IB Chemistry HL Paper 3 Question Bank

SECTION A

1.) Powdered zinc was reacted with 25 cm3 of 1.000 mol/dm³ copper (II) solution in an insulated beaker. The graph below shows the temperature plotted against time

a.) Estimate the time when powdered zinc was placed in the beaker using the graph above
Answer
100 seconds because that’s the data point when the graph begins to increase and slope. It shows that a reaction is occurring.
b.) State what Y indicates in the graph
Answer
Y is the maximum temperature attained in the reaction. According to the graph, the temperature is 73 degree celsius.
c.) The experiment was carried out multiple times to determine the enthalpy. The volume and concentration of copper(II) sulfate was kept constant but the mass of zinc was varied during each trial. Suggest if zinc or copper(II) sulfate should be in excess for each trial.
Answer
Since the amount of copper (II) sulfate is constant and zinc is in excess, it will not yield different results in each trial.

2.) Bromine and methanoic acid react in an aqueous solution. The equation is shown below:
Br2 (aq) + HCOOH (aq) → 2Br- (aq) + 2H+ (aq) + Br2 (g)
The reaction was monitored by plotting a graph of the volume of carbon dioxide produced against time.

a.) Determine the rate of reaction at 20 seconds using the graph
Answer
A tangent line is drawn at 20 seconds and the gradient of the line is determined. The slope of the line is 0.35 cm3/s

b.) Suggest another variable that can be measured to determine the rate of reaction
Answer
Pressure or mass of gas since gas is produced in the reaction. An alternative is the color of the solution since Bromine (reactant) is coloured. However, the Bromine ion is not.

c.) There are random errors and systematic errors.
i.) One such systematic error is associated with the use of the gas syringe. Outline what this error is and how it affects the calculated rate of reaction.
Answer
Gas could leak out of the syringe so the rate of reaction calculated would essentially be lower.

ii.) State one error that could possibly occur from using an accurate stopwatch
Answer
However accurate the stopwatch is, human reaction time will always be accounted as human error.

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SECTION B – Option A Materials

1.) Lithium metal is obtained by electrolysis of molten lithium chloride.

a.) Calculate the time it takes to deposit 0.842 g of lithium using a current of 3.31 A. Formula is Q (Charge) = I (Current) x T (Time)
Answer
Number of moles = m / mr = 0.842/6.94 = 0.121 moles
Time = Charge / Current = (96500 x 0.121) / 3.31 = 3527.64 seconds → 3530 s

b.) When lithium is doped into graphene, it is seen to have some superconductive properties. However, the Meissner effect is absent. Describe the Meissner effect.
Answer
The expulsion of a magnetic field from the interior of a material that is in the process of becoming a superconductor.

c.) Lithium atoms enhance the phonon binding of electrons in graphene at very low temperatures. This in turn suggests the formation of Cooper Pairs. Outline how they are formed.
Answer
Cooper pairs are formed by electron-phonon interactions – an electron in the cation lattice will distort the lattice around it, creating an area of greater positive charge density around itself.
d.) Lithium forms a crystalline lattice with the unit cell structure shown below. Describe the characteristics of a crystalline lattice structure
Answer
The crystal lattice is the symmetrical three-dimensional structural arrangements of atoms, ions or molecules inside a crystalline solid as points.

2.) Nanotechnology has allowed the manipulation of materials on the atomic level

a.) Describe the structure and bonding of a carbon nanotube
Answer
The chemical bonding of CNTs is composed entirely of sp2 bonds, similar to those of graphite and are arranged in a hexagonal pattern. CNTs naturally align themselves into ropes held together by van der Waals forces.
b.) Suggest one place where carbon nanotubes are used
Answer
They are used to make bullet-proof jackets, aircraft and spacecraft bodies.
c.) Liquid crystals have many applications. A molecule which acts as a chiral nematic thermotropic liquid-crystal is given.

i.) Define thermotropic liquid crystals
Answer
They are anisotropic liquids that possess a mesophase (a phase with crystal and liquid properties) within a certain temperature range. In a spectrometer magnet, LC molecules tend to orient to a common direction which defines the director of the liquid crystal.

ii.) Mark the chiral carbon atom with a cross
Answer

3.) Superconductors has a variety of applications

a.) Define superconductors
Answer
Superconductors are solids that at low temperatures exhibit zero resistance to the flow of electrical current
b.) Differentiate between Type 1 and Type 2 superconductors
Answer
Type-I superconductors are generally pure metals. Type-II superconductors are generally alloys and complex oxides of ceramics. Type I superconductors are those superconductors that lose their superconductivity very easily or abruptly when placed in the external magnetic field whereas Type II superconductors lose their superconductivity gradually but not easily or abruptly when placed in the external magnetic field.
c.) Give two examples of a superconductor
Answer
Some examples of superconductors are aluminum, copper oxide, etc. These substances superconduct at temperatures below the critical temperature.

4.) Heavy metals are known to be toxic even in the lowest of the concentrations

a.) Suggest a reason why heavy metals are toxic
Answer
Heavy metals are toxic because the molecules that make up the metal damage or negatively interact with the cells in your body that are essential to keep your organs functioning.
b.) Outline how heavy metals can be removed from solutions other than precipitation
Answer
Chelation using an EDTA, ion exchange systems, or adsorption by water plants
c.) Chelating agents are used to treat heavy metal poisoning.
1.) State one feature of a chelating agent
Answer
Chelating agents are capable of binding to toxic metal ions to form complex structures which are easily excreted from the body removing them from intracellular spaces.

5.) This question is about polymers

a.) Define thermoplastic polymers and thermosetting polymers
Answer
Thermoplastic polymers are a form of plastic polymers that are moldable at a certain high temperature and solidify when cooled. Thermosetting polymers are polymers consisting of cross-linked structure or heavily branched molecules. It is a permanent setting polymer as it hardens and sets during the molding process and cannot be softened again.
b.) Cyclohexane can be converted to caprolactam using concentrated sulfuric acid as a catalyst. Zeolite can also be used as a catalyst in this reaction, however, they are selective. Suggest why they are selective catalysts.
Answer
Zeolites have cage-like structures in a specific shape and size. Only reactants with an appropriate size will be able to fit inside and react.

c.) Caprolactam reacts with water to form a compound X, a monomer.