Due to the sheer amount of content to be shared on Tips for JC A-Level H2 Chemistry Paper Practical Exam 2019, I have split them into 2 blog posts.
In case you have missed out on the previous post on Tips for JC A-Level H2 Chemistry Paper 4 Practical Exam 2019 – Part 1, you are highly encouraged to check it out. We have discussed on the format, marks allocation and weightage of H2 Chemistry Paper 4 Practical Exam as well as the Chemistry Concepts in key topics which students need to know before they embark on their Chemistry Practical exam.
Today, we shall continue with Part 2 and specifically look at the section on Planning (P) questions, on how to plan an experiment in the H2 Chemistry Practical Exam.
It is usually not a major problem for students to diligently follow a detailed set or sequence of instructions and use techniques, apparatus and materials safely and effectively, in order to obtain the necessary experimental data.
However, many Chemistry students actually do not understand the purpose and rationale of each experimental step which they are performing as well as the why certain quantities or apparatus is being used.
As such, many a times, students struggle when it comes to Planning An Experiment in their Chemistry Practical Exam. They are usually at a loss as how to even start the Planning question.
Tips for Planning Questions in A-Level H2 Chemistry Practical Exams
I will share the tips in Planning Questions in two sections:
- Main components of a Planning Question
- Possible Planning Questions for 2019 H2 Chemistry Practical Exam (Paper 4)
Let’s get started.
A) Main components of a Planning Question
1. Introductions and Aim of Experiment
You are encouraged to read the given question carefully and understand the aim of the experiment. It is almost always given towards the end of the question.
2. Theory
You need to identify the topic (e.g. Chemical Energetics, Reaction Kinetics, etc).
You need to define the problem and give a theoretical basis of why a certain method is being used.
You need to give an outline of the proposed method.
It is unlikely to be asked to write about the extensive Chemistry principles associated with the experiment.
However, students may be asked to state the dependent variable and the independent variable for the experiment.
3. Pre-Experiment Calculations
It is almost confirmed that you will be tested in every Planning questions, so ensure that you can do basic mole calculations.
You will be asked to work out appropriate quantities of reagents (masses or volumes) to be used in the experiment.
You may be required to write a balanced chemical equation for the reaction. Perhaps, more than one equation if necessary i.e. back titrations
You are also expected to state any assumptions made.
4. Experimental Procedure
This is also almost confirmed that you will be tested in every Planning question.
You will be asked to give the proposed experimental procedure by giving detailed sequence of steps to be carried out in order to collect the experimental data.
You need to state all the apparatus used and their capacities if necessary.
The mass or volume of each chemical reagents used should be stated, as per the pre-experiment calculations done beforehand.
5. Experimental Results
This is also almost confirmed that you will be tested in every Planning question.
You are expected to be able to construct appropriate tables with headings, in order to record experimental data.
6. Treatment of Results
This is also almost confirmed that you will be tested in every Planning question.
You are required to use relevant formulae to perform calculations.
You will also likely be asked to plot relevant graphs and use it to solve follow up question.
Preferably, you should use a hypothetical experimental result (e.g. x cm3) and show how it can be used to achieve the aim of the experiment.
7. Safety considerations
You will need to identify one or more safety risks and suggest ways to overcome the safety risks.
8. Reliability of Results
You should also state and explain measures taken to ensure reliability of the experimental results.
B) Possible Planning Questions for 2019 H2 Chemistry Practical Exam (Paper 4):
The following are possible Planning questions which you may be asked in the upcoming GCE A-Level H2 Chemistry Practical Exam (Paper 4):
1. Titrations or Volumetric Analysis Experiments
Acid-base and redox titrations are the most common. The apparatus involved are usually: pipette, burette, conical flask, volumetric flask (to make the standard solution or for carrying out dilution) and an indicator (optional).
