Lesson 1 Introduction to Analytical Chemsitry Laboratory

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Analytical Chemistry

It is the science of obtaining, processing, and communicating information about the composition and structure of matter.

Analytical chemistry

It is the art of science of determining what matter is and how much of it exists.

Reaction

A change in which one or more chemical elements or compounds (the reactant) form new compounds (the products; manifestation)

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Note: All reactions are to some extent reversible; In many cases the extent of this back reaction is negligibly small, and the reaction is regarded as irreversible.

Reagent

A substance used in a chemical reaction to detect, measure, examine or produce other substances.

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Chemical that cause a reaction and that reaction is the composition/characteristic.

Precipitate

It is any insoluble substance that is produced after a certain reaction.

Residue

It is a portion of a solid remaining after partial solution by a reagent. A quantity or body of matter remaining after evaporation, combustion, distillation, etc.

Filtration

The act or process of filtering, especially the process of passing a liquid or gas, such as air, through a filter in order to remove solid particles.

Test Solution

A solution of some reagent, in definite strength (specific concentrations), used in chemical analysis or testing

Clear solution

Is one that is not turbid or cloudy

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No precipitation

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But “clear” if it has a color

Colorless solution

One that is not colored.

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Note: Do not use “clear” to mean “colorless”

Test

A —— is a laboratory procedure designed to show the presence or absence of some substances.

Positive test

Indicates that the substance is present

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Example:

• Formation of precipitate of distinctive color or texture.

• The dissolution of a precipitate

• The appearance of disappearance of a color in a solution or in a flame.

• The evolution of a gas

• The development of a characteristic odor.

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Negative test

Indicates that the substance is absent

Blank test

Test carried out under specified conditions with all reagents with exception of determined substances to account for consent of this substance in reagents used

Control test

A blank test to which a known sample of the ion under consideration has been added.

Specific test

A test given by one and only substance.

Centrifugation

A process that involves the use of the centrifugal force for the separation of mixtures, used in industry and in laboratory settings

Common apparatus in AnalChem

• Aspirator
• Wash bottle
• Analytical balance
• Burette
• Desiccator
• Pipette
• Burette stand

• Casserole
• Cobalt glass
• Erlenmeyer flask
• Centrifuge
• Triple beam balance

• Volumetric flask

• Thermometer

• Beakers

• Graduated cylinder

How to balance

1. Keep the balance clean
2. Always zero the balance before weighing.
3. Use a beaker or weighing boat instead of placing any kind of substances directly on the balance pan.
4. Recheck to confirm that the balance is still zeroed after use.

Use of the thermometer

* Laboratory thermometers are not to be shaken.
* Immerse bulb of the thermometer in the substance, for which you are to measure the temperature, allow the mercury to stabilize and read thermometer.
* Study the calibrations.
* Do not use it to stir.
* Kindly inform the instructor if thermometer breaks.

Using the Fume Hood

Reactions that involves production of hazardous fumes are conducted in the fume hood.

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Obtaining Liquid from a bottle

grasp the cover between the third and fourth fingers, with palms up, and while holding the cover in this fashion, pour from the bottle.

Obtaining Solids from a Bottle

* To obtain a solid, unscrew the cap of remove the cork or stopper.
* Rotate and tilt the bottle at the same time to dispense the solid slowly to a weighing boat or a clean dry container.
* Do not take reagent bottles to your working tables.
* Do not take more than what is required.
* Never return unused solids to the reagent bottle.

Safety in Heating Liquids

* When heating liquids in test tubes, always point the open end of the test tube away from yourself and anyone.
* When heating liquids in beakers, stir the liquid while carefully heating to avoid bumping. Note: Uneven boiling can cause dangerous spattering of large quantities of hot liquid.

Evaporation of solutions

* Evaporation should be carried out in small porcelain casserole.
* It should be heated over a small flame.
* In evaporating to dryness, remove the casserole from the flame while there is still a drop or two of liquid left.
* The heat from the vessel is usually enough to complete the drying.
* If additional heat is required, warm the casserole gently to avoid dry heating the reside.

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Identification of containers

When several test tubes or other containers are used in the same experiment, or when solutions are to be saved from one lab period to the next, label the containers carefully and neatly

Mixing Solutions

* Each drop of reagent added should be mixed with the solution before the next drop is added.
* Observe the effect of each drop of reagent as it is added and mixed into the solution.
* When a test tube is less than half full, mixing can usually be accompanied by shaking or flicking the tube. • Shaking a closed tube with or finger results in thorough mixing of the contents, but danger of contamination from the cork or injury to the finger, making this technique impractical.

