Making solutions of differing mass/volume concentrations

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Making Solutions in the Biotech Laboratory
Lab A: Making solutions of differing mass/volume concentrations
Solutions are prepared with a certain mass of solute in a certain volume of solvent, similar to glucose solutions
made in the previous activity. Any metric mass in any metric volume is possible, but the most common units of
mass/ volume concentrations are as follows: g/mL, g/L, mg/mL, µg/mL, µg/µL, ng/L, ng/µL.
Although concentrations can be reported in any mass/volume units, these 7 mass/volume units are the most
common in biotech applications. the prefix “nano-“ means one billionth. A nanogram is equal to 0.001µg, and
there is 1000ng in 1 µg.
Mass/Volume Concentration Equation
Concentration desired
x total volume desired = mass of solute in the total volume desired
In this activity you will be making solutions with differing mass / volume concentrations. Remember to check
that your units match while doing your calculations! Be sure to show all of your calculations in the “data”
section of your lab notebook! When you are finished with your solutions, bring them up to the front of the
classroom and compare them with your teacher’s “key” solutions.
Solution #A1: Make 20mL of a .25 g/mL NaCl solution
Solution #A2: Make a .003g/mL and make 100mL of it.
Lab B: Making solutions of differing % mass / volume concentrations
A lab technician must be able to make any solution at any concentration or volume. Most commonly, solutions
are made with concentrations reported in one of these three measurements: Mass / Volume, % (in mass/volume)
and Molarity.
Preparation of % mass/volume solutions is presented in this activity. Since you will be required to make a
variety of % mass/volume solutions at several different concentration and volumes, us the equation shown
below to calculate the mass of each solute needed for a solution at some volumes.
% Mass/Volume Concentration Equation
Step #1: Convert the % to a decimal (% value = decimal value of g/mL)
Step #2: Decimal g/mL of the % Concentration x volume (mL) = grams of solute to be measured
In this activity you will be measuring out sugar to prepare differing % concentration solutions. Be sure to show
all of your calculations in the “data” section of your lab notebook! When you are finished with your solutions,
bring them up to the front of the classroom and compare them with your teacher’s “key” solutions.
Solution #B1: Make 15mL of a 12% sugar solution
Solution #B2: Make 5mL of a 5% sugar solution
Lab C: Making solutions with differing Molarity Concentrations
The concentration of many solutions is reported as moles/liter (mol/L or M). This concentration measurement
is called molarity. Molarity is sometimes a challenging concept to understand. However, with your recently
acquired solution preparation skills, you will see that making molar solutions requires only one extra
calculation. To understand how to make a solution of a given molarity, you must know what a “mole” is. In
biotech, the unit “1 mole” is the mass, in grams, equal to the molecular weight of the substance. The equation
below will guide you calculating the mass of solute in molar concentration solutions.
Molarity Concentration Equation
Volume wanted x molarity desired x molecular weight of solute = grams of solute to be dissolved
(L)
(mol / L)
(g/mol)
In this activity you will be making differing molar solutions with NaCl. Be sure to show all of your calculations
in the “data” section of your lab notebook! When you are finished with your solutions, bring them up to the
front of the classroom and compare them with your teacher’s “key” solutions.
Solution # C1: Make 50mL of a 1.5M NaCl solution
Solution # C2: Make 25mL of a .5M NaCl solution
Lab D: Making Dilutions of Concentrated Solutions
Making dilutions of concentration solutions is a common practice in a biotechnology lab. A concentration
solution is generally called a “stock solution”, and the diluted solution is called the “working solution”.
Preparing a concentrated stock solution saves a lot of time and is easier to store than large volumes of diluted
working solutions. Making a working solution simply requires diluting some volume of stock solution to the
concentration needed. The equation below should be used to calculate the amount of the concentrated stock
solution to use for the dilution.
Diluting Concentrated Solutions Equation
C1 V1=C2 V2
Where C1= the concentration of the stock solution (the more concentrated one)
V1= the volume to use of the stock solution in the diluted sample
C2= the desired concentration of the diluted sample
V2= the desired volume of the diluted sample
In this activity you will be diluting a 10x solution down to lower concentration solutions. Be sure to show all of
your calculations in the “data” section of your lab notebook! When you are finished with your solutions, bring
them up to the front of the classroom and compare them with your teacher’s “key” solutions.
Solution #D1: Use your 10M Stock solution to create 20mL of a 5M stock solution.
Solution #D2: Use your newly created 5M solution to make 30mL of a 2M solution.
Conclusion Questions:
1. Which of the above sections gave you the most trouble (A, B, C, or D) and why do you think it gave you
trouble?
2. Convert the values indicated below and specify the appropriate instrument with which the final
measurements should be made.
1)
2)
3)
0.42 g = __________ µg
90.22 µg = __________ g
0.0285 mL= __________ µL
___________________
_____________________
____________________
4)
999µL= __________ mL
5)
80.41 mL = __________ µL
6)
70.503 mg = __________ g
___________________
______________________
______________________
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