Acids and Bases
What is the Bronsted-Lowry definition of an acid?
A substance that donates a proton (H+)
At equilibrium, what is the relationship between Keq and Q
they are equal
Write the equilibrium constant expressions for this reaction: 2NO(g)+O2(g)⇌2NO2(g)
K=([NO2]^2)/([NO]^2*[O2])
Give a factor that can shift a reaction's equilibrium position.
Temperature, concentration, volume, heat , etc.
What will happen if you increase the concentration of reactants in a system at equilibrium?
Will shift toward the products (right)
What is the pH for a 0.05M solution of hydrochloric acid
1.3
Write the following as an equilibrium P4(s) + 6Cl2(g) ⇌ 4PCl3(l)
1/([Cl2]^6)
N2 + 3H2 ⇌ 2NH3
An increase in pressure would cause the reaction to shift in which direction?
Right (Fewer moles)
What would happen if the following reaction were heated? H2(g) + I2(g) ⇌ 2HI(g) + heat
shift to reactants / left
What would happen if you removed chlorine gas?
P4(s) + 6Cl2(g) ⇌ 4PCl3(l)
shift to the reactants / left
Calculate the pH of a resulting mixture when 200mL 2.0M NaOH is added to 500 mL 1.0M HCl
pH = 0.84
Explain the concept of a heterogeneous equilibrium with an example
An equilibrium involving reactants and products in different physical states, such as a solid and a gas. Examples can vary.
Given the reaction below, what is the equilibrium constant if the concentrations are [N2] = 3.0x10-2M , [H2] = 3.7x10-2M and [NH3] = 1.6x10-2M. Which side is favored?
2NH3(g) ⇌ N2(g) + 3H2(g)
0.0059 or 5.9x10-3 - reactants favored
What would increasing the pressure do to the following reaction:
CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g)
Shift to the reactants / left
H2O (g) + C (s) ⇄ H2 (g) + CO (g)
([H2]*[CO])/[H2O]
Given the acid dissociation constant Kw, 3.2x10-8, calculate the concentration of H+ of a 0.14M solution of HOCl (weak acid).
[H+]=6.7x10-5 M
Kc for the equilibrium reaction is determined at two different temperatures.
At 850°C, Kc = 1.1.
At 1700°C, Kc = 4.9.
Based on these values, is this reaction likely to be exothermic or endothermic.
Endothermic
(Higher temperature led to more products)
0.0206 M CH3OH, 0.120 M carbon monoxide, and 0.282 M hydrogen at 500 K. Calculate the equilibrium constant at this temperature.
CO (g) + H2 (g) ⇌ CH3OH (g)
Does this favor the reactants or the products?
Products (Kc = 2.16)
How does a decrease in temperature affect the position of equilibrium in an exothermic reaction
Will shift to the right to absorb the excess heat
Describe the role of a catalyst in a chemical reaction at equilibrium
A catalyst increases the rate at which equilibrium is reached by lowering the activation energy but does not affect the position of equilibrium
The dissociation of acetic acid, CH3COOH, has an equilibrium constant at 25°C of 1.8 x 10-5. The reaction is
CH3COOH (aq) ⇌ CH3COO-(aq) + H+(aq)
If the equilibrium concentration of CH3COOH is 0.46 moles in 0.500 L of water and that of CH3COO- is 8.1 x 10-3 moles in the same 0.500 L, calculate [H+] for the reaction.
[H+ ] = 1.0 x 10-3 M
If the Keq of the following reaction is 7.7x10-15. Is the reaction at equilibrium if [CO] = 0.034M, [CO2] = 3.6x10-17M (show value). If not which way will it shift?
2CO(g) ⇌ C(s) + CO2(g)
3.11x10-14 reactants / left
A mixture of 9.22 moles of A, 10.11 moles of B, and 27.83 moles of C is placed in a one-liter container at a certain temperature. At equilibrium, the number of moles of B is 18.32. Calculate the equilibrium constant for the reaction: A (g) + 2B (g) ⇌ 3C (g)
Kc = 0.832
In a chemical reaction at equilibrium, if the concentration of both reactants and products is initially high and the pressure of the container is suddenly increased, predict the direction of the shift in equilibrium
The equilibrium will shift towards the side with fewer moles of gas to counteract the increase in pressure.
What is the conjugate base of HCO3-
CO32-