Chemistry Paper 1 #3 Flashcards
(23 cards)
What is the purpose of electrolysis?
Electrolysis is used to decompose ionic compounds into their constituent elements by passing an electric current.
What are the products at the anode and cathode in the electrolysis of aqueous sodium chloride?
At the anode, chlorine gas is produced, and at the cathode, hydrogen gas is produced as sodium remains in solution.
What factors determine the discharge of ions in the electrolysis of an aqueous solution?
The discharge depends on the reactivity of ions: less reactive cations and specific anions (like halides) are discharged preferentially.
What is the significance of the reactivity series in metal extraction?
The reactivity series predicts the method of extraction: metals above carbon require electrolysis, while those below can be reduced by carbon.
Name two metals that do not react with dilute acids.
Copper and silver do not react with dilute acids because they are less reactive than hydrogen.
What is a redox reaction?
A redox reaction is one where oxidation and reduction occur simultaneously; one substance gains electrons while another loses electrons.
Identify the oxidizing and reducing agents in the reaction: Zn + CuSO₄ → ZnSO₄ + Cu
Zn is the reducing agent (it loses electrons), and Cu²⁺ is the oxidizing agent (it gains electrons).
What is a neutralisation reaction and give an example.
A neutralisation reaction is when an acid reacts with a base to form water and a salt. Example: HCl + NaOH -> NaCl + H₂O.
Define pH and explain what a pH of 7 represents.
pH is a measure of hydrogen ion concentration. A pH of 7 represents a neutral solution where [H⁺] equals [OH⁻].
What distinguishes a strong acid from a weak acid?
A strong acid fully dissociates in water, while a weak acid only partially dissociates, producing fewer hydrogen ions in solution.
What is the difference between exothermic and endothermic reactions?
Exothermic reactions release energy to the surroundings (temperature rises), while endothermic reactions absorb energy (temperature falls).
Give an example of an exothermic reaction and an endothermic reaction.
Exothermic: Combustion of methane. Endothermic: Dissolving ammonium nitrate in water.
How do you calculate the energy change of a reaction using bond energies?
Energy change = Sum of bond energies of bonds broken - Sum of bond energies of bonds made.
What does a negative energy change in bond energy calculations indicate?
A negative energy change indicates an exothermic reaction, where more energy is released in bond-making than consumed in bond-breaking.
How does an electrochemical cell produce electricity?
It produces electricity by a redox reaction between two metals with different reactivities in an electrolyte, generating electron flow.
Describe the function of the anode and cathode in a Daniell cell.
In a Daniell cell, the anode is where oxidation occurs (zinc loses electrons), and the cathode is where reduction occurs (copper gains electrons).
What is a hydrogen fuel cell, and what are its products?
A hydrogen fuel cell converts hydrogen and oxygen into electricity, producing water and releasing heat as by-products.
List two advantages and two disadvantages of hydrogen fuel cells.
Advantages: No harmful emissions, high efficiency. Disadvantages: Difficult storage of hydrogen, high production costs.
What is activation energy?
Activation energy is the minimum energy required to initiate a chemical reaction by breaking bonds in the reactants.
How does the reactivity of metals relate to their position in the reactivity series?
Metals higher in the reactivity series are more reactive and readily lose electrons to form positive ions.
What is a displacement reaction?
A displacement reaction is when a more reactive metal displaces a less reactive metal from its compound.
Define spectator ion and give an example in a reaction.
A spectator ion is an ion that does not participate in the reaction. Example: SO₄²⁻ in the reaction between Zn and CuSO₄.
What is bond enthalpy?
Bond enthalpy is the energy needed to break one mole of a bond in a gaseous molecule, measured in kJ/mol.
