Chemistry Paper 1 #2 Flashcards
What is the formula for calculating the energy change in a reaction using bond energies?
Energy change = Sum of bond energies of bonds broken - Sum of bond energies of bonds made.
How do you determine if a reaction is exothermic or endothermic from bond energy calculations?
If the energy change is negative, the reaction is exothermic. If positive, the reaction is endothermic.
Write the half-equation for the reaction at the cathode during the electrolysis of aqueous copper(II) sulfate.
Cu²⁺ + 2e⁻ → Cu
Write the half-equation for the reaction at the anode during the electrolysis of aqueous copper(II) sulfate.
4OH⁻ → O₂ + 2H₂O + 4e⁻
Balance the equation for the reaction between sodium and water: Na + H₂O → NaOH + H₂
2Na + 2H₂O → 2NaOH + H₂
Write the ionic equation for the reaction between magnesium and hydrochloric acid.
Mg + 2H⁺ → Mg²⁺ + H₂
Write the balanced equation for the reaction between sulfuric acid and sodium hydroxide.
H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O
What is the result of mixing hydrochloric acid with potassium hydroxide?
They react to form potassium chloride and water (KCl + H₂O).
Why is carbon used in the extraction of metals like iron?
Carbon is used to reduce iron oxide to iron, as it is more reactive than iron but cheaper than electrolysis.
Explain why gold does not corrode or react easily.
Gold is a very unreactive metal, so it does not react with water or oxygen, making it resistant to corrosion.
What is a half-equation for the anode reaction in a hydrogen fuel cell?
2H₂ → 4H⁺ + 4e⁻
What are two environmental advantages of using hydrogen fuel cells?
They produce only water as a by-product and have higher energy efficiency than traditional combustion engines.
Differentiate between a concentrated and a dilute solution.
A concentrated solution has a high amount of solute per volume of solvent, while a dilute solution has a low amount of solute.
What is meant by homolytic fission in bond enthalpy?
Homolytic fission is the process of breaking a bond evenly so that each atom takes one electron, forming radicals.
Explain the purpose of an energy level diagram in reactions.
An energy level diagram shows the energy absorbed or released during a reaction, indicating whether it is exothermic or endothermic.
How does an electrolyte function in an electrochemical cell?
An electrolyte conducts electricity by allowing ions to move, facilitating redox reactions at the electrodes.
What is activation energy, and why is it important?
Activation energy is the minimum energy required to start a reaction by breaking initial bonds; it determines the reaction’s rate.
Define oxidation in terms of electron transfer.
Oxidation is the loss of electrons from a substance during a chemical reaction.
Define reduction in terms of electron transfer.
Reduction is the gain of electrons by a substance during a chemical reaction.
Explain why copper can be found naturally as an uncombined element.
Copper is relatively unreactive and doesn’t readily form compounds, allowing it to be found in its elemental form in nature.
What is meant by ‘standard electrode potential’?
Standard electrode potential is the voltage measured under standard conditions when a half-cell is connected to a standard hydrogen electrode.
