Rates Of Reaction Flashcards
How can you find the rate of reaction?
The rate of reaction can be found by measuring the amount of product formed, or the amount of product lost, over a certain period of time.
Rate is most often calculated using the equation: rate = 1/time where the time is the time for the reaction to reach a certain point or the time for the reaction to be completed. The units of rate calculated in this way are s-1.
How can you analyse the rate of reaction using a graph?
The rate of reaction can be analysed by plotting a graph of amount of product against time.
Compared to the slow reaction, the graph line for the faster reaction:
has a steeper gradient at the start
becomes horizontal sooner (gas stops being produced sooner so the reaction finishes sooner) meaning that the rate of reaction is greater.
What is the minimum amount of energy for a successful collision called?
The minimum amount of energy for a collision to be successful is called the
activation energy.
How can altering the temperature change the rate of a reaction?
If the temperature is increased:
the reactant particles move more quickly
they have more energy
there are more successful collisions per unit time
the rate of reaction increases
How can altering the concentration change the rate of a reaction?
If the concentration is increased:
there are more reactant particles
there are more successful collision per unit time
the rate of reaction increases
How can altering the particle size (surface area) change the rate of a reaction?
The rate of a chemical reaction can be increased by using smaller solid particles which increases the surface area of a solid reactant. This is done by cutting the substance into small pieces, or by grinding it into a powder. If the surface area of a reactant is increased:
more particles are exposed to the other reactant
there are more successful collisions per unit time
the rate of reaction increases
What will catalysts do to the rate of a reaction?
The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which increases the rate of a chemical reaction but it is not used up (remains chemically unchanged at the end).
What does the amount of catalyst not used up do in a reaction?
The amount of catalyst not used up provides an alternative reaction pathway of lower activation energy.
How do you react a metal with a dilute acid? (Practical)
(See diagram)
We can use a gas syringe to measure the reaction of metals with dilute acid. When zinc reacts with hydrochloric acid it produces zinc chloride and hydrogen gas.
We can measure the rate of the reaction by measuring how fast the reaction produces hydrogen. This requires a conical flask and gas syringe.
Zn + HCl → ZnCl2 + H2
How do you react calcium carbonate with dilute acid? (Practical)
Similarly, when calcium carbonate reacts with dilute hydrochloric acid, it produces carbon dioxide gas. We can measure the rate of the reaction by measuring how fast the reaction produces carbon dioxide. This requires a conical flask and gas syringe.
CaCO3+ HCl → CaCl2 + CO2 + H2O
What Is Catalytic decomposition of hydrogen peroxide? (Practical)
Hydrogen peroxide decomposes in the presence of a catalyst like manganese dioxide, iron, or copper(II)oxide to produce oxygen and water. We can measure how each catalyst affects the rate of the reaction by measuring how fast it produces oxygen. The same apparatus is used – alternatively you can replace the gas syringe with a measuring cylinder filled with water and inverted in a trough of water.
2H2O2 → O2 + 2H2O
What is Sodium thiosulfate reaction with acid? (Practical)
Sodium thiosulfate reacts with dilute hydrochloric acid to produce sodium chloride, water, sulfur dioxide and sulfur. The sulfur makes the solution change to opaque and if the conical flask is placed over an X drawn on a piece of paper we can measure the time taken for the X not to be visible when viewed from above.
1/time gives a measure of the rate of the reaction.
