Module 3 Section 2 - Catalysts + Reaction Rates Flashcards
What is a catalyst?
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction.
Example of a catalyst in industry?
An iron catalyst in used in the Haber process to make ammonia.
How do catalysts change enthalpy profile diagrams?
As the activation energy is lower, the peak is lower
How do catalysts affect Boltzmann distribution curve?
The activation energy moves back. A greater proportion of particles exceed the activation energy meaning more successful collisions are likely to occur.
What is a heterogenous catalyst?
A heterogenous catalyst is one that is in a different phase from the reactants ie in a different state. For example in the Haber process, the reactants are gases but solid iron is used for the catalyst
How do heterogenous catalysts work?
The reactions happens on the surface of the heterogenous catalyst. Therefore, Increasing the surface area of the catalyst increases the number of molecules that can react as the same time, increasing the rate of reaction.
What are homogenous catalysts?
Homogenous catalysts are in the same physical state as the reactants.usually a homogenous catalysts is an aqueous catalyst for a reaction between two aqueous solutions.
How do homogenous catalysts work?
They work by forming an intermediate species. The reactants combine with the catalyst to make an intermediate species, which then reacts to form the products and reform the catalyst.
how can catalysts change the properties of a product?
When Polyethene is made without a catalysts it is less dense and less rigid. When made with a catalyst, it is more dense and rigid and has a higher melting point.
How are catalysts good for environmental sustainability
1) using catalysts means lower temperatures and pressures can be used. So energy is saved, meaning less CO2 is released, and fossil fuel reserves are preserved. Catalysts can also reduce waste by allowing a different reaction to be used with better atom economy. An example is ibuprofen. When using a catalyst atom economy jumps from 32 to 77%.
2) catalytic converters on cars are made from alloys of platinum, palladium and rhodium. They reduce the pollution released into the atmosphere by speeding up the reaction.
2CO + 2NO -> 2CO2 + N2
What is reaction rate?
The rate at which a product is formed or a reactant is used up
What is the formula for rate of reaction
Amount of product formed or reactant used / time
What are the two ways to investigate reaction rates?
1) Change in mass
2) Volume of gas given off
How to find reaction rate from change in mass?
1) weigh initial mass
2) at regular intervals, take mass measurements
3) make a table with mass and time columns
4) the reaction is finished when the reading on the mass balance stops decreasing.
5) this method is accurate but releases gas into the room which can be dangerous is gas is toxic or flammable
How to find reaction rate from volume of gas given off?
1) you can use gas syringe to measure the volume of product formed
2) collect the gas formed
3) reaction is over when during no longer moves
4) this is accurate however vigorous reactions can blow the plunger out of the syringe
