techniques in chemistry lab

1. Preparation of solution
TECHNIQUES IN CHEMISTRY LABORATORY
SKL 1023
DR.LEE TIEN TIEN
GROUP B

2. NAME MATRIX NO
NORSYAFIQAH BT ROSLI E20121004959
ATHIFAH BT ISMAIL E20121003644
AZURA BT CHE AZMI E20121004984
FATEN NADIA BT MASRI E20121004999
SITI SHAHRIFFAH NORAINY
BT SAHRANI
E20121004927
ADRINA BT KASIM E20121004962

3. What should we learn?
 Preparing solution of target
concentration
 Correct apparatus for preparing
solution
 Safety precautions in preparing of
solution
 Proper method in transferring and

4. Introduction to preparing solution
 Many experiment involving chemicals
call for their use in solution from. That
is, two or more substances are mixed
together in known quantities.
 This may involve weighing a precise
amount of dry material or measuring a
precise amount of liquid.
 Preparing solutions accurately will
improve an experiment’s safety and
chances for success.

5. Let’s understand the terms !!
solute
• Substance which dissolves in
a solution
solvent
• Substance which dissolves
another to form a solution
• Example: water is the solvent

6. Continue….
solution
•Mixture of two or more pure substances
mole
• The amount of pure substance containing
the same number of chemical units
• 1mole is 6.02 X 1023 molecules of that
substance

7. Safety precaution in preparing
solution
Check the label on all chemical
bottles twice before removing any
of the contents
Make sure all chemicals are
clearly and currently label with the
correct name and concentration

8. Continue…
Never return any unused
chemicals to their original
container
Treat any chemical as if it is
HAZARDOUS

9. Measurements and Significant
Digits

10.  One of the most important
requirements of a good scientist is the
ability to properly record
measurements to the correct number
of significant digits and with the
correct units. Examples of the types of
volumetric glassware and instruments
encountered in the laboratory are
given below with directions on how to
correctly record measurements.

11. Apparatus are Commonly used in
Preparation of Solution

12. Beaker
Not designed
to accurately
measure
volumes of
liquids.
Designed to
hold a
particular
amount of
liquid
come in
various sizes
with different
calibrations
These
measurements
have a ±5%
error and are
therefore
approximations.

13. An examination of the 100-mL
beaker shown reveals
calibration lines every 10 mL
between 20 and 80 mL. These
measurements have a ±5%
error and are therefore
approximations
.
The 250-mL beaker has
calibration lines every 25 mL
between 25 and 200 mL. The
error again is ±5%. The amount of
liquid in the beaker is therefore
125 mL ±5%.

14. Erlenmeyer
flask
Not
designed to
accurately
measure
volumes of
liquids.
useful for
stirring
solutions
during
titrations and
synthetic work.
most common
sizes of
erlenmeyer
flasks probably
are 250 ml and
500 ml.
also designed
to hold a
particular
amount of
liquid

15. Erlenmeyer flasks come in various sizes.
An examination of the 250-mL flask shown
gives calibration lines every 25 mL
between 50 and 200 mL. These
measurements have a ±5% error and are
therefore approximations.
The 500-mL Erlenmeyer flask has
calibration lines every 50 mL between 200
and 500 mL. The error again is ±5%. The
amount of liquid in the flask is therefore
500 mL ±5%.

16. Graduated
cylinder
calibrated to contain
(TC) or to deliver
(TD) a precise
amount of liquid
more accurate and
precise than flasks
and beakers for this
function
Tolerances vary with
the size of the
graduated cylinder.
Tolerances may or
may not be given at
the top of the
cylinder neck. If not
shown, use one half
interval division.

17. The 50-mL graduated cylinder shown
has 1-mL divisions and a tolerance of
±0.50 mL and is calibrated to contain
the measured volume.
A graduated cylinder marked TC will
hold the volume measured but will
not deliver that volume to the
container when transferred.
Some of the liquid will remain behind
in the graduated cylinder.
If an exact amount is to be
transferred, the graduated cylinder
should be marked. TD.

18. MEASUREMENTS:
Water and aqueous solutions will form a
concave meniscus when placed in a
graduated cylinder as the water molecules are
more strongly attracted to the glass than each
other. The bottom of the curved surface is
read at eye level and the volume
measurement is read to the proper number of
significant digits.

