Ochem lab midterm

When using acids and bases, note that these substances are _____________ Make every effort to avoid contact with _________________ Be sure to wipe up any spills ____________

corrosive, the skin and lab surfaces, immediately

Complete each statement on safety precautions when using round bottom flasks. Before using the flask, inspect it for _____________ Use______________ for stability when suspending the flask on a ring stand. Never heat a flask that is _____________

cracks or imperfections, a clamp, closed

After assembling a gravity filtration apparatus, begin the separation of a mixture by __________ it into the filter paper. Pour the entire contents of the mixture into the filter paper, ____________ the solid in the filter paper if needed to speed up the filtration. After all the liquid has drained through the filter paper, finish by rinsing the solid with _____________

decanting, stirring, solvent

In general, when hydrocarbons like oil are added to water, the two liquids _____________ because hydrocarbons are ______________ and water is ___________

do not mix, non-polar, polar

To determine the layers in a separation of organic and aqueous solutions, you can add a small amount of _____________ If the top layer is aqueous, the addition will ______________ top layer. If the bottom layer is aqueous, the addition will __________________the top layer and ___________________the bottom layer

water drops, combine with, travel through, combine with

When separating benzoic acid, naphthalene, and 3-nitroaniline, identify the solution used for each described purpose. 1. Extract aniline into the aqueous layer 2. Extract benzoic acid into the aqueous layer 3. Extract reconstituted benzoic acid out of the aqueous layer 4. Reconstitute benzoic acid from aqueous layer 5. Extract reconstituted 3-nitroaniline out of the aqueous layer 6. Reconstitute aniline from aqueous layer

1. 5% HCL solution 2. 5%NaOH solution 3. Dichloromethane 4. 6M NaOH

Before adding a sample or solvent to a separatory funnel, what should you have in place? Select one or more: 1. A stopcock in the closed position 2. A flask under the separatory funnel 3. A funnel in the top of the separatory funnel 4. A stopper in the top of the separatory funnel 5. A piece of paper under the collection flask

1. A stopcock in the closed position 2. A flask under the separatory funnel 3. A funnel in the top of the separatory funnel

If crystal growth does not start on its own after the solution in the flask returns to room temperature, identify the best ways to promote this process. Select one or more: 1. Add a bit of solid as a seed crystal. 2. Place the flask on a hot plate to evaporate some solvent. 3. Scratch the bottom of the flask gently with a stirring rod. 4. Add ice cubes to the solution.

1. Add a bit of solid as a seed crystal. 3. Scratch the bottom of the flask gently with a stirring rod.

Identify the characteristics of a good recrystallization solvent. Select one or more: 1. Dissolves a sample well at high temperatures. 2. Does not dissolve a sample well at low temperatures. 3. Does not dissolve a sample well at high temperatures. 4. Is not an organic liquid with a low boiling point. 5. Dissolves a sample well at low temperatures.

1. Dissolves a sample well at high temperatures. 2. Does not dissolve a sample well at low temperatures.

What is the visual indicator that enough of a drying agent, such as anhydrous MgSO4MgSOX4 or CaCl2CaClX2 , has been added to properly dry an organic solution? Select one: 1. The drying agent will move freely like a powder around the solution. 2. The drying agent will start floating on top of the solution. 3. The drying agent will stick to the sides of the container. 4. The drying agent will clump into the corner of the container.

1. The drying agent will move freely like a powder around the solution.

Suppose you are performing an extraction procedure with a carboxylic acid, like a benzoic or toluic acid. Which layer should contain the carboxylic acid in a two-layer mixture of water and an organic solvent, like diethyl ether? 1. The organic layer 2. Neither layer 3. The aqueous layer You then add a base to form the corresponding carboxylate. Which layer should contain the carboxylate in a two-layer mixture of water and an organic solvent, like diethyl ether? 4. The organic layer 5. The aqueous layer 6. Neither layer

1. The organic layer, 6. Neither layer

When using vacuum filtration to separate a dissolved solid from an undissolved solid, what techniques should you use to ensure a quantitative separation? Select one or more: 1. Wash the solid on the filter paper with a small amount of water. 2. Dry the solid on the filter paper after the separation. 3. Wet the filter paper before pouring the mixture into the filter funnel. 4. Carefully rinse the flask into the filter funnel with a small amount of water

1. Wash the solid on the filter paper with a small amount of water. 2. Dry the solid on the filter paper after the separation. 3. Wet the filter paper before pouring the mixture into the filter funnel. 4. Carefully rinse the flask into the filter funnel with a small amount of water

What modifications to a fractional distillation setup can be made in order to increase the speed or efficiency of the separation? Select one or more: 1. Wrap aluminum foil around the sample flask and fractionating column. 2. Place the sample flask and fractionating column in an ice bath. 3. Place the receiving flask in an ice bath. 4. Wrap aluminum foil around the receiving flask.

