⚗️ • Lesson 2.4 : Chemical Energetics, Acids, Bases and Salts (Chem) Flashcards
In this long deck, we will go through exothermic and endothermic reactions, physical and chemical changes, the rate of reaction, redox, as well as the characteristics and properties of acids and bases, oxides, and the preparation of salts.
What is an exothermic reaction?
A reaction that transfers thermal energy to the surroundings, increasing the temperature of the surroundings.
What is an endothermic reaction?
A reaction that takes in thermal energy from the surroundings, decreasing the temperature of the surroundings.
What do reaction pathway diagrams show?
They show whether a reaction is exothermic or endothermic by comparing the energy of reactants and products.
What is the enthalpy change (∆H) of a reaction?
It is the transfer of thermal energy during a reaction.
∆H is negative for exothermic reactions and positive for endothermic reactions.
What is activation energy (Ea)?
The minimum energy that colliding particles must have to react.
What labels must be included in a reaction pathway diagram?
Reactants, products, overall energy change (∆H), and activation energy (Ea).
Is bond breaking endothermic or exothermic?
Endothermic — it requires energy.
Is bond making endothermic or exothermic?
Exothermic — It releases energy.
What is the difference between a physical change and a chemical change?
A physical change doesn’t alter the chemical composition of a substance,
while a chemical change results in the formation of a new substance.
How does changing the concentration of solutions affect the rate of reaction?
Increasing concentration increases the rate of reaction because there are more reactant particles to collide.
How does changing the pressure of gases affect the rate of reaction?
Increasing pressure increases the rate of reaction because the gas particles are closer together, leading to more frequent collisions.
How does changing the surface area of solids affect the rate of reaction?
Increasing the surface area increases the rate of reaction by providing more area for collisions to occur.
How does changing the temperature affect the rate of reaction?
Increasing temperature increases the rate of reaction by giving particles more energy, causing them to collide more often and with more force.
How does adding or removing a catalyst affect the rate of reaction?
A catalyst increases the rate of reaction by lowering the activation energy, without being consumed in the reaction.
How does collision theory explain the rate of reaction in terms of the number of particles per unit volume?
A higher number of particles per unit volume increases the rate of reaction by increasing the frequency of collisions between reactant particles.
What does a catalyst do to the activation energy of a reaction?
A catalyst decreases the activation energy, making it easier for reactions to occur.
How can the rate of reaction be practically investigated?
By measuring changes in mass, volume of gas produced, or time taken for the reaction to complete.
How does collision theory explain the rate of reaction in terms of the frequency of collisions between particles?
The more frequent the collisions between particles, the higher the rate of reaction, as there are more opportunities for particles to react.
How does collision theory explain the rate of reaction in terms of the kinetic energy of particles?
Higher kinetic energy of particles results in more energetic collisions, increasing the likelihood of a successful reaction.
How does collision theory explain the rate of reaction in terms of activation energy (Ea)?
A reaction occurs when particles collide with sufficient energy to overcome the activation energy barrier, which is the minimum energy required for the reaction.
What are redox reactions?
Redox reactions involve both oxidation (loss of electrons) and reduction (gain of electrons) occurring simultaneously.
What is oxidation in terms of the gain of oxygen and loss of electrons?
Oxidation is the process of a substance gaining oxygen during a chemical reaction, and it involves the loss of electrons by a substance.
What is oxidation in terms of an increase in oxidation number?
Oxidation occurs when the oxidation number of an element increases during a reaction.
What is reduction in terms of gain of electrons?
Reduction is the process where a substance gains electrons during a chemical reaction.
What is reduction in terms of a decrease in oxidation number?
Reduction occurs when the oxidation number of an element decreases during a chemical reaction.
What are redox reactions in terms of oxygen gain and loss?
Redox reactions involve the gain of oxygen by one substance (oxidation) and the loss of oxygen by another substance (reduction).
What are the characteristic properties of acids when reacting with metals?
Acids react with metals to produce hydrogen gas and a salt.
What are the characteristic properties of acids when reacting with bases?
Acids react with bases to form a salt and water in a neutralisation reaction.
What are the characteristic properties of acids when reacting with carbonates?
Acids react with carbonates to produce carbon dioxide gas, water, and a salt.
How do acids affect the indicators litmus and methyl orange?
Acids turn litmus paper red and methyl orange red.
What are bases, and what are alkalis?
Bases are oxides or hydroxides of metals, and alkalis are soluble bases that dissolve in water.
How do bases react with acids?
Bases react with acids to form a salt and water in a neutralisation reaction.
How do alkalis affect the indicators litmus and methyl orange?
Alkalis turn litmus paper blue and methyl orange yellow.
How can you compare neutrality, relative acidity, and relative alkalinity using universal indicator?
Universal indicator shows different colors depending on the pH,
Red = acidic (pH 0-6)
Green = neutral, (pH 7)
Blue/purple = alkaline (pH 8-14)
What is the neutralisation reaction between an acid and an alkali?
The neutralisation reaction between an acid and an alkali produces a salt and water. The ionic equation is not required for this reaction.
How can oxides be classified based on their character?
Oxides can be classified as acidic (ex. SO₂ and CO₂) or basic (ex. CuO and CaO) based on whether the oxide is metallic or non-metallic.
What are amphoteric oxides?
Amphoteric oxides are oxides that can react with both acids and bases to produce a salt and water.
Which oxides are amphoteric?
Al₂O₃ and ZnO are examples of amphoteric oxides.
(Aluminium Oxide and Zinc Oxide)
How is a soluble salt prepared by titration?
Mix an acid with an alkali in exact proportions using a burette and a pH indicator. Evaporate the water to crystallize the salt.
How is a soluble salt prepared when reacting an acid with excess metal?
Add excess metal to an acid; the metal reacts to form a salt and hydrogen. Filter out the metal and purify the salt.
How is a soluble salt prepared when reacting an acid with excess insoluble base?
Add excess base to an acid; filter out the excess base, then crystallize the salt.
How is a soluble salt prepared when reacting an acid with excess insoluble carbonate?
Add excess carbonate to an acid; filter out the excess, then crystallize the salt.
What is a hydrated substance?
A hydrated substance is a substance that is chemically combined with water.
What is an anhydrous substance?
An anhydrous substance is a substance that contains no water.
How are insoluble salts prepared by precipitation?
Mix two solutions containing soluble salts. The insoluble salt forms as a precipitate, which is then filtered, washed, and dried.
