OCR A LEVEL CHEMISTRY B
(SALTERS) PAPER 1 PRACTICE
EXAM – 200 Q&A WITH
RATIONALES (2025/2026)
OCR A-Level Chemistry B (Salters) Practice Exam
Question 1
A student synthesizes a sample of aspirin (\(M_r =
180.2\,\text{g}\,\text{mol}^{-1}\)) from salicylic acid (\(M_r =
138.1\,\text{g}\,\text{mol}^{-1}\)) and ethanoic anhydride (\(M_r =
102.1\,\text{g}\,\text{mol}^{-1}\)). The equation for the reaction is:
\(\text{C}_7\text{H}_6\text{O}_3 + \text{C}_4\text{H}_6\text{O}_3
\rightarrow \text{C}_9\text{H}_8\text{O}_4 +
\text{CH}_3\text{COOH}\). What is the percentage atom economy for
the production of aspirin?
A. 55.4%
B. 60.0%
C. 75.0%
D. 100%
Rationale: Atom economy is calculated by dividing the molar mass of
the desired product by the total molar mass of all reactants, multiplied
by 100. \(\text{Atom Economy} = [180.2 / (138.1 + 102.1)] \times 100 =
[180..2] \times 100 = 75.02\%\).
Question 2
Infrared spectroscopy is widely used to monitor the progress of organic
reactions by observing functional group transformations. Which of the
following infrared absorptions would disappear when a sample of
propan-2-ol is completely oxidized to propanone?
A. A strong, sharp absorption at \(1700\text{–}1750\,\text{cm}^{-1}\)
B. A strong, broad absorption at \(3200\text{–
}3600\,\text{cm}^{-1}\)
C. A weak, narrow absorption at \(2200\text{–}2250\,\text{cm}^{-1}\)
D. A strong, sharp absorption at \(1000\text{–}1300\,\text{cm}^{-1}\)
Rationale: Propan-2-ol is a secondary alcohol containing an O–H
bond, which produces a characteristic broad absorption peak between
,\(3200\text{–}3600\,\text{cm}^{-1}\). Upon oxidation to propanone
(a ketone), the alcohol O–H bond is lost and a carbonyl group (C=O)
peak appears instead.
Question 3
The atmospheric greenhouse effect depends significantly on the specific
interaction of trace gases with escaping planetary thermal radiation.
Which atmospheric gas does not contribute to the greenhouse effect
because it cannot undergo a change in dipole moment during vibration?
A. \(\text{H}_2\text{O}\)
B. \(\text{CO}_{2}\)
C. \(\text{CH}_{4}\)
D. \(\text{N}_{2}\)
Rationale: For a gas to absorb infrared radiation and act as a
greenhouse gas, its molecular vibrations must cause a temporary
change in its dipole moment. Homonuclear diatomic molecules like
\(\text{N}_{2}\) possess zero dipole moment both at rest and during
vibration, making them IR-inactive.
Question 4
A sample of an unknown organic liquid is analyzed using a time-of-flight
mass spectrometer. The spectrum reveals a molecular ion peak
(\(M^{+}\)) at an \(m/z\) ratio of 72, alongside a significantly smaller
peak (\(M+1\)) at \(m/z = 73\). What is the primary cause of the
\(M+1\) peak?
A. Contamination of the sample with an impurity of higher molecular
mass
B. Fragment ions that have captured an extra lone pair of electrons
C. The natural abundance of the carbon-13 isotope in the
organic molecules
D. Incomplete ionization resulting in stable dicationic species
Rationale: The \(M+1\) peak in organic mass spectra arises due to the
presence of the stable, naturally occurring \(^{13}\text{C}\) isotope,
which has an approximate relative cosmic abundance of 1.11%
compared to \(^{12}\text{C}\).
Question 5
Transition elements are known for forming a wide variety of colored
coordination complexes due to electronic transitions within their
partially filled d-orbitals. What is the correct oxidation state of the iron
,central metal ion in the complex ion \([\text{Fe}(\text{CN})_6]^{3-}\)?
A. +2
B. +3
C. +4
D. +6
Rationale: Cyanide ions (\(\text{CN}^{-}\)) carry a formal charge of –
1. Let \(x\) be the oxidation state of iron: \(x + 6(–1) = –3\), which
simplifies to \(x – 6 = –3\), giving \(x = +3\).
Question 6
Halogen reactivity shows clear vertical periodic trends determined by
atomic size and shielding effects. Which statement correctly describes
the trend in oxidizing ability of the halogens down Group 17?
A. It increases because the outer electrons are closer to the atomic
nucleus
B. It increases because the nuclear charge increases down the group
C. It decreases because the atomic radius and electron
shielding increase
D. It decreases because the electronegativity increases down the group
Rationale: Down Group 17, atomic radius and inner-shell electron
shielding increase. This makes it more difficult for the larger atoms to
attract and gain an extra electron into their outer shell, decreasing
their power as oxidizing agents.
Question 7
A buffer solution must resist changes in pH when small quantities of acid
or alkali are added to it. Which of the following mixtures will generate an
effective acidic buffer system when mixed in equal volumes?
A. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{HCl}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{NaCl}\)
B. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{CH}_3\text{COOH}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{HCl}\)
C. \(0.2\,\text{mol}\,\text{dm}^{-
3}\,\text{CH}_3\text{COOH}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{NaOH}\)
D. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{CH}_3\text{COOH}\) and
\(0.2\,\text{mol}\,\text{dm}^{-3}\,\text{NaOH}\)
Rationale: Mixing \(0.2\,\text{mol}\,\text{dm}^{-3}\) of weak acid
(\(\text{CH}_3\text{COOH}\)) with \(0.1\,\text{mol}\,\text{dm}^{-
3}\) of strong base (\(\text{NaOH}\)) results in partial neutralization.
, This leaves a solution containing an excess of weak acid alongside its
conjugate base (\(\text{CH}_3\text{COO}^-\)), creating an acidic
buffer.
Question 8
What is the IUPAC systematic name for the branched organic compound
shown below?
\(\text{CH}_{3}\text{CH}(\text{CH}_{3})\text{CH}_{2}\text{CH}=\te
xt{CH}_{2}\)
A. 2-methylpent-4-ene
B. 4-methylpent-1-ene
C. 2-methylpent-1-ene
D. 4-methylpent-2-ene
Rationale: The carbon chain must be numbered starting from the end
closest to the principal functional group, which is the alkene double
bond. This gives the alkene a position of carbon-1, placing the methyl
branch at carbon-4.
Question 9
Amines react via distinct mechanisms depending on their chemical
environment. What type of reaction mechanism takes place when
ammonia reacts with a bromoalkane to form a primary amine?
A. Electrophilic addition
B. Electrophilic substitution
C. Nucleophilic substitution
D. Nucleophilic addition
Rationale: Ammonia acts as a nucleophile because it possesses a lone
pair of electrons on its nitrogen atom. It attacks the electron-deficient
carbon atom bonded to the halogen, displacing the bromide ion in a
nucleophilic substitution reaction.
Question 10
The subshell electronic configuration of transition metal atoms and ions
often features unique stability variations. What is the correct ground-
state electronic configuration of a copper(II) ion, \(\text{Cu}^{2+}\)?
A. \([\text{Ar}] 3\text{d}^8 4\text{s}^1\)
B. \([\text{Ar}] 3\text{d}^{10}\)
C. \([\text{Ar}] 3\text{d}^9\)
D. \([\text{Ar}] 3\text{d}^7 4\text{s}^2\)
Rationale: A neutral copper atom has an exceptional electronic
(SALTERS) PAPER 1 PRACTICE
EXAM – 200 Q&A WITH
RATIONALES (2025/2026)
OCR A-Level Chemistry B (Salters) Practice Exam
Question 1
A student synthesizes a sample of aspirin (\(M_r =
180.2\,\text{g}\,\text{mol}^{-1}\)) from salicylic acid (\(M_r =
138.1\,\text{g}\,\text{mol}^{-1}\)) and ethanoic anhydride (\(M_r =
102.1\,\text{g}\,\text{mol}^{-1}\)). The equation for the reaction is:
\(\text{C}_7\text{H}_6\text{O}_3 + \text{C}_4\text{H}_6\text{O}_3
\rightarrow \text{C}_9\text{H}_8\text{O}_4 +
\text{CH}_3\text{COOH}\). What is the percentage atom economy for
the production of aspirin?
A. 55.4%
B. 60.0%
C. 75.0%
D. 100%
Rationale: Atom economy is calculated by dividing the molar mass of
the desired product by the total molar mass of all reactants, multiplied
by 100. \(\text{Atom Economy} = [180.2 / (138.1 + 102.1)] \times 100 =
[180..2] \times 100 = 75.02\%\).
Question 2
Infrared spectroscopy is widely used to monitor the progress of organic
reactions by observing functional group transformations. Which of the
following infrared absorptions would disappear when a sample of
propan-2-ol is completely oxidized to propanone?
A. A strong, sharp absorption at \(1700\text{–}1750\,\text{cm}^{-1}\)
B. A strong, broad absorption at \(3200\text{–
}3600\,\text{cm}^{-1}\)
C. A weak, narrow absorption at \(2200\text{–}2250\,\text{cm}^{-1}\)
D. A strong, sharp absorption at \(1000\text{–}1300\,\text{cm}^{-1}\)
Rationale: Propan-2-ol is a secondary alcohol containing an O–H
bond, which produces a characteristic broad absorption peak between
,\(3200\text{–}3600\,\text{cm}^{-1}\). Upon oxidation to propanone
(a ketone), the alcohol O–H bond is lost and a carbonyl group (C=O)
peak appears instead.
Question 3
The atmospheric greenhouse effect depends significantly on the specific
interaction of trace gases with escaping planetary thermal radiation.
Which atmospheric gas does not contribute to the greenhouse effect
because it cannot undergo a change in dipole moment during vibration?
