OCR A Level Chemistry B (Salters) Fundamentals of chemistry June 2023 question paper H433/01

Helium-4 is formed by a nuclear fusion reaction.

What is needed to complete the equation?

A 1 electron

B 1 neutron

C 1 proton

D 2 protons

Which molecule is the most polar?

A CCl₄

B CF₄

C CHF₃

D CHCl₂F

One of the principles of green chemistry in industrial processes involves the use of a selective catalyst.

Which of the following makes a selective catalyst ‘green’?

A It speeds up the process.

B It improves the atom economy.

C It minimises the use of organic solvents.

D It reduces energy usage and minimises waste product.

Sodium phosphate(V) has the formula Na₃PO₄.

What is the formula of calcium phosphate(V)?

A CaPO₄

B Ca₂(PO₄)₃

C Ca₃PO₄

D Ca₃(PO₄)₂

A colorimeter is used to measure the concentration of a blue solution of copper(II) sulfate(VI).

Which of the following is correct?

A A blue filter is used.

A calibration curve is plotted with known concentrations of Cu²⁺. B

The amount of light transmitted is proportional to the Cu²⁺ concentration. C

The measured absorbance decreases with increasing Cu²⁺ concentration. D

A student studies a reaction that ‘goes to completion’.

The student estimates the numerical value of K_c for the reaction.

What is a valid estimate for K_c for this reaction?

A 0

1 × 10^–10 B

C 1

1 × 10¹⁰ D

Which of the following is correct for gas-liquid chromatography?

A A reactive carrier gas is used.

B The column consists of a volatile liquid on a porous support.

C The emerging compounds can be detected by mass spectrometry.

D The largest molecules usually have the shortest retention times.

Which of the following molecules is linear?

A HCN

B H₂S

C NO₂

D SO₂

Sodium nitrate(V) is warmed with Devarda’s alloy and NaOH(aq).

Which gas is released?

A ammonia

B nitrogen

C nitrogen dioxide

D nitrogen monoxide

Which row shows the number of sigma () and pi () bonds in one molecule of buta-1,3-diene, CH₂=CHCH=CH₂?

	Sigma () bonds	Pi () bonds
A	7	2
B	7	4
C	9	2
D	9	4

Which combination of organic molecules can be formed during the cracking of octane?

A propane + pentane

B propene + pentane

C propene + pent-1-ene

D 2 molecules of butane

Which of the following compounds can display E / Z isomerism?

A CH₂BrCH=CHCH₂Br

B (CH₃CH₂)₂C=CBr₂

C (CH₂Br)₂C=CH₂

D CH₂BrCH₂BrCH=CH₂

Which row is possible for a transition metal complex?

What is the correct order of boiling points for CH₃CH₂OH, CH₃CHO and CH₃COOH?

A CH₃CHO > CH₃CH₂OH > CH₃COOH

B CH₃COOH > CH₃CH₂OH > CH₃CHO

C CH₃CH₂OH > CH₃COOH > CH₃CHO

D CH₃CH₂OH > CH₃CHO > CH₃COOH

Which compound can undergo an elimination reaction to produce an alkene?

A (CH₃)₃CH

B C₆H₅OH

C C₆H₅CH₂OH

D CH₃CH(CH₃)CH₂OH

10 cm³ of pentane gas is burned in 100 cm³ of oxygen at constant pressure and 390 K. 18

What volume of gas is present when all the pentane has burned under these conditions?

50 cm³ A

110 cm³ B

130 cm³ C

138 cm³ D

Which statement is correct for the Group 1 chlorides, going down the group?

A The charge density of the anion becomes smaller.

B The charge density of the cation becomes greater.

C The hydration energy of the cation becomes less exothermic.

D The lattice enthalpy becomes more exothermic.

The following equations represent reactions for making hydrogen from water.

Which reaction produces hydrogen with the greatest atom economy?

A student plots a graph of ln k (y-axis) against 1/ T for a reaction. The student draws the straight line of best fit.

The Arrhenius equation is ln k = –E_a/RT + ln A

Which statement is correct?

A The graph shows that ln k is proportional to T.

B The intercept of the line on the y-axis is ln A.

C The slope of the line is E_a/RT.

D When T = 0, ln k = ln A.

What is correct about the structure of DNA?

A Guanine is paired with Adenine.

