ChemistryAssessment Objectives

1. Demonstrate knowledge and understanding of:• facts, concepts and terminology• methodologies and techniques• communicating scientific information.

2. Apply:• facts, concepts and terminology• methodologies and techniques• methods of communicating scientific information.

3. Formulate, analyse and evaluate:• hypotheses, research questions and predictions• methodologies and techniques• primary and secondary data• scientific explanations.

4. Demonstrate the appropriate research, experimental, and personal skills necessary to carry out insightful and ethical investigations.

SL Assessment OutlineAssessment component WeightingPaper 1 20%Paper 2 40%Paper 3 20%Internal Assessment 20%

HL Assessment outline

Assessment component WeightingPaper 1 20%Paper 2 36%

Paper 3 24%Internal Assessment 20%

SL External Assessment details

Paper 1Duration: 3/4 hour • 30 multiple-choice questions on core, about 15 of which are common

with HL.• The questions on paper 1 test assessment objectives 1, 2 and 3.• The use of calculators is not permitted.• Students will be provided with a periodic table.• No marks are deducted for incorrect answers.

Example exam questions.Chemistry Standard Level Paper 1.

Which graph shows the Maxwell-Boltzmann energy distribution of a same amount of a gas at two temperatures, where T2 is greater than T1?

The equations below represent reactions involved in the Winkler method for determining the concentration of dissolved oxygen in water:

What is the amount, in mol, of thiosulfate ions, needed to react

with the iodine, I2(aq), formed by 1.00 mol of dissolved oxygen?A. 2.00B. 3.00C. 4.00D. 6.00

Which is propyl propanoate?

A. CH3CH2CH2OOCCH2CH3B. CH3CH2CH2COOCH2CH3C. CH3CH2CH2COCH2CH3D. CH3CH2CH2OCH2CH2CH3

Paper 2Duration: 1¼ hours • Short-answer and extended-response questions on core material.• The questions on paper 2 test assessment objectives 1, 2 and 3.• The use of calculators is permitted. (See calculator section on the OCC.)• A chemistry data booklet is to be provided by the school.

Example exam questions.Chemistry Standard Level Paper 2.

The biopharmaceutical industry is now a global contributor to the world economy.

(a) Atorvastatin, a drug used to lower cholesterol, recently gained attention from the global media.

Atorvastatin has the structure shown below.

(b) Bute, a painkiller used on horses, has caused widespread concern recently because

analytical tests showed that it entered the food chain through horse meat labelled as beef.

The drug is suspected of causing cancer.(i) Analysis of a sample of bute carried out in a food safety laboratory gave the

following elemental percentage compositions by mass:

(ii) The molar mass, M, of bute, is 308.37 g mol–1. Calculate the molecular formula. (1)

(iii) Deduce the degree of unsaturation (index of hydrogen deficiency – IHD) of bute. (1)

(iv) The infrared (IR) spectrum of bute is shown below.

Using information from section 26 of the data booklet, identify the bonds

corresponding to A and B. (1)A:B:

(v) Based on analysis of the IR spectrum, predict, with an explanation, one bond

containing oxygen and one bond containing nitrogen that could not be present in

the structure. (2)Bond containing oxygen not present in structure:Bond containing nitrogen not present in structure:

Explanation:

(c) An alcohol, X, of molecular formula C3H8O, used as a disinfectant in hospitals, has the following 1H NMR spectrum.

The three peaks in the 1H NMR spectrum of X have chemical shift values centred at δ = 4.0, 2.3 and 1.2 ppm.

(i) From the integration trace, estimate the ratio of hydrogen atoms in different

chemical environments. (1)

(ii) Deduce the full structural formula of X.

(iii) Y is an isomer of X containing a different functional group. State the condensed structural formula of Y.

(iv) Compare and contrast the expected mass spectra of X and Y using section 28 of the data booklet. (2)

One similarity:One difference:

(v) Both X and Y are soluble in water. Deduce whether or not both X and Y show

hydrogen bonding with water molecules, representing any hydrogen

bondingpresent by means of a diagram. (2)

(vi) X reacts with acidified potassium dichromate(VI) solution to form Q and with

ethanoic acid to form W. Deduce the condensed structural formula of Q and W. (2)

Q:

W:

(vii) Apply IUPAC rules to state the name of compound Q. (1)

Paper 3Duration: 1 hour• This paper will have questions on core and SL option material.• Section A: one data-based question and several short-answer questions

on experimental work.• Section B: short-answer and extended-response questions from one

option.• The questions on paper 3 test assessment objectives 1, 2 and 3.• The use of calculators is permitted. (See calculator section on the OCC.)• A chemistry data booklet is to be provided by the school.

