chemistry : Preparation of solution

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 handling solution

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 !!

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7. Safety precaution in preparing solution

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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. 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%.

13. 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%.

14. 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.

15. 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. 

16. Follow this step to make volume measurement with proper number of significant figure

17. 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

18. EXAMPLE 1

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

20. Volumetric Flasks

21. 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.

22. Technique

23. 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 .

24. PREPARATION OF SOLUTION FROM SOLID

25. 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.

26. STEPS OF PREPARATION OF SOLUTION FROM SOLID

27. 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.

28. 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

29. Example A 10% sodium chloride ( NaCl ) solution has 10g of NaCl dissolved in 100 mL of solution. STEPS :

30. 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

31. Example : How much sodium chloride is needed to make 1 liter of an aqueous 1 M solution?

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

33. 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

34. Preparation of Solution Through Dilution Method

35. Concentration = What we need to know? Concentration of S olution : Expression of Concentration : The amount of solute that dissolved in a certain amount of solution .

36. Molarity = Unit of concentration: Molarity (M) Formula to calculating dilution: M 1 V 1 = M 2 V 2 or C 1 V 1 = C 2 V 2 where : M 1 = Molarity before dilution C 1 = Concentration before dilution M 2 = Molarity after dilution C 2 = Concentration after dilution V 1 = Volume before dilution V 2 = Volume after dilution

37. Steps that should be taken in preparation of solution :

38. Example: Prepare 100mL of 1.0M hydrochloric acid, HCl from concentrated (1.21M) hydrochloric acid, HCl .   Solution: M 1 V 1 = M 2 V 2 (12.1M)(V 1 ) = (1.0M)(100mL) V 1 = 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 .

39. 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.

40. Thank you… For listening and your attention…