GEN CHEM 1 | Lab Operations

Reagent Bottles

dark colored bottles that protect chemicals from light; chemicals are obtained using a spatula

Transferring Solid Chemicals into Test Tubes

1. Fold a clean rectangular piece of paper lengthwise.

2. Put the solid reagents at the edge of the paper.

3. Hold the test tube in a horizontal position and slide the paper in until it touches the bottom of the test tube.

4. Incline the tube and gently tap the paper to ensure that the reagent reaches the bottom and not the sides.

Electronic Balances

allows one to quickly measure the mass of a substance with a high level of accuracy.

Tare/Zero Button

After placing a container on the scale, pressing this resets the scale to zero. This lets you place the reagents into the container and provides you an accurate measurement, since the mass of the container is no longer accounted for.

Ways to Transfer Liquid Reagents

1. Make the neck of the container the reagent is in must touch the receiving vessel.

2. Lean the neck on to a stirring rod, especially in narrow mouth containers.

3. Use a medicine dropper or pipette to transfer small amounts of liquids.

Measuring Liquid Substances

Pour the liquid into a graduated cylinder until the liquid meniscus is at the desired measurement. Base the volume’s value on the line aligned with the liquid meniscus, and add an additional significant figure at the end of the known measurement.

Liquid Meniscus

the lowest point of a curved surface when measuring its volume in a graduated cylinder

Measuring the Volume of an Irregular Object

1. Pour some liquid into a graduated cylinder and record the initial volume.

2. Place the object inside and record the new volume. It should be higher than the initial due to water displacement.

3. Get the difference between the two values.

Gas Valve

contains and controls the amount of gas relayed to the burner

Hose

is how the gas travels from the gas valve to the needle valve

Needle Valve

controls the quantity of gas admitted to the burner

Air intake openings

how air needed for combustion enters burner

Collar

small disk at the bottom that is turned to control the amount of air entering the barrel

Base

support for the burner

Barrel

raises the flame to a suitable height for heating; it is where gas and air mix for combustion

Inner Blue Cone

The most visible part of the flame, which contains the hottest region at the tip

Outer Nonluminous Flame

the lighter part of the flame

Safety Flame

It is color yellow/orange. It is the coolest at 300 degrees, and it merely indicates that the burner is on.

Blue Flame

Also known as an invisible flame, it is difficult to see and is the kind of flame that is usually used. It is around 500 degrees.

Roaring Blue Flame

It is the hottest flame at 700 degrees and makes noise. It has a blue triangle at the center

Using the bunsen burner

• Align the the lever for the gas with the hose.

• Light the burner and turn on the gas control at the same time.

• Slowly open the air holes.

• Use the collar to adjust the flame’s color and the needle valve to adjust height.

• To close the bunsen burner, turn off the air holes followed by the gas control.

Heating Set-Up

A bunsen burner is placed at the bottom of a ring stand. The ring is fastened to the pole of the ring stand. If a glassware needs to be suspended using an iron clamp, it should not be too fastened to prevent the expanding glassware from breaking.

Heating a Beaker

A wire gauze is placed on the ring. Then, the beaker with the reagent is placed on top of the wire gauze.

Heating with a Crucible

Place a clay triangle on the iron ring. Then, place a crucible containing the reagent on top of the clay ring and cover it.

Heating a Test Tube

Hold the test tube with a test tube holder at an angle of 45 degrees over the flame. Heat the reagent by slowing passing the bottom part back and forth over the flame.

Preparing Fluted Filter Paper

1. Fold the circular paper in half three times in the same direction until you have a 1/8 section cone.

2. Unfold the paper twice to get a semicircle.

3. Alternately fold up and down every eighth of the semicircle to create a fan-fold.

4. Open the fan until you get a fluted filter cone, similar to a shell.

5. Find the two opposing ends that are not folded properly and fold them inward.

Titration

A solution with a known concentration called the titrant is dispensed by a burette and reacts with a solution with an unknown concentration called the analyte. It helps you know how much of the titrant is needed to neutralize a solution, usually used in acid-base reactions.

End Point of a Titrant

Indicates when titration is complete through the change of color of an indicator solution

Equivalence Point of a Titrant

when the number of moles of the titrant and analyte are equal

Steps in Titration

1. Rinse the inside of the burette with the titrant at least twice.

2. Once dry mount it to the ring stand with the burette clamp.

3. Place a beaker with the analyte under the solution. Add some of the indicator solution

4. Fill the burette to above the zero mark.

5. Run some solution through the stopcock to fill the burette tip completely.

6. Record the starting volume.

7. When titration is over, record the final volume.

8. Get the difference between the two volumes to know how much solution was added.

Distillation

It is used to separate the components of a liquid mixture. By separating them based on boiling points.

Boiling Flask

This is where the mixture is heated.

Liebig condenser

The vapor of one of the liquid components is cooled back into liquid using the cooling water.

Receiving Flask

This is where the liquid with the lower boiling point goes.

Distillation Column

It is used to separate the two substances through heating and cooling.

Steps in Distillation

1. Attach the boiling flask with the mixture onto the clamp stand using the clamp. Place the bunsen burner under it, and place the thermometer in the flask to monitor the temperature.

2. Attach the distillation column to the boiling flask and the condenser to the distillation column. Place the receiving flask at the other end of the condenser.

3. Heat the boiling flask. Use the thermometer to slowly adjust the heat if needed.

4. Collect the distillate as it drips into the receiving flask.