common experiments Flashcards
Investigating the Energy in Fuels
what are ?
These are calorimetry experiments that usually test the energy in different alcohols.
The efficiency of fuels can be analysed by comparing the amount of energy they release during combustion.
Investigating the Energy in Fuels
method and drawing
Method:
Measure the mass and initial temperature of the water
Fill the spirit burner with test substance and measure and record its mass
Stir the water constantly with the thermometer and continue heating until the spirit burner burns out
Measure and record the highest temperature of the water
Investigating the Energy in Fuels
calculation
Calculation:
Temperature change of water = final temperature – initial temperature
Number of moles burned = change in mass ÷ molecular mass
Amount of energy = change in temperature x mass of water x specific heat capacity
Amount of energy per mole (J mol-1) = total amount of energy ÷ moles burned
There are several factors that can affect the rate of a reaction. These are:
Surface area of solid reactants
Concentration of the reactants
Temperature at which reaction is carried out
The use of a catalyst
The influence of light on photochemical reactions
Experiment 2a: Surface Area
method and drawing for every passage
Method:
Add dilute hydrochloric acid into a conical flask
Use a capillary tube to connect this flask to a measuring cylinder upside down in a bucket of water (downwards displacement)
Add calcium carbonate chips into the conical flask and close the bung
Measure the volume of gas produced in a fixed time using the measuring cylinder
Repeat with different sizes of calcium carbonate chips (solid, crushed and powdered)
Experiment 2b: Concentration drawing for every passage and method
Method:
Measure 50 cm3 of Sodium Thiosulfate solution into a flask
Measure 5 cm3 of dilute Hydrochloric acid into a measuring cylinder
Draw a cross on a piece of paper and put it underneath the flask
Add the acid into the flask and immediately start the stopwatch
Look down at the cross from above and stop the stopwatch when the cross can no longer be seen
Repeat using different concentrations of Sodium Thiosulfate solution (mix different volumes of sodium thiosulfate solution with water to dilute it)
Experiment 2c:Temperature
Method:
Dilute Hydrochloric acid is heated to a set temperature using a water bath
Add the dilute Hydrochloric acid into a conical flask
Add a strip of Magnesium and start the stopwatch
Stop the time when the Magnesium fully dissolves
Repeat at different temperatures and compare results
Experiment 2d: Catalyst
Method:
Add Hydrogen Peroxide into a conical flask
Use a capillary tube to connect this flask to a measuring cylinder upside down in a bucket of water (downwards displacement)
Add the catalyst Manganese(IV) Oxide into the conical flask and close the bung
Measure the volume of gas produced in a fixed time using the measuring cylinder
Repeat experiment without the catalyst of Manganese(IV) Oxide and compare results
Determining the Formulae of Metal Oxides
Common metals uses in these experiments include
There are two methods to carry out this investigation.
copper, magnesium and calcium.
Combustion of Metal Oxide
Reduction of Metal Oxide
Experiment 3a: Combustion of Metal Oxide
method draw passages calculation
Method:
Measure and record the mass of crucible and lid
Add sample of metal into crucible and measure mass with lid and record
Strongly heat the crucible over a bunsen burner for several minutes
Frequently lift the lid to allow sufficient air into the crucible for the metal to fully oxidise but without letting any of the gaseous metal oxide to escape
Continue heating until the mass of crucible remains constant
Measure the mass of crucible and contents and record
Calculation of empirical formula:
Mass of metal = (mass of crucible + lid + metal) – (mass of crucible + lid)
Mass of metal oxide = (mass of crucible + lid + oxide) – (mass of crucible + lid)
Mass of oxygen = mass of metal oxide – mass of metal
Step 1 – Divide each of the two masses by their Relative Atomic Masses
Step 2 – Simplify the ratio
Metal Oxygen
Mass x y
Mole x / Mr y / Mr
= a = b
Ratio a : b
Step 3 – Write out the formula using the ratio e.g. for magnesium: MgaOb
Experiment 3b: Reduction of Metal Oxide
method draw passages calculation
Method:
Measure and record the mass of the metal oxide
Use a clamp to hold boiling tube horizontally, and place the metal oxide at the end of the tube
Heat using a bunsen burner until all the oxide has completely changed colour, indicating that all oxygen has been reduced
Measure mass and record mass of the remaining powder
Calculation of empirical formula:
Mass of metal = mass of remaining metal powder
Mass of oxygen = (mass of metal oxide) – (mass of metal powder)
Step 1 – Divide each of the two masses by their Relative Atomic Masses
Step 2 – Simplify the ratio
Metal Oxygen
Mass x y
Mole x / Mr y / Mr
= a = b
Ratio a : b
Step 3 – Write out the formula using the ratio e.g. for copper: CuaOb
Investigating Solubility of Salts
The solubility of a solid is the…
The solubility of a substance in water at different temperatures ….and can be plotted on a graph to produce a…
amount of that solid that you can get to dissolve in a fixed amount of water at room temperature.