Possible Planning Questions on Titrations or Volumetric Analysis Experiments:
- Determine the % by mass of KHCO3 in a mixture of KHCO3 and KCl
- Determine the % by mass of KHCO3 in a mixture of KHCO3 and KOH
- Determine the % by mass of CaCO3 in a sample of Impure Limestone
- Determine the Relative Atomic Mass of Na metal using Back Titration
- Determine the Relative Formula Mass of a Carbonate using Back Titration
- Determine the Percentage Purity of Na2CO3 using Back Titration
- Determine the Identity of an Acid
- Determine how the Presence of CO2 affects the Solubility of BaCO3 using Acid-Base Titration
- Determine the Equilibrium Constant, Kc for the Formation of an Ester
- Determine the Acid Dissociation Constant, Ka of CH3COOH
- Determine the Value of n in (COOH)2.nH2O using Acid-Base Titration
- Determine the Value of n in (COOH)2.nH2O using Redox Titration
- Determine the Value of n in CuSO4.nH2O using Redox Titration
- Determine the Solubility Product Constant, Ksp for Ba(IO3)2 using Redox Titration
2. Gravimetric Analysis Experiments
This analytical method requires you to determine the quantity of an analyte through the measurement of mass of solid which could be the residue left after a thermal decomposition reaction or a precipitate that is formed from mixing aqueous solutions.
Possible Planning Questions on Gravimetric Analysis Experiments:
- Determine the % by mass of KHCO3 in a mixture of KHCO3 and KCl
- Determine the % by mass of PbCO3 in a mixture of PbCO3 and BaCO3
- Determine the % of Na2S2O3 in an Impure Sample of Na2S2O3
- Determine the Concentration of HCl using AgNO3 solution
3. Gas Collection Experiments
The amount of an analyte can be determined by measuring the volume of the gas evolved when an excess of a reagent is added to the analyte. This method is suitable for any chemical reactions that give off a gaseous product.
The gas evolved can be collected using either a graduated gas syringe directly or through water displacement, using a measuring cylinder.
Possible Planning Questions on Gas Collection Experiments:
- Determine the % by mass of KHCO3 in a mixture of KHCO3 and KCl
- Determine the % by mass of CaCO3 in a sample of Impure Limestone
- Determine the Ideal Gas Constant, R by reacting BaCO3 with HCl
- Determine the Identity of an Acid
- Determine the Value of n in (COOH)2.nH2O using Gas Collection
- Determine the Decomposition Equation of KNO3 using Gas Collection
- Determine the Concentration of H2O2 using Gas Collection
4. Chemical Energetics Experiments
Energy changes usually occur in a chemical reaction. If the energy changes is in the form of heat, we can measure it by simply measuring the temperature change using a thermometer since heat is directly proportional to temperature.
The thermochemical experiment set-up would require a thermometer to register the temperature change in the shortest time with minimal heat loss to the surroundings. The following equation to determine the heat change is involved: q = mc∆T.
Possible Planning Questions on Chemical Energetics Experiments:
- Determine the Enthalpy Change of Solution of NaCl
- Determine the Enthalpy Changes of Reaction between Na2CO3 and HCl
- Determine the Enthalpy Changes of Reaction between Zn and CuSO4
- Determine the Enthalpy Changes of Reaction between MgO(s) and HCl by Plotting a Graph
- Determine the Enthalpy Changes of Neutralisation between Ba(OH)2 and HNO3
- Determine the Identity of an Acid using Thermometric Titration
- Determine the Concentration of an Acid using Thermometric Titration
- Determine the Purity of a Solid Sample of MgO using Thermometric Titration
- Determine the Strength (Strong or Weak) of an Acid
- Determine the Enthalpy Changes of Combustion of an Organic Compound
- Determine the Heat Capacity of a Calorimeter
- Determine the Enthalpy Changes of Combustion of an Organic Compound by taking into consideration the Heat Absorbed by the Calorimeter
5. Reaction Kinetics Experiments
Reaction Kinetics refers to the study of the rate of a chemical reaction. In the Chemistry laboratory, rate of reaction = (change in concentration of a reactant or product) / (change in time).
As such, the rate of reaction can be determined by two ways:
- Initial Rate Method – measure the time taken for a particular concentration change
- Continuous Method – monitor the concentration of a species continuously with respect to time. Gradient of the plot of concentration [ ] versus time will give us the rate.
Order of reaction with respect to each reactant can also be determined.
Possible Planning Questions on Reaction Kinetics Experiments:
- Determine the Rate of Reaction between HCl and CaCO3 by monitoring the mass of system
- Determine the Rate of Decomposition of H2O2 by collecting O2(g) evolved
- Determine the Rate of Decomposition of H2O2 by titrating with KMnO4(aq)
- Determine the Order of Reaction of Na2S2O8 and KI using the Initial Rate Method
- Determine the Order of Reaction of H2O2 and KI using the Initial Rate Method
- Determine How the Concentration of an Acid Affects the Rate of Reaction of Magnesium
- Determine the Order of Reaction of Iodination of Propanone using Calorimetry
6. Electrochemistry Experiments
There are two types of cells in Electrochemistry.
