this section helps students how to prepare solution for each laboratory activities. specially life life science fields such as biotechnology, biology, chemistry and medical laboratory

1. University of Gondar
Institute of Biotechnology
Techniques in Biotechnology (Biot.602)
Lecture 2
Solution preparation

2. Objectives:
After completion of this chapter, the student will be able to:
 define different terminologies related to reagent & chemicals.
 know different methods of expressing strength of solution
 Carry out different calculations and prepare different solutions.

3. Definitions of terms:
• Solution: is a homogenous mixture of two or more components that
can be varied in composition within certain limit.
• Every solution consists of two parts, the solvent and solute
• Solvent: is the substance that dissolves the solute. The solvent in most
cases are liquid.
• Liquid solvent are divided in two:-
• Polar solvents, like water, alcohol
• Non-polar solvent like chloroform,benzene,ether,CCl4
• Solute: is the substance that is dissolved in solvent, the solute can be
solids, liquid or gases.
• If a solid or gas is mixed with a liquid, the liquid is considered
as solvent.
• If the solution is a mixture of two liquid, the component present
in large amount is considered as the solvent.

4. Definitions con’t…
• Stock reagent solution
• Is a concentrated reagent solution which is diluted to prepare a
working solution
• Has a longer shelf life and occupies less space in storage than the
working solution
• Working –reagent solution
• Can be diluted from the stock solution or prepared directly from the
reagent chemical following the recommended procedures

5. Types of solution
1.solid solution: - are mixtures of two or more solids and they are
dispersed or mixed randomly throughout one another resulting a
heterogeneous mixture. Eg. Alloys
2.Gaseous solution :-is a homogeneous mixture of two or more
gases
E.g. Air is a solution of O2, N2, H2, CO2 & other gases.
3. Liquid solution: - is a solution where the solvent liquid &
solute are also liquid but it can be solid or gas.

6. • Making a Solution: What You Need to Know
Which is being dissolved
Which is being used to dissolve the solute
The desired concentration
The desired volume

7. Expression of the strength of solution
Expression of the strength of solutions is broadly divided into two
1.Relative Expressions of the concentration
2. Quantitative expression of the concentration.
1. Relative expressions of the concentrations
a. Dilute solution
- Small amount of solute dissolved in large amount of solvent
Example, 00001M NaOH, 1% H2SO4
b. Concentrated solution
Large amount of solute dissolved in a small amount of
solvents Example, 98% H2SO4, 37%

8. Relative expressions of the concentrations
c. Saturated
• It is one in which a given volume of solvent has dissolved all the solute
that it can under a given condition of temperature and pressure.
d. Supper saturated solutions.
A super saturated solution is a solution which holds more solute than it can
hold normally at a given Temperature and pressure.

9. 2. Quantitative expressions of concentration of solution
• The concentration of solutes in a solution can be expressed quantitatively in
physical unties or chemical units.
A. Physical unit:
• Percentages
• Parts per unit
• Density
• Specific gravity
B. Chemical units.
• Mole
• Equivalents
• Molarity
• Normality
• Molality

10. Quantitative expressions…..
1. Percentage
A. Percentage weight by weight % w/w
• This is the number of parts of solute by weight per 100 parts solution
by weight.
Example: - 37gm%w/w HCL means each 100 gm of HCL solution
contain 37gm of HCL and the rest 63 gm solvent (water)
B. Percentage weight by volume (%w/v)
• It is the number of parts of solvents by weight per 100 parts of solution by
volume.
Example:- 98 gm% w/v glucose solution means, 98gm glucose was dissolved in 100 ml
solution.
C. Percentage volume by volume % V/V
• It is the number of parts of solute by volume per 100 parts of solute
Example :- 70% V/V ethanol means,70ml of ethanol was mixed with 30ml of
water.

11. Quantitative expressions…..
• Problem 1, How can the following solutions be prepared?
a) 100 mL of 40% (w/v) polyethylene glycol (PEG)
b) 47 mL of a 7% (w/v) solution of sodium chloride
c) 200 mL of a 95% (v/v) solution of ethanol
• Problem 2, if 30 mL of 70% ethanol is to be prepared from a 95% ethanol stock
solution, how many ml of stock is needed?
• Problem 3, If 8 mL of distilled water are added to 2 mL of 95% ethanol, what is
the concentration of the diluted ethanol solution?