changes
solubility curve.
Experiment 4: Investigating Solubility of Salts
method, draw passages
Method:
Set water bath to specific temperature
Use water from water bath and add to beaker, making sure to use a thermometer to record the exact temperature of the water in the beaker
Record mass of the salt and add to the beaker
Measure time taken for the salt to dissolve and record
Repeat the experiment for different solids at different temperatures
Experiment 4: Investigating Solubility of Salts
results, graph
Results:
Generally most solids become more soluble as the temperature increases.
This is why sugar dissolves better in hot water than in cold water.
The graph below shows the solubility curves produced from the investigation of the solubility of NaCl, KNO3 and PB2(NO3) at 20ºC, 30ºC and 40ºC.
Solubility curves can be used to compare solubilities of different compounds and to predict the yield produced on crystallisation.
This can be done by extrapolation.
Performing an Acid-Base Titration
Acid base titrations are the most common kind of titration.
You may be asked to calculate the moles present in a given amount, the concentration or volume required to neutralise an acid or base.
Titrations may also be used to
prepare salts or other precipitates and in redox reactions or to prepare complexes.
Experiment 5: Performing an Acid-Base Titration
method draw passages
Method:
Place the conical flask on a white tile so the tip of the burette is inside the flask
Add a few drops of a suitable indicator to the solution in the conical flask
Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously
Quickly close the tap when the end-point is reached (sharp colour change) and record the volume (being sure that you place your eye level with the meniscus)
Now repeat the titration with a fresh batch of alkaline
As the rough end-point volume is approached, add solution from the burette one drop at a time until the indicator changes colour
Record the volume to the correct number of decimal places (to 0.1cm3)
Repeat until you achieve two concordant results (two results that are within 0.1cm3 of each other)
Experiment 5: Performing an Acid-Base Titration
calculations
Make sure you balance the chemical equation before performing the calculations
Use the general formulae below and rearrange it to calculate what the question is asking you to find:
common error when performing titrations is to leave the funnel on the top of the burette after filling.
This is a source of error as
liquid may drip into the burette after it has been calibrated, resulting in inaccuracy.
The common indicators and their colours
A common error is to suggest using Universal Indicator as a suitable indicator for an acid-base titration.
This is incorrect as a
sharp colour change is required to identify the end-point, which cannot be achieved with Universal Indicator.
Preparing soluble salts
There are two methods of preparing soluble salts
Preparation of Soluble Salts by adding Acid to a solid Metal, Base or Carbonate+
Preparation of Soluble Salts by reacting a Dilute Acid and Alkali
Experiment 6a: Preparation of Soluble Salts by adding Acid to a solid Metal, Base or Carbonate
draw passagees and write method
Method:
Add dilute acid into a beaker and heat using a bunsen burner flame
Add the insoluble metal, base or carbonate, a little at a time, to the warm dilute acid and stir until the base is in excess (i.e. until the base stops disappearing and a suspension of the base forms in the acid)
Filter the mixture into an evaporating basin to remove the excess base
Heat the solution to evaporate water and to make the solution saturated. Check the solution is saturated by dipping a cold, glass rod into the solution and seeing if crystals form on the end.