An electrochemical cell (also known as electric or voltaic cell) is one which converts chemical energy to electrical energy via spontaneous redox reactions.
An electrolytic cell is one which undergoes non-spontaneous redox reactions known as electrolysis, when an electric current is passed through the electrolyte.
Possible Planning Questions on Electrochemistry Experiments:
- Determine the Cell Potential of an Electrochemical Cell
- Determine the Effect of Concentration on the Cell Potential
- Determine the Charge of an Ion through Electrolysis
- Determine the Avogadro’s Number through Electrolysis
- Design an Experiment for Purification of Copper
- Design an Experiment for Electroplating
7. Inorganic Qualitative Analysis Experiments
This involves the identification of cations, anions and gases through the use of common chemical reagents in the laboratory. Such analysis is commonly being done in the other parts of the Chemistry Practical but may also come out in Planning questions. Please refer to previous blogpost on Tips for GCE A Level H2 Chemistry Practical Exam 2019.
Possible Planning Questions on Inorganic Qualitative Analysis Experiments:
- Testing of Cations using NaOH(aq) or NH3(aq)
- Testing of Anions using Common Chemical Reagents (listed in the Data Booklet)
- Testing of Gases
- Qualitative Analysis with an External Reagent (not listed in the Data Booklet)
- Qualitative Analysis with the use of an Unknown Solution as Testing Reagent
- Separation of Ions using Precipitation Method
8. Organic Qualitative Analysis Experiments
This involves the testing of specific functional groups in the organic compounds that result in characteristic chemical reactions and leads to observable changes.
- Test for Alkenes
- Test for Alkylbenzene
- Test for Halogenoalkane
- Test for Alcohol
- Test for Phenol
- Test for Aldehyde
- Test for Ketone
- Test for Carboxylic Acids
- Test for Acid Halides
- Test for Esters
- Test for Amides
- Test for Amines
- Test for Phenylamines
- Test for Nitriles
- Test for Ammonium Salts
9. Organic Synthesis Experiments
Organic compounds can be synthesised from simple molecules via organic reactions which could be single step or multiple steps. For most organic synthesis, it is very unlikely we have 100% yield. There will always be side products which are formed. As such, separation and purification techniques are very important in organic synthesis.
If we have two miscible liquids, they can be separated by the use of fractional distillation.
If we have two immiscible liquids, they can be separated by the use of separating funnel.
If we have a solid and a liquid mixture, filtration can be used to separate them.
Chromatography is also commonly used to separate organic compounds.
Sublimation and recrystallization are techniques commonly used to purify the organic compounds obtained.
Purity of the organic compounds is usually determined by the melting point test.
Possible Planning Questions on Organic Synthesis Experiments:
- Preparation of Pure Aspirin (an Ester)
10. Spectrophotometric Analysis Experiments
Possible Planning Questions on Spectrophotometric Analysis Experiments:
- Determine the Concentration of [Ni(H2O)6]2+ in an Unknown Solution
- Determine the Concentration of Copper(II) ions in an Unknown Solution
- Determine the Formula of the [Ni(NH3)n]2+ Complex
I hope you find the above sharing on Tips for Planning Questions in GCE A-Level H2 Chemistry Practical Exam (Paper 4) useful. All the best for your practical exam!
For GCE A-Level H2 Chemistry Examination (code: 9729), there will still be Paper 2 (Structured Questions) with 30% weightage, Paper 3 (Free Response Questions) with 35% weightage and Paper 1 (MCQ Paper) with 15% weightage after Paper 4 (Practical Paper). As such, it is important that students continue to revise their theories and concepts all the way until the last paper.
A quick note that we will be conducting our annual Score 100% A-Level H2 Chemistry MCQ Workshop on 22 & 23 Nov 2019 to help students to score full marks for their Paper 1 (MCQ Paper) with 15% weightage. We have consistently received positive feedbacks and glowing reviews for this annual workshop and this will be the 7th consecutive year that we are conducting it. WhatsApp us at 88290998 for more details if you are committed to UP your overall H2 Chemistry grade.
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