Experimental procedure and experiments Flashcards
Give an example of how we could identify a polar molecule?
We can run the liquid through a burette or a tap and place a charged rod next to the flow of the liquid, the charged rod will cause the polar molecule to be deflected whereas a nonpolar molecule will not be affected by the presence of the charged rod
Give an example of apparatus that we could use to measure viscosity of a liquid?
We can measure how long a ball takes to travel through a liquid, assuming the temperature is constant the liquid with a lower viscosity will allow the ball to fall through it more quickly than if the liquid had a higher value of viscosity.
Describe the process of Titration?
Titration is an experimental technique that allows us to determine the concentration or mass of a chemical substance.
The chemical used to analyze the chemical can be placed in the burette and filled up to the graduation mark. the chemical and should fill the burette and left to run until it reaches the graduation mark the bottom of the meniscus should touch the graduation mark)
The analyte is the chemical that is being analysed and an accurately known volume of the analyte should be measured out using a pipette and placed in a conical flask.
The tap of the burette should then be opened and the reaction will continue until an end point is reached indicated by the change in the colour of the pH indicator added to the conical flask before the reaction except from if the reaction is self indicating. We should place a while tile beneath the conical flask to easily identify when the end point of the reaction has been reached.
Describe how esters can be made in the lab?
Esters can be made in the lab by
- placing a mixture of alcohol and a carboxylic acid in a test tube.
- The test tube should then be placed in a water bath to provide the reaction with heat.
- A wet paper towel should be placed at the top of the test tube as this prevents the alcohol from evaporating out of the test tube
- The reaction will have been sucessfull when an oily layer is formed on top of the ester. This oily layer forms because most esters are not soluble in water due to their large hydrocarbon character and non-polar bonding.
Explain why using a bunsen burner would be unsuitable when producing esters?
Providing heat using a bunsen burner would be dangerous because of the presence of flammable reactants such as alcohols in the reaction mixture. Instead a water bath should be used to supply heat to the reaction
When we perform an esterification reaction an oily layer of the ester forms on top of the water how exactly are we able to seperate the two layers?
The components of the mixture can be separated using a process called distillation.
- The mixture will be heated and the liquids will evaporate when their boiling points are reached
- Since the liquids have different boiling points each liquid will evaporate at a different time
- The individual liquid that evaporates can then be condensed and collected
- Each individual liquid in the mixture will be removed one at a time in order of boiling point.
Explain how a condenser used in a distillation reaction works?
Cold water runs through the condenser which causes the hot vapour running through the condenser to condense and be converted back into its liquid form
Describe the process of reflux?
Reflux describes all of the reactants being placed in a conical flask and as heat is provided for the reaction to undergo alkaline hydrolysis a condenser should be added to prevent volatile components of the reaction from leaving the reaction mixture.
Describe an experimental setup that could be used to illustrate how alcohols oxidise?
Ceramic wool soaked in the alcohol being tested should be placed at the bottom of the test tube the oxidising agent (either copper (II) oxide or acidified potassium dichromate) should be added to the test tube and the solution should be heated. If the alcohol has undergone oxidation then the oxidising agent will undergo a colour change e.g if copper (II) oxide was used the colour change would be from black to red.
State the colour change that occurs when Copper (II) Oxide is used to indicate if an alcohol has undergone oxidation?
If oxidation has taken place Black —-> Red will be the colour change observed.
State the colour change in acidified potassium dichromate that would occur when oxidation has taken place?
The colour change seen would be (Orange —–> Green/Blue)
State the colour change that can be seen when an aldehyde is reacted with tollens reagent?
When an aldehyde reacts with tollens reagent then the colour change seen will be from colourless to the formation of a silver mirror as oxidation has taken place.
State the color change that can be observed when benedict’s solution reacts with a ketone?
Ketones do not undergo oxidation hence the benedict’s solution would remain blue and no colour change would be observed
State the colour change that would be observed when an aldehyde is reacted with benedict’s solution?
When an aldehyde reacts with benedict’s solution this will cause a colour change of ( Blue ——> Red/brown)
Describe the process of steam distillation?
- Steam is generated by boiling water
- The steam will then be passed through the plant material which has water mixed with it
- The plant material will evaporate due to its volatile molecules and the gasses will then be passed through a condenser causing the gasses to condense into liquid form and a layer of oil will form on top of the water. This oil is referred to as essential oil as it comes from the essence of the plant.
