Weight/Volume Percent
Weight/Volume % = grams of solute x 100
volume of solution
A weight per volume percent concentration is the weight of the solute in grams per 100 mL of solution. It can be abbreviated as w/v.
A student adds 20.0 grams of NaCl to volumetric flask and fills it to the 100mL mark. What is the weight per volume (w/v) percent concentration of the solution?
Weight % = grams of solute x 100 volume of solution
Weight % = 20.0 grams x 100 100mL of solution
Weight % = 20% NaCl solution
How many grams of NaCl would be needed to prepare 500 ml of a 5% solution of NaCl?
Grams of solute = Volume of solution x Weight %
Grams of solute = 500mL x 5%
Grams of solute = 500mL x 5g/100mL
Grams of solute = 25 g of NaCl
Volume/Volume Percent
volume % = volume of solute x 100 volume of solution
Volume % = mL of solute x 100 100 mL of solution
In a percent by volume expression, both the amount of solute and the total solution are expressed in volume units. It can be abbreviated as v/v.
A student adds 20.0 ml of ethanol to a volumetric flask and fills it to the 1L mark. What is the percent volume (v/v) concentration of the solution?
Volume % = volume of solute x 100 volume of solutionVolume % = 20.0 mL of solute x 100
1000mL of solutionVolume % = 2%
How many milliliters of ethanol would you need to make 10.0 mL of a 10% by volume solution of ethanol in water?
volume of solute = Volume of solution x Volume /volume %
volume of solute = 10.0 ml x 10%
volume of solute = 1.0 ml ethanol
Weight Percent
Weight % = weight of solute weight of solution x
100
In a Weight (mass) Percent the numerator is the mass of solute and the denominator is mass of total solution.
What is the weight percent of glucose in a solution made by dissolving 4.6 g of glucose in 145.2 g of water?
Determine total weight of solution: 4.6 g glucose
+ 145.2 g water 149.8 g solution
Calculate Weight % glucose = 4.6 g glucose x 100 = 3.1% glucose149.8 g solution
20. What is the weight percent of sucrose in a solution made by dissolving 29.89 g of sucrose in 1000 g of water?
29.89 + 1000 = 1029.98 solution
29.89/1029.98 x 100 =
2.90 %
How much NaCl would you need to prepare 400 g of a 2.50% solution of sodium chloride?
Grams of solute = Gram of solution x Weight/Weight %
Grams of solute = 400 g x 2.50 %
Grams of solute = 10.0 g salt
1. A chemist adds 78.5 grams of MgCl2 to volumetric flask and fills it to the 1L line. What is the weigh per volume percent of the solution?
Weight % = grams of solute x 100 volume of solution
Weight % = 78.5 g x 100 1000mL of solution
7.85 %
2. How many grams of NaCl would be needed to prepare 600 ml of a 34% solution?
Grams of solute = Volume of solution x W/V %
Grams of solute = 600ml x 34 %
204 grams NaCl
3. How many grams of KCl would be needed to prepare .4 L of a 25% solution?
400 mL x 25%
100 grams KCl
4. How many grams would be needed to prepare an 11% solution of sucrose in 350 ml?
350 x 11%
38.5 grams
5. Find amount of milligrams present in: 75 mL CaCo3 solution with a concentration of 3 mg/ml.
75ml x 3mg/ml
225mg
6. A student adds 20 ml of methanol to 400ml flask and fills it to the mark. What is the percent per volume (v/v) concentration of the solution?
20ml/400ml x 100
5%
7. 37ml of a substance is put into a 500 ml flask filling it. What is the v/v concentration of the solution?
37 ml/500ml x 100
7.4%
8. 50 ml of a substance is added into a 1.25 L flask, filling it. What is the percent volume concentration of the solution?
50ml/1250 x 100
4%
9. How many milliliters of ethanol would you need to make 100 mL of a 23% by volume solution?
100ml x 23ml/100ml
23 ml ethanol
10. What is the weight percent of NaCl in a solution made by dissolving 480 g of NaCl in 1000 g of water?
Weight % = weight of solute weight of solution x
100
480/1480 x 100
32.43%