1. Wrap aluminum foil around the sample flask and fractionating column. 3. Place the receiving flask in an ice bath

Identify the best drying agent or process for each described purpose. 1. Storage of solvents or other materials in a desiccator 2. Removal of small amounts of water from a polar solvent 3. Removal of visible pockets of water from an organic solvent

1. drierite 2. anhydrous calcium chloride 3. brine wash

Determine whether each melting point observation corresponds to a pure sample of a single compound or to an impure sample with multiple compounds. 1. Experimental melting point is below literature value 2. Wide melting point range 3. Experimental melting point is close to literature value 4. Narrow melting point range

1. impure sample of multiple compounds 2. impure sample of multiple compounds 3. pure sample of a single compound 4. pure sample of a single compound

To prepare a sample in a capillary tube for a melting point determination, gently tap the tube into the sample with the 1._______ end of the tube down. Continue tapping until the sample 2. __________________ Then, with the 3._________ end of the tube down, tap the sample down slowly or 4.___________________ to move the sample down faster. Finally, make sure that you can see 5.__________ in the magnifier when placed in the melting point apparatus before turning on the heat.

1. open 2. is a couple millimeters high 3. closed 4. drop the tube into a longer tube 5. some or all of the solid

What is the recommended order of measurements to report the most accurate melting point possible? 1. Use slow heating to confirm the careful measurement. 2. Use quick heating to estimate the melting point. 3. Use slow heating to carefully observe melting.

1. third step 2. first step 3. second step

Washes and extractions are both techniques that use a separatory funnel to separate liquid layers. However, washes and extractions have differences. 1. Leaves desired compound in its starting layer 2. Moves desired compound from one layer to another 3. Leaves impurities in their starting layer 4. Often involves a reaction in one of the layers 5. Moves impurities from one layer to another

1. wash 2. extraction 3. extraction 4. extraction 5. wash

Why should you use a finely ground solid when determining the melting point of a sample? Select one or more: 1. Only fine samples will fit into the melting point capillary tubes. 2. Air pockets in a coarse sample could disrupt heat distribution. 3. Uniform, small particles heat more consistently throughout the sample. 4. The melting of coarse samples cannot be viewed by the devices.

2. Air pockets in a coarse sample could disrupt heat distribution. 3. Uniform, small particles heat more consistently throughout the sample.

Identify the characteristics of a good recrystallization solvent. Select one or more: 1. Dissolves a sample well at low temperatures. 2. Dissolves a sample well at high temperatures. 3. Does not dissolve a sample well at low temperatures. 4. Does not dissolve a sample well at high temperatures. 5. Is not an organic liquid with a low boiling point.

2. Dissolves a sample well at high temperatures. 3. Does not dissolve a sample well at low temperature

What is the best course of action if solid material remains in the flask after the heating step of a recrystallization? Select one: 1. Redo the heating step of the recrystallization. 2. Filter the hot mixture. 3. Allow the mixture to cool, then filter the mixture. 4. Remove the solid with a spatula.

2. Filter the hot mixture.

When melting mixtures of compounds, what is the eutectic composition? Select one: 1. The melting point of each pure substance 2. The mixture composition with the lowest melting point 3. The melting point when the mixture has a 50:50 composition 4. The mixture composition with the average melting point of the two pure compounds

2. The mixture composition with the lowest melting point

What are the concerns presented by overheating a distillation to a dry flask? Select one or more: 1. The dry flask might become brittle and could easily be broken. 2. The remaining solid residue might contain explosive peroxides. 3. The empty glassware might heat quickly, igniting vapors from the distillation. 4. The lack of liquid in the original flask might reverse the distillation process.

2. The remaining solid residue might contain explosive peroxides. 3. The empty glassware might heat quickly, igniting vapors from the distillation.

Why might activated carbon be added to a sample during the recrystallization process? Select one: 1. To act as a seed crystal when the solid sample is not recrystallizing 2. To absorb impurities causing the recrystallization solution to have an incorrect color 3. To help the sample dissolve into the recrystallization solvent at low temperatures 4. To help catch the purified sample on the filter paper after recrystallization

2. To absorb impurities causing the recrystallization solution to have an incorrect color

What hazards are associated with phenacetin? Select one or more: 1. Phenacetin produces nauseating vapors. 2. Phenacetin is highly reactive. 3. Phenacetin is slightly flammable. 4. Phenacetin is carcinogenic.