Regulation and Testing of Acidity

* To determine the acidity of a solution, indicators or indicator papers are used.
* Place the indicator paper on a watch glass and then drop or two of the solution.

Flame test

The flame test is used to visually determine the identity of an unknown metal or metalloid ion based on the characteristic color the salt turns the flame of a Bunsen burner

Classic Wire Loop Method

* Use a clean nichrome wire loop.
* The wire loop must be cleaned by dipping it in HCl or HNO3 followed by rinsing with distilled water or deionized water.
* The loop must be cleaned between tests.
* The clean loop is dipped in wither a powder or solution of an ionic salt, exposed to the blue part of the flame and the resulting color is observed.

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Precipitation with Hydrogen sulfide

* Hydrogen sulfide is the most useful reagent in qualitative analysis.
* In acidic solution, it is the group reagent for the copper-arsenic group of ions.
* In basic solution, it is the group reagent for iron-aluminum group of ions.
* Thioacetamide is recommended as the source of hydrogen sulfide in the laboratory.

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Note: Group 1 to 5 cations and anions will be discussed or used in anachem.

Separation of Solid from a Liquid

* The separation of a solid from a liquid can be accompanied either by centrifugation or by filtration.
* Centrifugation is more rapid and leaves the solid in a test tube were it may be treated with the next reagent.
* Filtration leaves the precipitate spread over a circle of paper from which it must be transferred to some vessel.

Washing the precipitate on the filter paper

* Wash the precipitate with a jet of distilled water or wash solution from a capillary syringe.
* Begin the washing at the upper edge of the paper.
* If possible, loosen the precipitate, from the paper with the jet and work it toward the apex.

Transferring Precipitates from the Filter (If the precipitate is soluble in the first reagent,)

* If the precipitate is soluble in the first reagent, it may be dissolved by dropping the reagent over the precipitate on the filter.
* Puncturing a small hole through the apex with a pointed glass rood and then washing the precipitate into the receiving vessel with a fine stream of water from a wash bottle.
* You may remove the filter paper from the funnel, unfolding and holding the paper in inclined position over a casserole and washing the precipitate in the receiving vessel.

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Transferring precipitates from the filter // If the precipitate is appreciable quantity and is allowed to buy

* If the precipitate is in appreciable quantity and is allowed to dry, the bulk of it may be scraped from the paper with a spatula and the small amount retained on the paper may be washed off.
* If the amount of the precipitate is small, tear off and discard those portions of the filter paper that are free of precipitate and place the remaining paper carrying the precipitate in a reagent that dissolves it.

Reaction is made

Reactant to product and can come go back. It can also be in the state of “equilibrium”

What is the difference of precipitate and the residue?

The moment it React and it create solid substance is precipitate (product). And when you separate the precipitation or solution, it leaves a residue

Format for procedure, chu chu

Passive voice, past tense

How to transfer liquids from one bottle to another bottle?

1. place one beaker or bottle on a table.
2. place the rod inside the bottle and place it 90 degree. in the video, the rod is placed at the middle of the bottle.
3. Pour the liquid from the other bottle to the rod.
4. watch as the rod guides the liquid safely to the other bottle.

Reagent blank

contains all the reagents used to prepare the sample

Matrix blank

similar in chemical composition to the sample but without the analyte

Titration

A method of volumetric analysis in which a volume of one reagent (the titrant) is added to a known volume of another reagent slowly from a burette until an end point is reached. The volume added before the end point is reached is noted.

Indicator

A substance that is used to determine how acidic or alkaline a solution is by changing color. The most common indicator is litmus paper, but others include methyl orange and universal colors.

Universal indicator

An indicator which indicates a wide variety of pH values by displaying several different colors.

End point

the point during a titration when an indicator shows that the amount of reactant necessary for a complete reaction has been added to a solution or a known pH point of an acid and base interaction as shown by a chemical indicator change in color.

pH Scale

A logarithmic scale \[ from 1 (acid) to 14 (base)\] for expressing the acidity or alkalinity of a solution. a pH of below 7 indicates an acid solution; one above 7 indicates alkaline solution. More accurately, the pH depends not on the concentration of hydrogen ions but on their activity, the pH depends not on the concentration of hydrogen ions but on their activity, which can be measured experimentally. pH stands for “potential of hydrogen”. The scale was introduced by S.P. Sorensen in 1909.