B The repeating units in the backbone are deoxyribose-phosphate-deoxyribose-phosphate.

C The bases are joined by condensation to phosphate groups.

D The bases involved are represented as A C G and U.

The data below is for the dissolving of MgCl₂ in water.

What is the enthalpy change of solution of MgCl₂ in kJ mol^–1?

A –222

B –156

C +156

D +222

A student records the following readings for a titration:

What should the student record as the result of the titration?

20.10 cm³ A

20.17 cm³ B

20.19 cm³ C

20.28 cm³ D

What is the amount (in moles) of a gas that occupies 23 dm³ at 1.0 × 10⁵ Pa and 293 K? 26

A 0.94 mol

B 1.4 mol

C 14 mol

D 94 mol

Which of these would cause an increased greenhouse effect?

1 an increased concentration of CO₂ in the troposphere

2 less UV from the Sun reaching the Earth

3 the Earth radiating less IR

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Which statement(s) is/are correct for a Friedel-Crafts alkylation reaction?

1 An alkyl group bonds with a benzene ring by an addition reaction.

2 Al Cl₃ is used as a catalyst.

3 A chloroalkane forms a carbocation during the reaction.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Iodine is soluble in hexane.

Which of the following is/are reason(s) that it dissolves?

1 Instantaneous dipole – induced dipole bonds of similar strength are broken and made.

2 The I – I covalent bond is weak.

3 Iodine and hexane both have permanent dipole – permanent dipole bonds.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

This question is about Group 2 elements and their compounds.

Strontium is one of the elements in Group 2. Compounds of strontium are used in fireworks to give a crimson colour.

Analysis of the mass spectrum of a sample of strontium gives the data shown below.

Use this data to calculate the relative atomic mass, A_r, of this sample of strontium.

Give your answer to 2 decimal places.

The atomic emission spectrum of strontium shows a series of coloured lines against a black background.

The diagram shows the line of shortest frequency in the spectrum and the electron energy change causing it.

Complete the diagram to show the relationship between the next two lines in the spectrum and the corresponding energy changes.

atomic emission spectrum:

A student has three test tubes, each containing the same volume and concentration of a different solution.

• One test tube contains aqueous calcium nitrate.

• One test tube contains aqueous strontium nitrate.

• One test tube contains aqueous barium nitrate.

The student adds an equal volume of aqueous sodium hydroxide to each test tube. A white precipitate forms rapidly in the test tube containing calcium nitrate.

Describe and explain the trend in what the student would observe in the other two test tubes.

Another student uses a roaring Bunsen flame to heat a small sample of calcium carbonate in a test tube. The gas given off is bubbled through lime water.

After about 1 minute the lime water is white and cloudy.

Write an equation for the reaction that occurs when the calcium carbonate is heated.

Include state symbols.

Carbonates of metals below calcium in Group 2 are heated under the same conditions. The lime water becomes cloudy after different amounts of time.

Describe and explain the trend in thermal stabilities of the Group 2 carbonates.

Barium chloride solution is used as a test for the sulfate ion.

Write an ionic equation for the reaction that occurs when this test is done.

Include state symbols.

The impact of climate change is driving the development of replacements for fossil fuels. Crude oil currently remains a source of hydrocarbons, some of which can be used as fuels.

Octane, C₈H₁₈, is one of the alkane hydrocarbons present in petrol.

For maximum fuel efficiency, petrol should burn completely. However, some incomplete combustion usually takes place.

Write an equation for the incomplete combustion of octane that forms carbon monoxide as the only carbon compound.

2,2,3-trimethylpentane is a structural isomer of octane.

Draw the skeletal formula for 2,2,3-trimethylpentane.

Ethanol is often added to petrol to improve combustion.

A student wishes to measure the enthalpy change of combustion of ethanol.

The student carries out a simple method.

Step 1 Some water is measured into a copper can. Step 2 The initial temperature of the water in the can is measured. Step 3 The initial mass of a spirit burner containing ethanol is measured. Step 4 The spirit burner is placed under the can which is held above it using a clamp. Step 5 The wick of the spirit burner is lit. Step 6 After heating the water in the can, the flame is blown out. Step 7 The final temperature of the water is measured. Step 8 The final mass of the spirit burner is measured.

The results are recorded in Table 32.1.

Table 32.1

A value for the enthalpy change of combustion of ethanol can also be calculated using the average bond enthalpy values given in Table 32.2.

