Rate And Extent Of Chemical Change Flashcards
What are the two equations for rate of reaction ?
Rate of reaction = amount of reactant used/ time
Rate of reaction = amount of product formed/ time
How do you find the rate of a reaction graphically ?
- to measure the rate of reaction, draw tangents to curves and use the slope of the tangent
- calculate the gradient of a tangent to the curve on these graphs as a measure of rate of reaction at a specific time
What are factors which affect the rate of chemical reactions ?
- concentration
- pressure
- surface area
- temperature
- catalysts
Collision theory definition
Chemical reactions can only occur when reacting particles collide with each other and with sufficient energy
Activation energy :
The minimum amount of energy that particles need to react
How does increasing concentration, pressure or surface area of reactants affect rate ?
- increases the frequency of successful collisions
- So increases the rate of reaction
How does increasing the temperature affect the rate of?
- Increases the frequency of collisions
- makes collisions more energetic
- So increases the rate of reaction
What are catalysts and give one example ?
- substances which speed up chemical reactions without being used up during the reaction
- enzymes in biological systems
How do catalysts increases the rate of reaction ?
- decrease activation energy which increases the proportion of particles with energy to react
- provide a different pathway for a chemical reaction that has a lower activation energy
Give an example of a reversible reaction ?
Haber process
Hydrogen + nitrogen = ammonia
If a reversible reaction is exothermic what will it be the other way around?
Endothermic
What is equilibrium and what type of system does it need to occur ?
When the reactions occur at exactly the same rate in each direction, Closed system
What is Le Chateliers principle ?
If dynamic equilibrium is disrupted by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish equilibrium
What will happen if concentration of reactants or products is increased in a system in equilibrium
Concentration of reactants increased :
- position of equilibrium shifts towards products so more product is produced until equilibrium is reached again
Concentration of products is increased :
- position of equilibrium shifts towards reactants so more reactant is produced until equilibrium is reached again
What is the effect of temperature changes in equilibrium?
If temperature is increased :
- equilibrium moves in the direction of the endothermic reaction(if forwards reaction is endothermic equilibrium shifts right to produce more product)
If temperature is decreased :
- equilibrium moves in the direction of the exothermic reaction
What effect would an increase in temperature have on equilibrium in a forwards exothermic vs endothermic reaction?
Exothermic : decrease yield of reaction
Endothermic : increase yield of reaction
What effect would an decrease in temperature have on equilibrium in a forwards exothermic vs endothermic reaction?
Exothermic : increase yield of reaction
Endothermic : decrease yield of reaction
What is the effect of change in pressure on equilibrium ?
If increased pressure : equilibrium shifts to side of equation with fewer moles mass
If decreased pressure : equilibrium will shift to side of equation with more moles of gas
What effect would an increase of pressure have on equilibrium on a larger volume of gas vs a smaller volume of gas ?
Larger volume of gas : decreased yield
Smaller volume of gas : increased yield of reaction
What effect would an decrease of pressure have on equilibrium on a larger volume of gas vs a smaller volume of gas ?
Larger volume of gas : increased yield
Smaller volume of gas : decreased yield
