Chemistry 30

On this page Solution Preparation Calculating Dilutions Common Dilutions Assorted Solution Recipes	Other Lab Storage Items Lab Safety Chem 20 Review Assignment Mole Calculations Graphing Tips
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Common Dilutions

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Hydrochloric Acid, HCl
(concentrated hydrochloric acid is 12 M)
CAUTION: Always add the acid to the water!
	Quantity to add to make 1-L solution
0.1 M	8.21 mL
1 M	82.1 mL
3 M	246 mL
6 M	500 mL
Sodium Hydroxide, NaOH
Molar mass of sodium hydroxide = 40.0 g·mol-1
	Quantity to add to make 1-L solution
0.1 M	4.00 g
1 M	40.0 g
2 M	80.0 g
3 M	120 g
6 M	240 g
Sulfuric Acid, H2SO4
CAUTION: Always add the acid to the water!
(concentrated sulfuric acid is 18 M)
	Quantity to add to make 1-L solution
0.1 M	5.6 mL
1 M	55.6 mL
3 M	167 mL
6 M	333 mL

 

Safety Precautions

Dilution of acids

• Always add acid to water (never add water to the acid)

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Solution Preparation

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Although there are several ways to measure solution concentration, molarity (M) is most commonly used. Molarity is measured as the number of moles of solute per liter of solution.

To prepare a 1M solution of a solute you would add 1 mole of the substance to a clean 1-L volumetric flask, partially filled with distilled or deionized water. Allow the solute to dissolve completely. Then add enough water to fill the flask to the mark on the flask.

To prepare a diluted solution, add the required volume of the concentrated solution to a volumetric flask (of the appropriate size), then fill to the mark on the flask

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Calculating Dilutions

 To prepare a dilution, determine the volume and concentration (molarity) of solution that will be required. Use the following equation to determine how much of the concentrated solution will be required:

M1V1= M2V2

where M1 and M2 are the concentrations of the original and diluted solutions and V1 and V2 are the volumes of the original and diluted solutions

Example:

What volume of concentrated hydrochloric acid, 12.0 M, is required to prepare 500 mL of 0.150 M solution by dilution with water?

Solution:

In a dilution question there are 4 variables - M₁, V₁, M₂ and V₂. You will know three of these values and have to calculate the fourth.

M1 = 12.0 M		M2= 0.150 M
V1 = ?		V2 = 500 mL

Set up the formula, and rearrange to solve for the unknown, V₁:

M1V1	=	M2V2
12.0 × V1	=	0.150 × 500 mL
V1	=	0.150 × 500 12.0
V1	=	6.25 mL

To make the required diluted solution, add 6.25 mL of concentrated hydrochloric acid to a 500 mL volumetric flask (or other volume measuring device). Fill to the mark on the flask with water.

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Assorted Solution Recipes

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		Link to Lab Activity
Calcium hydroxide, Ca(OH)2
saturated	see Limewater
Cobalt(II) chloride hexahydrate, CoCl2· 6H2O (acidified)
0.2 M	2.6 g  CoCl2· 6H2O to total solution volume of 100 mL. This produces the pink hydrated form of the equilibrium system. To form the blue chloro-complex side of this equilibrium, add concentrated 12M HCl (as much as 100 mL) until the solution turns blue.	Le Châtelier's Principle Equilibrium demonstrations
Copper(II) nitrate, Cu(NO3)2
0.5M	93.8 g; add distilled water for a total volume of 1 L	Electrochemical Cells
Copper(II) sulfate, CuSO4
1M	160 g; add distilled water for a total volume of 1 L	Electroplating
Copper(II) sulfate, CuSO4 · 5H2O
0.1 M	25.0 g ; add distilled water for a total volume of 1 L	Le Châtelier's Principle
1M	250 g; add distilled water for a total volume of 1 L	Electroplating
Iron(III) chloride, FeCl3
0.1 M	16 g FeCl3 in 50 mL 6M HCl.  add distilled water for a total volume of 1 L	Le Châtelier's Principle
Lead(II) nitrate, Pb(NO3)2
0.5 M	165.6 g; add distilled water for a total volume of 1 L	Electrochemical Cells
Limewater, Ca(OH)2
saturated	1.5 g per liter of water. Stir or shake vigorously for a minute or two. Let stand overnight; filter off the clear solution and store.
	Limewater is often used to test for the presence of carbon dioxide. For example, have a student use a straw and blow into a solution of clear limewater. The solution will turn cloudy. The reactions: Step 1: CO2 + H2O → H2CO3 Step 2: Ca(OH)2 + H2CO3 → CaCO3 + 2H2O
Potassium chloride, KCl
0.1 M	7 g KCl; add distilled water for a total volume of 1 L	Le Châtelier's Principle
Potassium chromate, K2CrO4
0.1 M	19 g K2CrO4, add distilled water for a total volume of 1 L	Le Châtelier's Principle
Potassium dichromate, K2Cr2O7
0.1 M	29 g K2Cr2O7; add distilled water for a total volume of 1 L	Le Châtelier's Principle
Potassium nitrate, KNO3
0.5 M	50.6 g; add distilled water for a total volume of 1 L	Electrochemical Cells
Potassium thiocyanate, KSCN
0.1 M	10 g KSCN; add distilled water for a total volume of 1 L	Le Châtelier's Principle
Zinc nitrate, Zn(NO3)2
0.5 M	94.7 g; add distilled water for a total volume of 1 L	Electrochemical Cells
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