Example exam question.Chemistry Standard Level Paper 3.

Section A

(a) (i) Explain why the values for ODP and GWP have no units. (1)(ii) By making reference to the chemical formulas and ODP values of the compounds, comment on the hypothesis that chlorine is responsible for ozone depletion. (1)(b) Use data from the table to interpret the relationship between the atmospheric lifetime of a gas and its GWP. (2)

Section B

HL Assessment Overview

HL Paper 1Duration: 1 hourWeighting: • 40 multiple-choice questions on core and AHL, about 15 of which are

common with SL.• The questions on paper 1 test assessment objectives 1, 2 and 3.• The use of calculators is not permitted.• Students will be provided with a periodic table.• No marks are deducted for incorrect answers.

Example exam question.Chemistry Higher Level Paper 1.

Which electronic transition would absorb the radiation of the shortest wavelength?

Which is the electron configuration of the ion Fe2+?A. 1s2 2s2 2p6 3s2 3p6 3d6B. 1s2 2s2 2p6 3s2 3p6 3d6 4s2C. 1s2 2s2 2p6 3s2 3p6 3d4 4s2D. 1s2 2s2 2p6 3s2 3p6 3d5 4s1

When 0.46 g of ethanol is burned under a water-filled calorimeter, the temperature of 500 g of water is raised by 3.0 K. (Molar mass of ethanol = 46 g mol–1; specific heat capacity of water = 4.18 J g–1 K–1; q = mcΔT.)

What is the expression for the enthalpy of combustion, ΔHc, in kJ mol–1?

HL Paper 2Duration: 2¼ hours• Short-answer and extended-response questions on the core and AHL

material.• The questions on paper 2 test assessment objectives 1, 2 and 3.• The use of calculators is permitted. (See calculator section on the OCC.)• A chemistry data booklet is to be provided by the school.

Example exam question.Chemistry Higher Level Paper 2.

1. Two IB students carried out a project on the chemistry of bleach.

(a) The bleach contained a solution of sodium hypochlorite, NaClO (aq). The students determined experimentally the concentration of hypochlorite ions, ClO–, in the bleach:

Experimental procedure:• The bleach solution was first diluted by adding 25.00 cm3 of the bleach to a 250 cm3 volumetric flask. The solution was filled to the graduation mark with deionized water.• 25.00 cm3 of this solution was then reacted with excess iodide in acid.

• The iodine formed was titrated with 0.100 mol dm–3 sodium thiosulfate solution,Na2S2O3(aq), using starch indicator.

The following data were recorded for the titration:

(i) Calculate the volume, in cm3, of 0.100 mol dm–3 Na2S2O3(aq) required to react with the iodine to reach the end point. (1)

(ii) Calculate the amount, in mol, of Na2S2O3(aq) that reacts with the iodine. (1)

(iii) Calculate the concentration, in mol dm–3, of hypochlorite ions in the dilutedbleach solution. (1)

(iv) Calculate the concentration, in mol dm–3, of hypochlorite ions in the undiluted bleach solution. (1)

(b) Some of the group 17 elements, the halogens, show variable valency.

(i) Deduce the oxidation states of chlorine and iodine in the following species. (1)

(ii) Deduce, with a reason, the oxidizing agent in the reaction of hypochlorite ions with iodide ions in part (a). (1)

(iii) From a health and safety perspective, suggest why it is not a good idea to usehydrochloric acid when acidifying the bleach. (1)

(iv) The thiosulfate ion, is an interesting example of oxidation

states.The sulfur atoms can be considered to have an oxidation state of

+6 on one atom and –2 on the other atom. Discuss this statement in terms of your understanding of oxidation state. (2)

(c) The various changes that have been made to the definitions of oxidation and reduction show how scientists often broaden similarities to general principles.

Combustion is also a redox type of reaction.With reference to the combustion reaction of methane, explore two different definitions of oxidation, choosing one which is valid and one which may be considered not valid. (2)

Valid…

Not valid….

(d) (i) State the condensed electron configuration of sulfur.

(ii) Deduce the orbital diagram of sulfur, showing all the orbitals present in the diagram.

HL Paper 3Duration: 1¼ hours • This paper will have questions on core, AHL and option material.• Section A: one data-based question and several short-answer questions

on experimental work.• Section B: short-answer and extended-response questions from one

option.• The questions on paper 3 test assessment objectives 1, 2 and 3.• The use of calculators is permitted. (See calculator section on the OCC.)• A chemistry data booklet is to be provided by the school.