12. Quantitative expressions…..
2. Parts per unit.
• This is to express the number of parts by volume or by weight of solute per
given volume or weight of the solution.
• For example:- If 1ml ethanol (pure) is diluted with 999 ml of water, to
express the number of parts of ethanol, It can be said that ethanol solution
is 1:1000
3. Dilution of solution
• Dilution is the process by which the concentration of or activity of a given solution
is decreased by the addition of solvent.
• A dilution represents the ratio of the concentrated or stock material of the total
final volume of a solution.
• Simple dilution
• A general process of preparing less concentration solutions from a solution of
greater concentration.
• Serial dilution
• It is defined as multiple progressive dilutions ranging from more concentrated
solutions to less concentrated solutions

13. Quantitative expressions…..
Dilution con’t…
Dilution is used to prepare
• Working solution from stock solution
• Measurable concentration of a sample
• Whenever a solution is diluted, its volume is increased and its concentration
decreased, but the total amount of solute remains unchanged.
• The following equation is used to determine the volume (V2) needed to dilute
a given volume of (V1) of solution of known concentration (C1) to the desired
lesser concentration (C2)
C1 x V1 = C2 x V2

14. Quantitative expressions…..
Using Dilutions , molar or normal to Make Complex Solutions
• Solutions often have more than just one solute.
• To make a complex solution with two or more solid solutes, treat each
solute individually
• To make complex solutions from multiple liquid stock solutions by
Treating each dilution individually
Combine them together in one container and
Brings the volume up to your interest.

15. Quantitative expressions…..
• Problem 2, if 30 mL of 70% ethanol is to be prepared from a 95% ethanol
stock solution, how many ml of stock is needed?
• Problem 3, If 8 mL of distilled water are added to 2 mL of 95% ethanol,
what is the concentration of the diluted ethanol solution?
• Problem 4: Suppose you want to make 100ml of a 1X Triton-X solution
using a 100X Triton-X stock solution. How would you do it?
• Problem 5:
• How to prepare 1:100 dilution of acid alcohol solution.
• How to prepare 1:4 acid alcohol solution, phenolchloroform (50:50)
• How to prepare 1:10 serial dilution of soil/water sample for a bacterial
culture.
• Problem 6: Prepare 250ml of 0.1M NaCl and 0.5M Tris-HCl from a
stock solution of 6M NaCl and 1M Tris-HCl.

16. Quantitative expressions…..
B. Concentration of solution in chemical units.
• Commonly used chemical unit to express the quantity of solutes in a
given solution are:-
• Mole , Equivalents, Molarity, Normality and Molality
1. Mole.
• 1 mole of a give substance is its atomic weight or molecular
weight expressed in gram
• For example :-1mole = 6.02 x 1023 particle of substance
1 mole of Na= 23 grams = 6.02 x 1023
1mole of glucose C6H12O6= 180gm
Since, atomic weight of C=12, H=1, O=16
Example:- How can you prepare 2mole of glucose per liter of aqueous
solution?
Solution ?????

17. Quantitative expressions…..
Molar solution (Molarity ) – Moles/Liter; mols/L (M)
• A molar solution is the solutions which contains 1 mole of the
solute per litter of solution. Or a molar solution which contains
one gram molecular weight of a solute per liter of solution.
Simple formula to calculate Morality
Morality (M) = Actual Mass in grams
Mole. Wt x Vol in liter
Example-1: How do you prepare 1 molar solution of NaOH.
Mol wt of NaOH= 40 gm

18. Quantitative expressions…..
Problems: prepare the ff molar solutions
1. Prepare 50ml of 0.5M NaCl solution from 6M solution of
NaCl.
2. How to prepare 100 ml of 0.5M HCl solution.
3. Tris base (25mM), EDTA (10mM), Glucose (50mM).
• Note: See the MW on its package/ container

19. Quantitative expressions…..
Normal solution (Normality) – moles of active ions/L (N)
• Normality is defined as the number of equivalent of solutes that are present in one liter
of solution. If 1 gm equivalent H2SO4 is dissolved in one liter of solution it is called
Normal solution of H2SO4 or 1N H2SO4.
 NB. One equivalent of substance is its equivalent weight expressed in grams.
 Normality = Actual Mass in grams
Equivalent weight x vol. in liter
 Weight to be dissolved = equivalent weight x vol. in L x Normality.
Example-1 what is the normality of KOH. If 5.6gm KOH is dissolved in 1 liter
of solution?
Solution
Actual mass = 5.6gm
Volume = 1 lit
N= Actual Mass in gram
Equ. Wt x vol in lit
= 5.6gm = 0.1NKOH
56 x 1

20. Quantitative expressions…..
Problems:
1. Prepare 100ml of 0.2N NaOH solution.
2. Prepare 100ml of 1N HCl solution