19. Determine the smallest division marked on the
graduated cylinder: (1) find two adjacent
markings that have a numeric label, (2) subtract
and divide by the number of divisions between
the numeric labels.
Numbers are scaled to increase from bottom to
top of the graduated cylinder. Using the scale
markings, determine the value of the certain
digits.
Estimate the distance the meniscus lies
between markings as a decimal fraction.
Multiply the fraction times the division increment
from Step 1. Add this to the certain digits to
provide the uncertainty in the measurement.
Follow this step to make volume measurement with proper
number of significant figure

20. EXAMPLE 1
Step 1. The labeled scale markings are 8
mL and 6 mL. There are 10 divisions
between the numeric labels. [(8-6)/10] mL
= 0.2 mL is the increment value.
Step 2. The first certain digit is 6 mL since
the meniscus is below 8 mL. There are
three smaller scale divisions below the
meniscus: 3 x 0.2 mL/division = 0.6
mL The known digits are (6 + 0.6 ) mL =
6.6 mL
Step 3. The meniscus lies 0.1 of the
distance between the markings: 0.1 x 0.2
mL = 0.02 mL The volume should be
recorded as (6.6 + 0.02) mL = 6.62 mL

21. Burette
• A burette, is a uniform-bore glass tube
with fine gradations and a stopcock at
the bottom, used especially in
laboratory procedures for accurate
fluid dispensing and measurement.
• Like graduated cylinders, burettes
come in various volume sizes.
• Care must be taken when filling the
burette that the tip contains no air
bubbles.
• The burette is commonly used in
titrations to measure precisely how
much liquid is used.

22. measurement
Water and aqueous
solutions will form a
concave meniscus when
placed in a burette similar
to a graduated cylinder
The bottom of
the curved
surface is
read at eye
level and the
volume
measurement
is read to the
proper
number of
significant
digits.
Use the steps given for
graduated cylinders to make
the volume measurement
with the proper number of
significant digits
Note that,
unlike the
graduated
cylinder, the
numbers are
scaled to
increase
from top to
bottom.

23. EXAMPLE 1
Step 1. The labeled scale markings
are 14 mL and 15 mL. There are 10
divisions between the numeric
labels. [(15-14)/10] mL = 0.1 ml is the
increment value.
Step 2. The first
certain digit is 14 mL
since the meniscus is
below 14 mL. There
are zero smaller scale
division above the
meniscus: 0 x 0.1
mL/division = 0.0 mL
The known digits are
(14 + 0.0 ) mL = 14.0 mL
Step 3. The meniscus
lies 0.5 of the distance
between the markings:
0.5 x 0.1 mL = 0.05 mL
The volume should be
recorded as (14.0 + 0.05)
mL = 14.05 mL

24. A pipette is a type of chemical dropper used in
laboratory experiments to measure and
transport fixed volumes of chemicals

26. Volumetric flasks are calibrated to
contain a precise volume of solution and
are, therefore, often used to prepare
solutions needed for quantitative
analysis.
The neck of the flask has a calibration
mark to indicate the fill level for the
volume of solution needed.
The bottom of the meniscus is lined up
with this mark to insure accuracy.

27. The flask can also be used for
dissolving substances in specific
liquids.
This method is carried out if someone
wants to find out what solutions can
be produced if particular liquids and
substances are mixed together.
This flask is also used when two
different liquids are chosen to be
mixed together.

28. MEASUREMENTS: Note the
volume given on the
volumetric flask. Tolerances
are usually within a few
hundredths of a mL. When
filled to the calibration mark,
the flask shown would
contain 100.00 mL
(0.10000 L) of solution.

29. Technique

30. An electronic balance is a device
used to find accurate
measurements of weight. It is
used very commonly in
laboratories for weighing
chemicals to ensure a precise
measurement of those chemicals
for use in various experiments.

31. PREPARATION OF SOLUTION
FROM SOLID

32. PREPARATION OF SOLUTION
FROM SOLID
 This is how to make a chemical
solution using a solid dissolved in a
liquid, such as water or alcohol.
 If you don't need to be very
accurate, you can use a beaker or
Erlenmeyer flask to prepare a
solution.
 More often, you'll use a volumetric
flask to prepare a solution so that
you'll have a known concentration of
solute in solvent.

33. STEPS OF PREPARATION OF
SOLUTION FROM SOLID
STEP 1
• Weight out the solid that is your solute .
STEP 2
• Fill the volumetric flask about halfway with distilled
water or deionized water (aqueous solutions) or other
solvent.
• Volumetric flasks are used to accurately prepare
solutions for chemistry.
STEP 3
• Transfer the solid into the small beaker or volumetric
flask.
• More easier to dissolve the solid if transfer to the small
beaker than the volumetric flask.
• Use the funnel to transfer the solid or the solution into
the volumetric flask.

