chemistry c5 Flashcards
What is the rate of reaction?
amount of reactant used or product formed
—————————————————
time taken or rate of reaction
How do you measure the volume of a gas produced?
Using an upside-down measuring cylinder in water or a gas syringe
What is the equation for the reaction between magnesium and dilute hydrochloric acid?
Mg(s) + 2HCl(aq) → MgCl(aq) + H₂(g)
What steps should you follow to measure the rate of hydrogen production in the magnesium and hydrochloric acid reaction?
- Place dilute hydrochloric acid in a conical flask connected to a gas syringe
- Add magnesium ribbon and stopper the flask
- Start a stop clock and record the time and volume of hydrogen at regular intervals
- Draw a line graph of the results
What should you do before adding the stopper to the conical flask in the hydrogen production investigation?
Push the plunger of the gas syringe all the way in to start at a reading of 0 cm³
Fill in the blank: The rate of reaction is a measure of how quickly ________ are used or ________ are formed.
[reactants], [products]
True or False: A reaction with a high rate will form a large amount of product in a short time.
True
how to calculate mean rate of reaction between a certain time?
calculate the gradient of curve
why do reactions go faster at higher temperatures?
- particles have more energy so they move faster
- particles collide more often leading to successful collisions
how to investigate effect of temperature? (practical)
- put a cross on a paper and put beaker over it
- mix reactants in beaker
- look through the mixture and use a stopwatch to record the time it takes for cross to disappear
the rate of reaction is what to the reaction time?
inversely propertional
why do reactions go faster at higher concentrations?
more particles (crowded) so more collisions which lead to more successful collisions
why do reactions go faster at higher pressure?
particles are more crowded so collide more often leading to more successful collisions
why do reactions go faster with powders?
- more particles available for collisions and collide more often
- increased surface area so more surface to react with
what are catalysts?
substance that speed up rate of reaction without changing but is unchanged at end of reaction
what is a biological catalyst?
enzymes
how do catalysts work?
provide an alternative pathway that lowers the activation energy
what are reversible reactions?
products can be changed back into reactants
what is dynamic equilibrium?
rate of forwards reaction equals rate of backwards reaction
concentrations remain constant
what is the equilibrium position when concentration is greater on reactants side?
left (reactants)
what happens when pressure is changed?
if pressure increased, equilibrium position moves in direction with fewest moles
what happens if temperature is changed?
- if temperature increases, equilibrium position moves in direction of endothermic change
- decide if forward reaction is ex/endothermic (+ or -)
what is the equilibrium yield?
amount of desired product present in a reaction at equilibrium
what is le chateliers principle?
‘when a change is made to a reaction at equilibrium, the position of equilibrium moves to oppose the change’