Leave the filtrate in a warm place to dry and crystallize
Decant excess solution and allow crystals to dry
Experiment 6b: Preparation of Soluble Salts by reacting a Dilute Acid and Alkali
method and draw passages
Method:
Use a pipette to measure the alkali into a conical flask and add a few drops of indicator (phenolphthalein or methyl orange)
Add the acid into the burette and note the starting volume
Add the acid very slowly from the burette to the conical flask until the indicator changes to appropriate colour
Note and record the final volume of acid in burette and calculate the volume of acid added (starting volume of acid – final volume of acid)
Add this same volume of acid into the same volume of alkali without the indicator
Heat to partially evaporate, leaving a saturated solution
Leave to crystallise decant excess solution and allow crystals to dry
Preparing insoluble salts
Insoluble salts can be prepared using…
The solid salt obtained is the …thus in order to successfully use this method the solid salt being formed must be….
a precipitation reaction.
precipitate,
insoluble in water.
Using Two Soluble Reactants
Experiment 6c: Preparation of Insoluble Salts
method and draw passages
Method:
Dissolve soluble salts in water and mix together using a stirring rod in a beaker
Filter to remove precipitate from mixture
Wash filtrate with water to remove traces of other solutions
Leave in an oven to dry
Selecting a method of preparationWhen deciding the method of preparation, if is important to first know whether the…
If it is soluble than it can be prepared using either method (A or B) for preparing a soluble salt.
If it is insoluble then it must be prepared using by ….
salt being produced is soluble or insoluble.
precipitation.
Experiment 7: Investigating the Conditions for Rusting
….must be present for rust to occur
Rusting is a …process and it occurs faster in …since the presence of…
Oxygen and water must be present for rust to occur
Rusting is a redox process and it occurs faster in salty water since the presence of sodium chloride increases the electrical conductivity of the water.
Experiment 7: Investigating the Conditions for Rusting
METHOD AND IMAGE AND RESULTS
Method:
Set up the apparatus as shown in the diagram
The water in test tube 2 is boiled to remove any dissolved oxygen
Leave the apparatus for a few weeks
Results:
The nail on the left rusts as it is in contact with both air ( which contains oxygen) and water
The nail in the middle does not rust as it is not in contact with air
The nail on the right does not rust as it is not in contact with water (calcium chloride absorbs any water molecules present due to moisture)
The results prove that both air and water must be present for rusting to occur
Corrosion and rust are not the same process.
Corrosion is…whereas rusting is…
Corrosion and rust are not the same process.
Corrosion is the general term used to describe the degradation of metal surfaces whereas rusting is the specific type of corrosion that happens to iron in the presence of oxygen and water.
Experiment 8: Investigating the Percentage of Oxygen in Air
Experiment 8a: Investigating the % of O2 in Air using Iron
method and image ,results, calculations
Method:
Place wet iron filings at the end of a burette using vaseline to hold them in position
Use a clamp to hold the burette vertically in the trough of water
Record starting height of water in burette and leave apparatus for several days
Measure and note the final height of water level in the burette
Results:
The water level rises to replace the volume of oxygen lost during reaction to form iron(II) oxide
A constant level is reached when there is no more oxygen left
Calculations:
Volume of air at the start = (total burette Volume – initial burette reading)
Volume of oxygen reacted = (initial reading – final reading)
Percentage of O2 in air = (volume of oxygen used ÷ volume of air at start) x 100
Experiment 8b: Investigating the % of O2 in Air using Combustion
methods, results and calculations
Method:
Pace phosphorus into an evaporating dish and place it on a trough of water
Ignite phosphorus and cover evaporating dish with a bell jar
Measure and note the starting height of the water level in the bell jar
Leave apparatus for some time
Measure and note the final height of the water level in the bell jar
Results:
The water level rises to replace the volume of oxygen lost during combustion
A constant level will be reached when all of the oxygen has been consumed
Calculations:
Change in height of water = (final height – starting height)
Percentage of O2 in air = (change in height ÷ final height) x 100
Experiment 9: Investigating the Products of Combustion
These tests are performed on ….to investigate the products of…
hydrocarbon
complete combustion.
Experiment 9: Investigating the Products of Combustion
image, method
Method:
Set up the apparatus as shown in the diagram, placing ice around the first boiling tube
The first boiling tube contains cobalt chloride and the second contains limewater
As the gas from the combustion reaches the first boiling tube, any water present will condense on cooling and turn the cobalt chloride paper from blue to pink
The second boiling tube will turn clear to cloudy, indicating the presence of carbon dioxide
H2O and CO2 are the expected products of the complete combustion of a hydrocarbon
