reversible reactions and equilibria (topic 6) Flashcards
what will the student observe when the anhydrous cobalt chloride is mixed with water (1)
colour will change from blue to pink
the forward reaction is exothermic, explain the effect of increasing the temperature of reaction on the yield of hydrated cobalt chloride (2)
- increasing the temperature favours the endothermic reaction
- yield of hydrated cobalt chloride will decrease
methanol (CH3OH) is produced by reacting carbon monoxide with hydrogen, write a balanced chemical equation for this reversible reaction
calculate how many moles of hydrogen are required to completely react with 5x10^3 moles of carbon monoxide
in industry the process is carried out at a pressure of 100 atmospheres, explain what happens if the reaction is carried out at a lower pressure than this (3)
- high pressures favour the side with fewer particles or low pressure favours the side with a greater number of particles
- at a lower pressure than 100 atmospheres, dynamic equilibrium will shift to the left or shift towards the reactants side
- because there will be fewer collisions per unit time
- because there are fewer molecules per unit volume
a catalyst can be used in the production of methanol from carbon monoxide and hydrogen, explain the role of the catalyst in this reaction (4)
- increases the rate of reaction
- by providing an alternative reaction pathway
- which has a lower activation energy
- without changing the products produced or without getting used up in the reaction
- increasing yield of methanol
state the chemical formula of ethanol
describe the effect of increasing the temperature on the rate of reaction and the percentage yield of ethanol (4)
- higher rate of reaction
- particles have more energy
- greater number of successful collisions
~~~~~~~~~~ - increasing temperature favours the endothermic reverse reaction
- percentage yield of ethanol will be reduced
explain the effect of using a high pressure on the rate of reaction and the percentage yield of ethanol (4)
- rate of reaction will increase
- because there will be a greater number of particles per unit volume
- resulting in a greater number of collisions per unit time
- more collisions will exceed the activation energy or greater number of successful collisions
~~~~~~~~~~ - increasing pressure favours the side of the reaction with fewer particles
- therefore a higher percentage yield of ethanol
- dynamic equilibrium will shift to the product side
- because there are fewer particles on the product side
write a balanced chemical equation for the reversible reaction between methane and steam to produce carbon monoxide and hydrogen
the reaction has a ΔH value of + 206 kJ/mol, explain what this means (2)
- the reaction is endothermic
- the energy required to break the reactants bonds is 206 kJ/mol higher than the energy released by forming the products’ bonds
the reaction is usually completed at 700°C and 5 atmospheres, state the effect on the change of yield of hydrogen at equilibrium if the pressure is decreased to 2 atmospheres (1)
equilibrium shifts in favour of hydrogen production
explain what happens to the dynamic equilibrium when the temperature is halved (4)
- lower temperatures favour the exothermic reaction
- so the reverse reaction is favoured
- particles will have less energy or particles will travel more slowly
- therefore there will be fewer successful collisions per unit time or fewer collisions exceeding the activation energy
which of the following would not shift the dynamic equilibrium to the right
- increasing pressure
- decreasing temperature
- increasing temperature
increasing temperature
write a balanced chemical equation for the reversible reaction between hydrogen (H2) and iodine (I2) to form hydrogen iodide (HI)
draw a reaction profile to show the forward reaction between hydrogen and iodine to form hydrogen iodide, enthalpy change for the reaction ΔH = -9.48 kJ/mol
(2)
- particles of ammonia must travel at a different speed to the hydrochloric acid
- particles of ammonia must travel faster as they have travelled further in the tube
explain how increasing the pressure would change the yield of ammonium chloride (3)
- increasing pressure favours the direction with fewer moles
- increasing the pressure will increase the yield of ammonium chloride
- because there will be more reacting particles per unit volume
- resulting in more successful collisions or more frequent collisions exceeding the activation energy
- CH4(g) + H2O(g) ⇋ CO(g) + 3H2(g)
- ΔH = 160.5 kJ/mol
(4)
- initially the rate of oxygen produced is high
- as shown by a steep line OR high initial gradient
- as time increases, the rate decreases
- as shown by the line becoming less steep or the gradient decreases
- oxygen stops being produced around 12 minutes into the experiment
(4)
state the rate of oxygen production at 15 minutes
0 cm3/minute
