Which gas is released when many metals react with dilute acids?
Correct answer: A
The metal displaces hydrogen from the acid.
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Which carbon allotrope is used in cutting tools because of its extreme hardness?
Correct answer: D
A strong three-dimensional covalent network gives diamond its hardness.
Which compound is the principal constituent of common salt?
Correct answer: A
Common salt is mainly the ionic compound NaCl.
Which separation method uses differences in boiling points?
Correct answer: D
Vaporisation and condensation separate suitable liquid mixtures.
Which scale expresses acidity or alkalinity of an aqueous solution?
Correct answer: A
Lower pH values indicate greater acidity under comparable conditions.
Which gas is the largest component of dry air by volume?
Correct answer: C
Nitrogen constitutes about 78 percent of dry air.
Which allotrope of carbon conducts electricity through mobile electrons within layers?
Correct answer: D
Its layered bonding leaves electrons able to move.
Which particle in an atom carries a negative charge?
Correct answer: C
Electrons occupy regions outside the nucleus.
What is a substance that changes reaction rate without being consumed overall called?
Correct answer: A
A catalyst provides an alternative reaction pathway.
Which separation method separates an insoluble solid from a liquid using a porous barrier?
Correct answer: C
The filter retains solid particles while fluid passes through.
Which gas turns limewater milky?
Correct answer: B
It forms a calcium carbonate precipitate in limewater.
What is the slow oxidation of iron in the presence of air and moisture called?
Correct answer: D
Rust consists mainly of hydrated iron oxides.
Which particle carries a positive charge in the nucleus?
Correct answer: C
The proton count determines the atomic number.
Which gas supports ordinary combustion but is not itself a fuel?
Correct answer: C
Combustion commonly involves reaction with oxygen.
Which nuclear particle has no net electric charge?
Correct answer: D
Neutrons contribute to nuclear mass without net charge.
Evaluate the two proposed answers. Which are supported? I. Pouring clear liquid off a settled solid — the appropriate term: Ion exchange. II. Particles settling from a suspension under gravity — the appropriate term: Chromatography.
Correct answer: B
I is incorrect: Pouring clear liquid off a settled solid → Decantation. It separates liquid from sediment without filtration. II is incorrect: Particles settling from a suspension under gravity → Sedimentation. Heavier suspended particles accumulate at the bottom.
Evaluate the two proposed answers. Which are supported? I. Mixture of two or more metals, or a metal and another element — the appropriate term: Deposition. II. Splitting a compound using electric current — the appropriate term: Electrolysis.
Correct answer: C
I is incorrect: Mixture of two or more metals, or a metal and another element → Alloy. Alloying can alter strength, hardness or corrosion resistance. II is correct: Splitting a compound using electric current → Electrolysis. Electrical energy drives a chemical transformation.
For Separating coloured components by different movement on a medium, identify the appropriate term.
Correct answer: B
Components differ in their interaction with mobile and stationary phases.
Evaluate the two proposed answers. Which are supported? I. Loss of electrons by a species — the appropriate term: Neutralisation. II. Reaction of an acid with a base to produce salt and water — the appropriate term: Electrolysis.
Correct answer: D
I is incorrect: Loss of electrons by a species → Oxidation. Electron loss increases oxidation state. II is incorrect: Reaction of an acid with a base to produce salt and water → Neutralisation. Hydrogen and hydroxide ions can combine to form water.
Evaluate the two proposed answers. Which are supported? I. Solid changing directly into gas — the appropriate term: Sublimation. II. Removal of hardness using exchange of dissolved ions — the appropriate term: Isobars.
Correct answer: C
I is correct: Solid changing directly into gas → Sublimation. The liquid phase is bypassed under the given conditions. II is incorrect: Removal of hardness using exchange of dissolved ions → Ion exchange. Suitable resins replace hardness-causing ions.
For Particles settling from a suspension under gravity, identify the appropriate term.
Correct answer: A
Heavier suspended particles accumulate at the bottom.
Evaluate the two proposed answers. Which are supported? I. Atoms with equal proton number but different mass number — the appropriate term: Isotopes. II. Pouring clear liquid off a settled solid — the appropriate term: Ion exchange.
Correct answer: B
I is correct: Atoms with equal proton number but different mass number → Isotopes. Different neutron counts change mass without changing element identity. II is incorrect: Pouring clear liquid off a settled solid → Decantation. It separates liquid from sediment without filtration.
Evaluate the two proposed answers. Which are supported? I. Mixture of two or more metals, or a metal and another element — the appropriate term: Sedimentation. II. Gain of electrons by a species — the appropriate term: Reduction.
Correct answer: D
I is incorrect: Mixture of two or more metals, or a metal and another element → Alloy. Alloying can alter strength, hardness or corrosion resistance. II is correct: Gain of electrons by a species → Reduction. Electron gain lowers oxidation state.
For Reaction of an acid with a base to produce salt and water, identify the appropriate term.
Correct answer: C
Hydrogen and hydroxide ions can combine to form water.
Evaluate the two proposed answers. Which are supported? I. Coating an object with metal using electric current — the appropriate term: Electroplating. II. Gas changing directly into solid — the appropriate term: Decantation.
Correct answer: D
I is correct: Coating an object with metal using electric current → Electroplating. Metal ions are reduced onto an electrode surface. II is incorrect: Gas changing directly into solid → Deposition. This is the reverse phase change of sublimation.