34. STEP 4
• Rinse the weighing dish and the funnel with the
water to make certain all of the solute is transferred
into the flask.
STEP 5
• Stir or swirl the solution until the solute is dissolved.
You may need to add more water (solvent) or apply
heat to dissolve the solid.
STEP 6
• Fill the volumetric flask to the mark with distilled or
deionized water.
• Closed tightly with stopper and invert several time to
get homogeneous solution.

35. HOW TO GET PRECISE
AMOUNT OF SOLUTION
 Many experiments involving chemicals substances
for their use in solution form.
 That is, two or more substances are mixed together
in known quantities.
 This may involve weighing a precise amount of dry
material or measuring a precise amount of liquid.
 Preparing solutions accurately will improve an
experiment's safety and chances for success.

36. Solution 1: Using percentage
by weight (w/v)
 Formula :
 The formula for weight percent (w/v) is:
[Mass of solute (g) / Volume of solution (mL)]x
100

37.  Example
A 10% sodium chloride (NaCl) solution has
10g of NaCl dissolved in 100 mL of solution.
STEPS :
Weight 10g of NaCl.
Pour it into a graduated cylinder or volumetric
flask containing about 80mL of water.
Once the NaCl has dissolved completely (swirl
the flask gently if necessary), add water to bring
the volume up to the final 100 mL.

38. Solution 2: Molar Solutions
 Molar solutions are the most useful in
chemical reaction calculations because
they directly relate the moles of solute to
the volume of solution.
 Formula: The formula for molarity (M) is:
or

39. Example :
How much sodium chloride is needed to
make 1 liter of an aqueous 1 M solution?
• First, calculate the molecular weight
(MW) of sodium chloride.STEP
1
• Checking the Periodic Table of
Elements, find that the atomic weight
of sodium (Na) is 23 and the atomic
weight of chlorine (Cl) is 35.5.
STEP
2

40.  Therefore, the molecular weight of
sodium chloride (NaCl) is:
Na (23) + Cl (35.5) = 58.5
grams/mole

41. • To make a 1M aqueous solution of
NaCl, dissolve 58.5 grams of NaCl
in some distilled deionized waterSTEP 3
• Then add more water to the flask
until it totals 1 liter.
STEP 4

42.  To make molar NaCl solutions of other
concentrations dilute the mass of salt to
1000ml or 1 liter of solution as follows:
 0.1M NaCl solution requires:
0.1 x 58.44 g of NaCl = 5.844g
 0.5M NaCl solution requires:
0.5 x 58.44 g of NaCl = 29.22g
 2M NaCl solution requires:
2.0 x 58.44 g of NaCl = 116.88g

43. Preparation of Solution
Through Dilution Method

44. Concentration =
What we need to know?
 Concentration of Solution:
 Expression of Concentration:
The amount of solute that dissolved in a certain
amount of solution.

45. Molarity =
•Unit of concentration: Molarity (M)
 Formula to calculating dilution:
M1V1 = M2V2 or C1V1 = C2V2
where:
M1 = Molarity before dilution
C1 = Concentration before dilution
M2 = Molarity after dilution
C2 = Concentration after dilution
V1 = Volume before dilution
V2 = Volume after dilution

46. Steps that should be taken in
preparation of solution :
STEP 3
Calculate volume of starting solution required using equation M1V1 = M2V2 .
(Note: V1 must be in the same units as V2).
STEP 2
Determine the molarity of starting.
STEP 1
Decide the volume and molarity of the final solution should be.
(Volume can be expressed in liters or milliliters).

47. Example:
Prepare 100mL of 1.0M hydrochloric
acid, HCl from concentrated (1.21M)
hydrochloric acid, HCl.
Solution:
M1V1 = M2V2
(12.1M)(V1) = (1.0M)(100mL)
V1 = 8.26 mL conc. HCl
Thus, we need 8.26mL from stock of
1.21M HCl to prepared 100mL of a 1.0M
of HCl.

48. How to prepared dilution from
the laboratory ? Take out the 8.26mL of
1.21M HCl from the
stock. (By using a
pipette)
Transfer to the
100mL volumetric
flask.
Fill in the volumetric flask with
distilled water until it nearly to
calibration mark.
( Used a dropper to make the
dilution exactly to the calibration
mark)
Closed tightly with stopper and
invert several time to get
homogeneous solution.

49. Thank you…
For listening and your
attention…