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How can the rate of a chemical reaction be determined?
The rate of a chemical reaction can be found by measuring the quantity of a reactant used or the quantity of a product formed over time.
What is the formula for calculating the mean rate of reaction based on the quantity of reactant used?
The formula is: mean rate of reaction = quantity of reactant used / time taken.
What is the formula for calculating the mean rate of reaction based on the quantity of product formed?
The formula is: mean rate of reaction = quantity of product formed / time taken.
What units are used to measure the rate of reaction?
The units for rate of reaction may be given as g/s (grams per second) or cm³/s (cubic centimeters per second).
What additional units are used for rate of reaction in the Higher Tier?
In the Higher Tier, the rate of reaction can be expressed in mol/s (moles per second).
What is a tangent in the context of reaction rate graphs?
A tangent is a straight line that touches a curve at a single point and can be used to measure the rate of reaction by calculating its slope.
How is the gradient of a tangent used in Higher Tier calculations?
In Higher Tier, students calculate the gradient of a tangent to the curve as a measure of the rate of reaction at a specific time.
What factors can affect the rate of a chemical reaction?
The concentration of reactants in solution.
The pressure of reacting gases.
Surface area of solid reactants.
Temperature.
Presence of catalysts.
How does increasing the concentration of reactants affect the rate of reaction?
Increasing the concentration of reactants typically increases the rate of reaction by increasing the frequency of collisions between particles.
How does increasing the pressure of reacting gases affect the rate of reaction?
Increasing the pressure of reacting gases usually increases the rate of reaction by forcing more collisions between particles.
How does increasing the surface area of solid reactants affect the rate of reaction?
Increasing the surface area of solid reactants speeds up the reaction by allowing more particles to collide with the reactants' surface.
How does increasing the temperature affect the rate of reaction?
Increasing the temperature increases the rate of reaction because particles move faster and collide more frequently with greater energy.
What role do catalysts play in chemical reactions?
Catalysts increase the rate of a reaction by providing an alternative pathway with a lower activation energy, without being consumed in the process.
What does collision theory explain?
Collision theory explains how various factors affect the rates of reactions.
What is required for a chemical reaction to occur according to collision theory?
According to collision theory, chemical reactions occur when reacting particles collide with sufficient energy.
What is the minimum amount of energy required for particles to react called?
The minimum amount of energy that particles must have to react is called the activation energy.
How does the size of reacting solids affect the rate of reaction?
Decreasing the size of reacting solid pieces increases the surface area to volume ratio, which increases the rate of reaction.
What is unique about catalysts in terms of the reaction equation?
Catalysts are not included in the chemical equation because they are not used up in the reaction.
What is the role of enzymes in biological systems?
Enzymes act as biological catalysts, speeding up reactions in living organisms without being consumed.
What are reversible reactions?
Reversible reactions are chemical reactions where the products can react to form the original reactants. They are represented as A + B ⇌ C + D.
How can the direction of a reversible reaction be changed?
The direction of a reversible reaction can be changed by altering the conditions, such as temperature or pressure.
If a reversible reaction is exothermic in one direction, what is true about the reverse direction?
If a reversible reaction is exothermic in one direction, it is endothermic in the reverse direction. The same amount of energy is transferred in each case.
What is equilibrium in the context of reversible reactions?
Equilibrium is reached in a reversible reaction when the forward and reverse reactions occur at exactly the same rate in a closed system, preventing the escape of reactants and products.
How does increasing the temperature affect equilibrium in an endothermic reaction?
Increasing the temperature in an endothermic reaction increases the relative amount of products at equilibrium.
How does increasing the temperature affect equilibrium in an exothermic reaction?
Increasing the temperature in an exothermic reaction decreases the relative amount of products at equilibrium.
How does decreasing the temperature affect equilibrium in an endothermic reaction?
Decreasing the temperature in an endothermic reaction decreases the relative amount of products at equilibrium.
How does decreasing the temperature affect equilibrium in an exothermic reaction?
Decreasing the temperature in an exothermic reaction increases the relative amount of products at equilibrium.
For gaseous reactions at equilibrium, how does increasing the pressure affect the equilibrium position?
Increasing the pressure causes the equilibrium position to shift towards the side with the smaller number of molecules.
For gaseous reactions at equilibrium, how does decreasing the pressure affect the equilibrium position?
Decreasing the pressure causes the equilibrium position to shift towards the side with the larger number of molecules.
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