Lab Manual 2 Sept 13

8/12/2019 Lab Manual 2 Sept 13

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Lab Manual CLB 10003/11103 Sept 2013

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LAB 2

PART I (pH METER)

Reagents/ Supplies

Beakers (250 ml) Bromthymol blue (0.25% w/v) pH indicator paper pipets (1, 5 and 10 ml) Potassium Phosphate, dibasic ( Dipotassium Phosphate, K2HPO4) Potassium Phosphate, monobasic (Monopotassium Phosphate, KH2PO4) Standard buffer, pH 4.01 Standard buffer, pH 7 Test tubes 18 150 mm Volumetric flasks 100ml Wash bottle

Equipment

pH meter

PROCEDURE

PART A: Visual Estimation of pH

1. Prepare 0.1 M solutions (100ml) of K2HPO4 and KH2PO4.2. Set up a series of twelve 18 150 mm test tubes as shown in Table A-1.2A.

SECTION OF BIO-ENGINEERING

TECHNOLOGY, UniKL MICET.


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3. To tubes 1, 3, 5, 7, 9, and 11, add 5 drops of bromthymol blue and mix. You nowhave a series of color standards covering the pH range of 5.3 to 7.73. Record your

observations. This exercise simply illustrates that indicator dyes may be useful as

pH indicators.

Section A

1.

Standardize the pH meter using the standard pH 7 buffer. Rinse the electrodesusing a wash bottle. Do not wipe the electrodes with tissues because this creates a

static electric charge on the electrodes and may cause erroneous readings.

Remove the last drop of water by carefully touching a piece of clean tissue paper

to drop.

2. Measure the pH of the standard pH 4.01 buffer. Reset the pH meter if necessary.It is most important to measure the pH with two standard buffers to ensure that

the pH meter is functioning properly over the entire pH range.

3. Measure the pH of the six solutions in tubes 2, 4, 6, 8, 10 and 12 (prepared in PartA) with the pH meter. Rinse the electrodes between readings and handle them

carefully. You may also wish to use pH indicator paper to get an idea of the pH of

the solutions. This rapid method is often accurate enough for some applications

and is especially useful for very small volumes or radioactive solutions.

4.Record your observations from Parts A and B. correlate the measured values fromPart B to the expected pH value from Table A-1.2 A.


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PART II (Preparation of Solution)

Objective

To prepare solutions with known concentration.

Equipment

250 ml Erlenmeyer flask10 ml graduated cylinder flask

Pipette

Materials

NaOH

HCl (stock)

Distilled water

Example of Experiment Procedures

PROCEDURE

PART A: Preparation of 0.4 M of 250 ml NaOH solution.

Molecular weight of NaOH is 40 g/mol.

1.Before starting this experiment, firstly calculate how many moles of NaOH you willneed. Next, calculate the mole number of NaOH using the information given (0.4M of

250 ml NaOH).

2. After finding the mole number of NaOH, calculate the mass of NaOH that you need.

3. Measure the mass of NaOH that you need by using balance.

4. Transfer NaOH into 250 ml volumetric flask.

5. Add approximately 50 ml of water and shake.

6. Then add water till the volume of the solution will become 250 ml.

7. You now have a 250 ml of 0.4 M NaOH solution.


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PART B: Preparation of 0.4 M of 250 ml HCl solution

1. Before starting experiment firstly calculate how many moles of HCl you will need for

this experiment. Next, calculate the mole number of HCl using the information given(0.4M of 250 ml HCl).

2. After finding mole number of HCl, calculate the mass of HCl that you need.

3. Percentage of the stock solution is given (36.5 %). Calculate how many grams of stocksolution contain ____ grams (your result at number 2) of HCl.

4.Now you have found the mass of stock solution that you need. Find the volume of this

solution that you need. (Density:1.2 g/ml)

5. By using graduated cylinder measure ___ ml (your result at number 4) stock solution

and transfer into 250 ml erlenmeyer flask.

6. Add water till the volume will become 250 ml.

7. You now have a 250 ml of 0.4 M HCl solution.

QUESTIONS

1. How can you prepare 1 M of 400 ml KOH solution?

2. How can you prepare 2 M of 200 ml HNO3 solution from 63 % stock solution of

HNO3 which has a density of 1.4 g/mL?


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Exercise: Complete Task 1 Task 7

Task 1

Prepare 200 ml of 40% (v/v) ethanol from 70% (v/v) ethanol.

Task 2

Prepare 200 ml of 1.0M solution of Sodium hydroxide.

Task 3

Prepare 40 ml of 0.1M solution of NaCl.

Task 4

Prepare 100 ml of 1 M Tris stock at pH 8.0

Task 5

100 ml of Cell Lysis Solution 10mM Tris, 100mM EDTA, 2 % SDS, pH 8.0

Task 6

100 ml of TNES urea 10 mM Tris-HCl pH 7.5, 125 mM NaCl, 10 mM EDTA pH 7.5,0.5% SDS, 4M Urea.

Task 7

70% (v/v) isopropanol solution

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Lab Manual 2 Sept 13