3. Phenacetin is slightly flammable. 4. Phenacetin is carcinogenic.

What characteristics should a good sample for melting point determination have? Select one or more: 1. Liquid phase 2. Large clumps 3. Small particles 4. Thoroughly dry 5. Solid phase

3. Small particles 4. Thoroughly dry 5. Solid phase

You can separate a mixture of sand and copper(II) sulfate pentahydrate using filtration. What difference in properties enables the separation of the two solids by filtration? Select one: 1. The hydrate has a lower boiling point than the sand. 2. The hydrate has a higher density than the sand. 3. The hydrate is soluble in water but the sand is not. 4. The hydrate is blue but the sand can be many colors

3. The hydrate is soluble in water but the sand is not.

Under what condition should fractional distillation be used instead of standard distillation for the separation of two liquids? Select one: 1. When the boiling points of the liquids are far apart 2. When separating an organic liquid from an inorganic liquid 3. When the boiling points of the liquids are close 4. When one liquid is completely miscible with the other

3. When the boiling points of the liquids are close

When performing a melting point determination, how should you report your findings? Select one: 1. As the temperature when you first notice the appearance of liquid in the sample 2. As the temperature when the last bit of solid melts into liquid 3. As the average between the temperatures when melting starts and when it ends 4. As a range from the temperature when melting starts to the temperature when it ends

4. As a range from the temperature when melting starts to the temperature when it ends

What is meant by the term bumping? Select one: 1. Suddenly increasing the temperature on a liquid 2. Agitating a liquid with a stir bar or stirring rod 3. One liquid coming in contact with another 4. Sudden and uncontrolled boiling of liquid

4. Sudden and uncontrolled boiling of liquid

What is the purpose of a drying agent in the work up of an organic reaction? Select one: 1. To absorb the organic compound from the organic solution 2. To remove colorful impurities from an organic solution 3. To remove the organic solvent from the organic solution 4. To absorb small amounts of water in an organic solution

4. To absorb small amounts of water in an organic solution

Sulfuric acid, H2SO4HX2SOX4 , is an important industrial chemical, typically synthesized in a multi-step process. What is the percent yield if a batch of H2SO4HX2SOX4 has a theoretical yield of 3.4 kg, and 2.7 kg are obtained at the end of the process?

79%

Identify items that can be used to control the boiling when heating liquid in a round bottom flask. Select one or more: A Bunsen burner A rubber stopper or cork A stir bar and stir plate Boiling chips or stones

A stir bar and stir plate Boiling chips or stones

Identify heating apparatuses suitable for use with round bottom flasks. Select one or more: Oil bath Hot plate Heating mantle Water bath

Oil bath Heating mantle Water bath

Which property is the basis of the purification technique recrystallization? Select one: Polarity Color Molecular weight Solubility

Solubility

Aniline involves an amine, which is a______________ When an aqueous acid solution is added to an organic solution including aniline, the aniline appears in the ________________layer in its________________form. Then, a base is added to __________________the aniline.

basic functional group, aqueous layer, protonated, reconstitute

In addition to specialized glassware and tools, there are several other considerations required for the setup of a distillation apparatus. Before assembling a distillation apparatus, lubricate the ground glass joints of each piece of glassware using ____________ This helps seal the connection between two components. Once two components are fit together, use __________________ to make the connections secure. Stabilize the complete distillation setup using a ______________________

grease, clamps, ring stand

At the melting point, the solid form of a substance ______ the liquid form of the substance.

is in equilibrium with

In order to dissolve a chemical sample in a recrystallization solvent, add the room-temperature solvent _______________ in an Erlenmeyer flask on a hot plate. Turn on the heat, starting at ____________ Using a ____________, add additional solvent from a second container on the heat source. Swirl the sample flask after each addition, and try to add _____________ in order to dissolve the solid.

just until it covers the sample, a low setting and increasing gradually, pipet, as little solvent as possible

fter a recrystallization, a pure substance will ideally appear as a network of _____________ __________ If this is not the case, it may be worthwhile to reheat the flask and allow the contents to cool more _______________

large crystals, slowly

Distillation is the separation of multiple___________ components based on their different__________________ As the mixture is heated and the first component_________________, its _______________ form travels through the distillation set-up and _____________________ into a different container. __

liquid, boiling points, boils, vapor, condensdes

After a mixture has been poured through filter paper, the __________ component remains on top while the _____________ flows through. To collect the solid, spread the filter paper ______________ and allow the solvent to __________

solid, liquid, on a watch glass, evaporate