A. \(\text{H}_2\text{O}\)
B. \(\text{CO}_{2}\)
C. \(\text{CH}_{4}\)
D. \(\text{N}_{2}\)
Rationale: For a gas to absorb infrared radiation and act as a
greenhouse gas, its molecular vibrations must cause a temporary
change in its dipole moment. Homonuclear diatomic molecules like
\(\text{N}_{2}\) possess zero dipole moment both at rest and during
vibration, making them IR-inactive.
Question 4
A sample of an unknown organic liquid is analyzed using a time-of-flight
mass spectrometer. The spectrum reveals a molecular ion peak
(\(M^{+}\)) at an \(m/z\) ratio of 72, alongside a significantly smaller
peak (\(M+1\)) at \(m/z = 73\). What is the primary cause of the
\(M+1\) peak?
A. Contamination of the sample with an impurity of higher molecular
mass
B. Fragment ions that have captured an extra lone pair of electrons
C. The natural abundance of the carbon-13 isotope in the
organic molecules
D. Incomplete ionization resulting in stable dicationic species
Rationale: The \(M+1\) peak in organic mass spectra arises due to the
presence of the stable, naturally occurring \(^{13}\text{C}\) isotope,
which has an approximate relative cosmic abundance of 1.11%
compared to \(^{12}\text{C}\).
Question 5
Transition elements are known for forming a wide variety of colored
coordination complexes due to electronic transitions within their
partially filled d-orbitals. What is the correct oxidation state of the iron
,central metal ion in the complex ion \([\text{Fe}(\text{CN})_6]^{3-}\)?
A. +2
B. +3
C. +4
D. +6
Rationale: Cyanide ions (\(\text{CN}^{-}\)) carry a formal charge of –
1. Let \(x\) be the oxidation state of iron: \(x + 6(–1) = –3\), which
simplifies to \(x – 6 = –3\), giving \(x = +3\).
Question 6
Halogen reactivity shows clear vertical periodic trends determined by
atomic size and shielding effects. Which statement correctly describes
the trend in oxidizing ability of the halogens down Group 17?
A. It increases because the outer electrons are closer to the atomic
nucleus
B. It increases because the nuclear charge increases down the group
C. It decreases because the atomic radius and electron
shielding increase
D. It decreases because the electronegativity increases down the group
Rationale: Down Group 17, atomic radius and inner-shell electron
shielding increase. This makes it more difficult for the larger atoms to
attract and gain an extra electron into their outer shell, decreasing
their power as oxidizing agents.
Question 7
A buffer solution must resist changes in pH when small quantities of acid
or alkali are added to it. Which of the following mixtures will generate an
effective acidic buffer system when mixed in equal volumes?
A. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{HCl}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{NaCl}\)
B. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{CH}_3\text{COOH}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{HCl}\)
C. \(0.2\,\text{mol}\,\text{dm}^{-
3}\,\text{CH}_3\text{COOH}\) and
\(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{NaOH}\)
D. \(0.1\,\text{mol}\,\text{dm}^{-3}\,\text{CH}_3\text{COOH}\) and
\(0.2\,\text{mol}\,\text{dm}^{-3}\,\text{NaOH}\)
Rationale: Mixing \(0.2\,\text{mol}\,\text{dm}^{-3}\) of weak acid
(\(\text{CH}_3\text{COOH}\)) with \(0.1\,\text{mol}\,\text{dm}^{-
3}\) of strong base (\(\text{NaOH}\)) results in partial neutralization.
, This leaves a solution containing an excess of weak acid alongside its
conjugate base (\(\text{CH}_3\text{COO}^-\)), creating an acidic
buffer.
Question 8
What is the IUPAC systematic name for the branched organic compound
shown below?
\(\text{CH}_{3}\text{CH}(\text{CH}_{3})\text{CH}_{2}\text{CH}=\te
xt{CH}_{2}\)
A. 2-methylpent-4-ene
B. 4-methylpent-1-ene
C. 2-methylpent-1-ene
D. 4-methylpent-2-ene
Rationale: The carbon chain must be numbered starting from the end
closest to the principal functional group, which is the alkene double
bond. This gives the alkene a position of carbon-1, placing the methyl
branch at carbon-4.
Question 9
Amines react via distinct mechanisms depending on their chemical
environment. What type of reaction mechanism takes place when
ammonia reacts with a bromoalkane to form a primary amine?
A. Electrophilic addition
B. Electrophilic substitution
C. Nucleophilic substitution
D. Nucleophilic addition
Rationale: Ammonia acts as a nucleophile because it possesses a lone
pair of electrons on its nitrogen atom. It attacks the electron-deficient
carbon atom bonded to the halogen, displacing the bromide ion in a
nucleophilic substitution reaction.
Question 10
The subshell electronic configuration of transition metal atoms and ions
often features unique stability variations. What is the correct ground-
state electronic configuration of a copper(II) ion, \(\text{Cu}^{2+}\)?
A. \([\text{Ar}] 3\text{d}^8 4\text{s}^1\)
B. \([\text{Ar}] 3\text{d}^{10}\)
C. \([\text{Ar}] 3\text{d}^9\)
D. \([\text{Ar}] 3\text{d}^7 4\text{s}^2\)
Rationale: A neutral copper atom has an exceptional electronic
