Chapter 10 Flashcards
Definition of rate of reaction.
How fast a reactant is used up/how fast a product is formed.
Name four factors which affect the rate of reaction.
Temperature, Concentration/pressure (g). catalyst, surface area (s only)
Explain how a higher concentration/pressure results in an increased rate.
Conc= more particles per unit of volume so more frequent collisions. Pressure= smaller volume increases gas pressure as molecules collide more frequently.
What does collision theory state?
The particles must collide to react, but at the right angle and with more energy than the Activation Energy.
What is the definition of a catalyst and its function?
A substance that increases the rate of a chemical reaction without undergoing any permanent change. It provides an alternate pathway with a lower activation energy. (may form an intermediate or provide a surface on which the reaction takes place).
What is a homogenous catalyst?
Has the same physical state as the reactants. e.g an enzyme
What is a heterogenous catalyst and how does it work?
Has a different physical state as the reactants. 1. Reactant molecules form weak bonds to catalyst’s surface (adsorption). 2. Bonds within the reactant molecules break. 3. New bonds form within the reactants. 4. Product molecules leave the catalyst’s surface (desorption).
How does a catalyst being used in an industrial reaction result in less CO2 emissions?
Lowers the Ea, so lowers the temperature needed for the reaction, so less electricity used from combustion of fossil fuels - resulting in less CO2 emissions.
Using the Boltzmann distribution curve explain why temperature increases the rate and describe the new curve.
A greater proportion of molecules have an energy greater than or equal to the Ea - so more frequent collisions. The peak of the curve is lower and shifted right as more particles have higher energies.
Using the Boltzmann distribution curve explain the increased rate of reaction when using a catalyst.
More molecules exceed the new lower Ea so more molecules collide with an energy greater than the Ea, and more frequently. (The peak is identical, it just moves the Ea left)
Definition of equilibrium.
The rate of the forward reaction is equal to the rate of the reverse. The conc of reactants and products remain constant. The system must also remain closed.
How does increasing reactant/product conc affect the position of equilibrium?
Increasing reactant conc shifts it to the right and increasing product conc shifts it to the left.
How does increasing the temp of a forwards exothermic reaction affect the position of equilibrium?
Shifts to the left as it moves in the endothermic direction to counteract and take in the heat.
How does increasing the pressure affect the position of equilibrium?
Shifts it to whichever side has the least particles.
How does a catalyst affect the position of equilibrium?
A catalyst does not change the position, it speeds up the rate of both reactions equally.
What is the formula to calculate the exact position of equilibrium?
Kc = [C]^c x [D]^d
—————–
[A]^a x [B]^b
What does the size of Kc mean?
Kc=1 - equilibrium is in the centre. Kc>1 - equilibrium is to the right. Kc<1 - equilibrium is to the left.