Table 32.2

Why are the bond enthalpies in Table 32.2 described as average values?

The larger bond enthalpy of C=O compared with C–O implies that the C=O bond is shorter.

Explain why double bonds are shorter than single bonds between the same atoms.

The ethanol that is mixed with fossil fuels in petrol can be made by fermentation of crops.

A student says that this ethanol is carbon neutral in petrol.

Discuss this statement.

Citric acid is a weak acid that is present in many fruits. The addition of citrate salts to fruit-based products such as jams forms buffer solutions in the products.

A student uses citric acid, C₃H₅O(COOH)₃, to prepare a sample of sodium citrate, C₃H₅O(COONa)₃ as shown in Equation 33.1.

C₃H₅O(COOH)₃ + 3NaOH C₃H₅O(COONa)₃ + 3H₂O Equation 33.1

The M_r of citric acid is 192.

The student uses 4.80 g of citric acid and obtains 5.18 g of sodium citrate.

Calculate the percentage yield in this salt preparation.

The pH of the sodium hydroxide solution used in this salt preparation is 13.46 at 25 °C.

Calculate the concentration of the sodium hydroxide solution.

concentration of sodium hydroxide =........ mol dm^–3

Buffer solutions are also important in living systems. For example, human blood needs to be maintained at a pH between 7.35 and 7.45.

The buffering action in blood involves the equilibrium as represented by Equation 33.2.

Identify the Brønsted-Lowry acid and conjugate base in Equation 33.2.

Brønsted-Lowry acid........

Conjugate base........

Using Equation 33.2, explain how this buffer solution maintains its pH when small amounts of acid and alkali are added.

A student sets up an electrochemical cell in the laboratory based on redox half-cells 1 and 6

Complete the labelled diagram to show the student’s cell.

State the types of particle that cause the transfer of charge through the wire and the solutions.

The wire........

The solutions........

Standard electrode potentials can be used to explain how some metals protect iron from rusting.

A thin coating of zinc on the surface of iron will provide protection from rusting even when the zinc coating becomes scratched. However, a scratched thin coating of tin will not protect the surface.

Use the data in Table 34.1 to explain these observations.

When developing vaccines against viruses, scientists need to understand the chemistry of the virus spike protein. One type of vaccine contains the messenger RNA so that cells can produce the spike proteins themselves and develop immune reactions to them.

One section of mRNA contains the sequence.....GGUGCC.... that codes for glycine and alanine.

Explain how this mRNA sequence enables these two amino acids to form the correct primary structure in a protein.

All amino acids apart from glycine, H₂NCH₂COOH, show optical isomerism.

Describe the feature of the amino acid structure that allows optical isomerism to occur.

Draw two diagrams that show the 3-D relationship between the optical isomers of alanine, H₂NCH(CH₃)COOH.

The primary structure of a protein is the order in which the amino acid residues are bonded together.

Draw a structural formula to show a dipeptide that can be formed when alanine, H₂NCH(CH₃)COOH, and serine, H₂NCH(CH₂OH)COOH, bond together.

Draw a circle around the peptide link.

A student dissolves some solid alanine in distilled water and finds the pH is 6.0.

The student then divides this solution into two separate beakers.

To one beaker the student adds ten drops of dilute hydrochloric acid, and to the other beaker ten drops of dilute sodium hydroxide.

The student finds that the pH of both solutions remains at 6.0.

The formula of the species present in the aqueous solution of alanine is H₃N⁺CH(CH₃)COO^–.

Name this type of species.

Write equations for the reactions that occur in the two beakers.

Equation for reaction with acid (H₃O⁺).

Equation for reaction with alkali (OH –).

The secondary structure of a protein is held together by hydrogen bonds.

Fig. 35.1, shows hydrogen bonding between neighbouring peptide chains in a sheet-type secondary structure.

Fig. 35.1

Describe and explain how a hydrogen bond forms in Fig. 35.1.

* Enzymes are proteins that catalyse certain reactions. They can be used by viruses to infect cells.

The rates of enzyme-catalysed reactions typically vary with substrate concentration as shown in the graph in Fig. 35.2.

Fig. 35.2

The mechanism of an enzyme-catalysed reaction can be written:

State the meaning of the symbols used in the mechanism and explain how this mechanism

accounts for the shape of the curve in Fig. 35.2.