Reactive Chemistry, complete assessment covering reaction evidence, reaction types, metal reactivity, redox, galvanic cells and reaction rates from L01-L12. 15 MC questions (auto-marked) + 5 written questions (self-marked). Complete all questions before submitting.
Which observation is the strongest evidence that a chemical change has occurred rather than only a physical change?
Which equation is the best general pattern for a decomposition reaction?
A precipitation reaction occurs when aqueous ions combine to form:
In complete combustion of a hydrocarbon, the products are:
What gas is produced when an acid reacts with a metal carbonate?
The law of conservation of mass is applied in balancing equations because:
A metal higher in the activity series will generally:
Oxidation is best defined in redox chemistry as:
In a galvanic cell, electrons flow through the external circuit from:
An inert electrode such as graphite is used when:
According to collision theory, increasing temperature increases reaction rate mainly because:
Increasing the surface area of a solid reactant speeds a reaction because it:
A catalyst increases the rate of reaction by:
On a Maxwell-Boltzmann distribution, adding a catalyst is represented by:
What is the purpose of the salt bridge in a galvanic cell?
A student burns propane and also mixes barium chloride solution with sodium sulfate solution. Classify each reaction type, write the expected products for each, and explain the evidence that a chemical reaction has occurred.
Propane combustion is a combustion reaction. Complete combustion forms carbon dioxide and water, for example C3H8 + 5O2 → 3CO2 + 4H2O, with heat and light as evidence. Mixing barium chloride and sodium sulfate is a precipitation reaction because Ba2+ and SO42- form insoluble BaSO4(s). The visible white solid is evidence of a new substance forming.
Marks: 1, combustion classified | 1, correct combustion products/equation | 1, precipitation classified | 1, BaSO4 precipitate identified | 1, evidence linked to new substancesMagnesium is placed in copper(II) sulfate solution. Predict whether a reaction occurs, identify oxidation and reduction, and explain how the same redox pair could be arranged as a galvanic cell.
Magnesium is above copper in the activity series, so it displaces Cu2+ from solution: Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s). Magnesium is oxidised because it loses electrons and its oxidation state rises from 0 to +2. Copper(II) ions are reduced because they gain electrons to form copper metal. In a galvanic cell, Mg would be the anode, Cu2+/Cu the cathode, electrons would flow from Mg to Cu through the wire, and the salt bridge would maintain charge balance.
Marks: 1, prediction from activity series | 1, balanced ionic equation | 1, oxidation identified | 1, reduction identified | 1, galvanic cell electron flow and salt bridge explainedUse collision theory to compare the effect of increasing temperature, increasing concentration and adding a catalyst on reaction rate.
Increasing temperature makes particles move faster, so collisions are more frequent and a larger fraction of collisions have energy at least equal to the activation energy. Increasing concentration places more reactant particles in the same volume, so collision frequency increases. A catalyst provides an alternative reaction pathway with lower activation energy, so a larger fraction of collisions are successful. The catalyst is not consumed and does not change the overall enthalpy change.
Marks: 1, temperature and collision energy | 1, temperature and frequency | 1, concentration and frequency | 1, catalyst lowers Ea | 1, catalyst not consumed/no overall enthalpy changeFor Zn(s) + CuSO4(aq) -> ZnSO4(aq) + Cu(s), assign oxidation states to the reacting metal species, identify the oxidising and reducing agents, and justify your choices.
Zinc begins as Zn(s) with oxidation state 0 and becomes Zn2+ in ZnSO4, so zinc is oxidised. Copper begins as Cu2+ in CuSO4 and becomes Cu(s) with oxidation state 0, so copper(II) ions are reduced. Cu2+ is the oxidising agent because it causes Zn to lose electrons while gaining electrons itself. Zn is the reducing agent because it donates electrons to Cu2+.
Marks: 1, Zn oxidation states | 1, Cu oxidation states | 1, oxidation/reduction identified | 1, oxidising agent justified | 1, reducing agent justifiedExplain how the particle model links visible reaction evidence, balanced equations and reaction rate changes in Reactive Chemistry.
Visible evidence such as gas formation, precipitate formation, colour change or heat release indicates particles have rearranged to form new substances. Balanced equations show this rearrangement while conserving atoms and charge, so coefficients reflect particle ratios. Reaction rate depends on collision frequency and the proportion of collisions with enough energy and correct orientation. Temperature, concentration and surface area change collision frequency or energy distribution, while catalysts lower the activation energy pathway.
Marks: 1, observations linked to new substances | 1, particle rearrangement | 1, conservation in balanced equations | 1, collision frequency/energy | 1, factors and catalyst linked correctly