and
How will the rate of the reverse reaction be affected by:
a decrease in temperature?
the addition of a catalyst?
the addition of more NO gas?
The rate of the forward reaction will increase since it is the forward reaction that is exothermix and therefore
produces energy to balance the loss of energy from the decrease in temperature. The rate of the reverse reaction will decrease.
The rate of the reverse and the forward reaction will increase.
The rate of the reverse reaction
will increase so that the extra NO gas is converted into NO
gas.
Write a balanced equation for the exothermic reaction between
Zn(s) and HCl.
Name 3 ways to increase the reaction rate between hydrochloric
acid and zinc metal.
A catalyst could be added, the zinc solid could be ground
into a fine powder to increase its surface area, the HClconcentration could be increased or the reaction temperature
could be increased.
The following reaction reaches equilibrium in a closed container:
The pressure of the system is increased by decreasing the volume of the container. How will the number of moles and the concentration of the CO
(g) have changed when a new equilibrium is reached at the same temperature?
moles of CO
[CO
]
A
decreased
decreased
B
increased
increased
C
decreased
stays the same
D
decreased
increased
(IEB Paper 2, 2003)
The following reaction has reached equilibrium in a closed container:
>0
The pressure of the system is then decreased by increasing the volume of the container. How will the concentration of the H
(g) and the value of K
be affected when the new equilibrium is established? Assume that the temperature of the system remains unchanged.
[H
]
K
A
increases
increases
B
increases
unchanged
C
unchanged
unchanged
D
decreases
unchanged
(IEB Paper 2, 2004)
During a classroom experiment copper metal reacts with concentrated nitric acid to produce NO
gas, which is collected in a gas syringe. When enough gas has collected in the syringe, the delivery tube is clamped so that no gas can escape. The brown NO
gas collected reaches an equilibrium with colourless N
O
gas as represented by the following equation:
Once this equilibrium has been established, there are 0.01 moles of NO
gas and 0.03 moles of N
O
gas present in the syringe.
A learner, noticing that the colour of the gas mixture in the syringe is no longer changing, comments that all chemical reactions in the syringe must have stopped. Is this assumption correct? Explain.
The gas in the syringe is cooled. The volume of the gas is kept constant during the cooling process. Will the gas be lighter or darker at the lower temperature? Explain your answer.
The volume of the syringe is now reduced to 75 cm
by pushing the plunger in and holding it in the new position. There are 0.032 moles of N
O
gas present once the equilibrium has been re-established at the reduced volume (75 cm
). Calculate the value of the equilibrium constant for this equilibrium.
(IEB Paper 2, 2004)
Consider the following reaction, which takes place in a closed container:
H
0
If you wanted to increase the rate of the reaction, which of the following would you do?
decrease the concentration of B
decrease the temperature of A
grind A into a fine powder
decrease the pressure
(IEB Paper 2, 2002)
Gases X and Y are pumped into a 2 dm
container. When the container is sealed, 4 moles of gas X and 4 moles of gas Y are present. The following equilibrium is established:
The graph below shows the number of moles of gas X and gas X
Y
that are present from the time the container is sealed.
How many moles of gas X
Y
are formed by the time the reaction reaches equilibrium at 30 seconds?
Calculate the value of the equilibrium constant at t = 50 s.
At 70 s the temperature is increased. Is the forward reaction endothermic or exothermic? Explain in terms of Le Chatelier's Principle.
How will this increase in temperature affect the value of the equilibrium constant?