Example exam question.Chemistry Higher Level Paper 3.

1 Compounds used to generate cooling in refrigerators and air-conditioning systems are known as refrigerants. A refrigerant undergoes a reversible change of state involving vaporization and condensation. The search for suitable refrigerants has occupied chemists for approximately 200 years.Previously, the most popular refrigerants were chlorofluorocarbons (CFCs), but these have been replaced first by hydrochlorofluorocarbons (HCFCs) and more recently by hydrofluorocarbons (HFCs).

Some data on examples of these three classes of refrigerants are shown

below.

(a) (i) Explain why the values for ODP and GWP have no units. (1)

(ii) By making reference to the chemical formulas and ODP values of the compounds,comment on the hypothesis that chlorine is responsible for ozone depletion.

(b) Use data from the table to interpret the relationship between the atmospheric lifetime of a gas and its GWP.

(c) The graph shows the change in levels with time of equal masses of CO2 and CH2FCF3 introduced into the atmosphere.

(iii) With reference to the graph on page 4, comment on the atmospheric lifetime of

CO2 relative to CH2FCF3, and on the likely influence of this on climate change. (2)

2 DNA is the molecule that carries genetic information in nearly all cells. Two months before Watson and Crick published their paper describing the double helical nature of DNA in 1953, Linus Pauling published a suggested structure for DNA based on a triple helix. Pauling’s model, which was soon proved to be incorrect, had the phosphate groups facing into the core of the helix and the nitrogenous bases facing out.

(a) Suggest why Pauling’s model would not have been a stable structure for DNA. (2)

(b) DNA has the unusual property of being able to replicate. State the type and position of the bonds that break at the start of the replication process.

Command terms for Assessment Objective 1: Demonstrate Knowledge and Understanding.

Command Term DefinitionClassify Arrange or order by class or category.Define Give the precise meaning of a word, phrase, concept

or physical quantity.Draw Represent by means of a labelled, accurate diagram

or graph, using a pencil. A ruler (straight edge) should be used for straight lines. Diagrams should be drawn to scale. Graphs should have points correctly plotted (if appropriate) and joined in a straight line or smooth curve.

Label Add labels to a diagram.List Give a sequence of brief answers with no explanation.Measure Obtain a value for a quantity.State Give a specific name, value or other brief answer

without explanation or calculation.

Command terms for Assessment Objective 2: Apply

Command Term DefinitionAnnotate Add brief notes to a diagram or graph.Apply Use an idea, equation, principle, theory or law in

relation to a given problem or issue.Calculate Obtain a numerical answer showing the relevant

stages in the working (unless instructed not to do so).Describe Give a detailed account.Distinguish Make clear the differences between two or more

concepts or items.Estimate Obtain an approximate value.Formulate Express precisely and systematically the relevant

concept(s) or argument(s).Identify Provide an answer from a number of possibilities.

Outline Give a brief account or summary.

Command terms for Assessment Objective 3: Formulate, analyse and evaluate:

Command Term DefinitionAnalyse Break down in order to bring out the essential

elements or structure.Comment Give a judgment based on a given statement or result

of a calculation.Compare Give an account of the similarities between two (or

more) items or situations, referring to both (all) of them throughout.

Compare and contrast

Give an account of the similarities between two (or more) items or situations, referring to both (all) of them throughout.

Deduce Reach a conclusion from the information given.Demonstrate Make clear by reasoning or evidence, illustrating with

examples or practical application.Derive Manipulate a mathematical relationship to give a new

equation or relationship.Design Produce a plan, simulation or model.Determine Obtain the only possible answer.Discuss Offer a considered and balanced review that includes

a range of arguments, factors or hypotheses. Opinions or conclusions should be presented clearly and supported by appropriate evidence.

Evaluate Make an appraisal by weighing up the strengths and limitations.

Examine Consider an argument or concept in a way that uncovers the assumptions and interrelationships of the issue.

Explain Give a detailed account including reasons or causes.Explore Undertake a systematic process of discovery.

Interpret Use knowledge and understanding to recognize trends and draw conclusions from given information.

Justify Give valid reasons or evidence to support an answer or conclusion.

Predict Give an expected result.Show Give the steps in a calculation or derivation.Sketch Represent by means of a diagram or graph (labelled

as appropriate). The sketch should give a general idea of the required shape or relationship, and should include relevant features.

Solve Obtain the answer(s) using algebraic and/or numerical and/or graphical methods.

Suggest Propose a solution, hypothesis or other possible answer.