1 litre. (1M) Sulphurous Acid Prepare a saturated solution of SO2 in water. 6-7% by weght. DILUTE BASES Ammonia solution conc. The commercial product, S.G. 0.88 contains about 28% NH3. (15N) Ammonia solution dilute Dilute 335 ml of the commercial solution to 1 liter (5N) Barium hydroxide Shake 70 gms. of crystalised salt in 1 liter of water. Filter or siphon off the liquid , and protect from CO2 of the air 0.2M Calcium hydroxide Shake 2-3 gms. of calcium hydroxide with 1 liter of water. Filter or siphon off liquid, and protest from CO2 of the air. 0.02M Potassium hydroxide Dissolve 112 gms. of KOH pellets in water , and dilute to 1 liter. (2M) Sodium hydroxide Dissolve 200 gm pellets in water and dilute to 1 liter. (5M)

CONCCENTRATED BASES ²

Concentrated bases or alkalis are sold as w/w % solutions and labelled Concentrated Reagent.
Table below give info on three commonly used bases.

Concentrated Reagent	Molarity	Percent	S.G.	To make 1M soln
Ammonium Hydroxide (NH4OH) MW=35.05	14.5M	28% NH3	0.88	69.0 mls / liter
Sodium Hydroxide (NaOH) MW=40	19.4M	50%	1.54	51.5 mls / lliter
Potassium hydroxide (KOH) MW=56.12	11.7M	45%	1.46	85.5 mls / liter

References:

1. A.I. Vogel "Textbook of Inorganic Quantitatiuve Analysis" 3rd. Ed., Longman (1961). (Appendix)
2. J. T. Baker reagent.