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neurologyYou need to know

• The rate of reaction is the speed at which reactants are changed into products.
• Rate of reaction can be measured by how quickly a product is formed or how quickly a reactant is used up.
• The mean rate of reaction can be calculated using `\text{mean rate}=\frac{\text{quantity of reactant used or product formed}}{\text{time taken}}`.
• When quantity is measured in moles and time is measured in seconds, the unit for rate of reaction is moles per second, written as mol/s.
• On a graph of quantity of product formed against time, a steeper gradient means a faster rate of reaction.
• On a graph of quantity of reactant used up against time, a steeper downward gradient means a faster rate of reaction.
• The gradient of a tangent to a curve gives the rate of reaction at a specific time.
• Rate of reaction usually decreases during a reaction because reactant particles are used up, so there are fewer successful collisions per second.
• The main factors that affect rate of reaction are temperature, concentration, pressure for gases, surface area of solid reactants, and catalysts.
• Collision theory states that reactions happen only when particles collide with enough energy and the correct orientation.
• Increasing temperature increases rate because particles have more kinetic energy, move faster, and a greater proportion of collisions have energy greater than or equal to the activation energy.
• Increasing concentration or pressure increases rate because particles are closer together, so successful collisions happen more often.
• Increasing the surface area of a solid increases rate because more solid particles are exposed for collisions.
• A catalyst increases the rate of reaction without being used up in the reaction.
• A catalyst is not included in the overall chemical equation because it is chemically unchanged at the end of the reaction.
• A catalyst works by providing an alternative reaction pathway with a lower activation energy.
• A reversible reaction is a reaction in which the products can react to form the original reactants.
• A reversible reaction is shown in a chemical equation using the reversible reaction symbol `\rightleftharpoons`.
• If a reversible reaction is exothermic in one direction, it is endothermic by the same amount in the opposite direction.
• Dynamic equilibrium is reached in a closed system when the forward and reverse reactions occur at the same rate and the concentrations of reactants and products remain constant.

• Collect rate of reaction data by measuring a changing quantity, such as gas volume, mass loss, precipitate formation, or concentration, at regular time intervals.
• Calculate the mean rate of reaction from a table or graph by dividing the change in quantity by the time taken, using correct units such as mol/s.
• Plot a rate of reaction graph with time on the x-axis and quantity of product formed or reactant used up on the y-axis, using suitable scales and accurate points.
• Interpret a rate of reaction graph by comparing gradients and identifying when the reaction is fastest, slowing down, or complete.
• Draw a tangent to a curved rate graph at a chosen time, making it touch the curve at that point without cutting across it sharply.
• Calculate the rate at a specific time by finding the gradient of the tangent using `\text{gradient}=\frac{\text{change in }y}{\text{change in }x}`.
• Explain the effect of temperature, concentration, pressure, surface area, or a catalyst on rate using collision frequency and activation energy.
• Identify a catalyst from reaction information by recognising that it increases rate, is regenerated, and does not appear in the overall chemical equation.
• Predict the effect of changing concentration, temperature, or pressure on an equilibrium mixture by applying the idea that the system shifts to oppose the change.
• Interpret given equilibrium data to predict whether the yield of product increases or decreases after a change in temperature, pressure, or concentration.