Iodic acid and sulfamic acid are monoprotic acids. A 0.100 mol L
Show that neither iodic acid nor sulfamic acid dissociates completely in water, and determine which is the stronger acid. (3 marks)
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Iodic acid and sulfamic acid are monoprotic acids. A 0.100 mol L
Show that neither iodic acid nor sulfamic acid dissociates completely in water, and determine which is the stronger acid. (3 marks)
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→ Calculating the concentration of hydronium ions in solution for a pH of 1.151.
→ As this is less than the concentration of both of the acids, neither acid completely dissociates in water.
→ A smaller concentration of iodic acid (0.100 mol/L compared to 0.120 mol/L sulfamic acid) produces the same pH level. Iodic acid must have a greater extent of ionisation compared to sulfamic acid.
→ Therefore iodic acid is a stronger acid than sulfamic acid.
→ Calculating the concentration of hydronium ions in solution for a pH of 1.151.
→ As this is less than the concentration of both of the acids, neither acid completely dissociates in water.
→ A smaller concentration of iodic acid (0.100 mol/L compared to 0.120 mol/L sulfamic acid) produces the same pH level. Iodic acid must have a greater extent of ionisation compared to sulfamic acid.
→ Therefore iodic acid is a stronger acid than sulfamic acid.
Which beaker contains a concentrated strong acid?
→ A concentrated strong acid will have a greater number of molecules per unit volume, and completely dissociate in water.
The graph shows changes in pH for the titrations of equal volumes of solutions of two monoprotic acids, Acid 1 and Acid 2.
Explain the differences between Acid 1 and Acid 2 in terms of their relative strengths and concentrations. (3 marks)
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→ Acid 1 is a strong acid. Its initial pH = 1 and its equivalence point is at pH = 7.
→ Acid 2 is a weaker acid. Its initial pH ~ 2 and its equivalence point is >7.
→ Acid 2 has a higher concentration than Acid 1 as it doesn’t take that much more
→ Acid 1 is a strong acid. Its initial pH = 1 and its equivalence point is at pH = 7.
→ Acid 2 is a weaker acid. Its initial pH ~ 2 and its equivalence point is >7.
→ Acid 2 has a higher concentration than Acid 1 as it doesn’t take that much more
Which diagram represents ionisation of a weak acid?
→ Partial ionisation will result in a solution that contains hydronium, anions and water.
Which combination of equimolar solutions would produce the most basic mixture?
→ Acetic acid
→ When acetic acid reacts with sodium carbonate
→ Sulfuric acid
Which of the following solutions has the highest pH?
By Elimination:
→ Acetic acid is weaker than hydrochloric acid and therefore has a higher pH (eliminate C and D).
→ A more dilute acid has a higher pH (eliminate A).
The effect of concentration on the pH of acrylic acid
Explain the trends in the graph. Include relevant chemical equations in your answer. (4 marks)
→
→ Acrylic acid, on the other hand, is a weak acid that only partially dissociates in water, resulting in a lower concentration of
→ When the concentration of
→ However, when the concentration of acrylic acid decreases by a factor of 10, its pH increases by less than 1.
→ This is due to the change in pH causing the equilibrium to shift right, producing more
→ At very dilute concentrations, the degree of dissociation of acrylic acid approaches 100% and its pH converges closely to that of
→
→ Acrylic acid, on the other hand, is a weak acid that only partially dissociates in water, resulting in a lower concentration of
→ When the concentration of
→ However, when the concentration of acrylic acid decreases by a factor of 10, its pH increases by less than 1.
→ This is due to the change in pH causing the equilibrium to shift right, producing more
→ At very dilute concentrations, the degree of dissociation of acrylic acid approaches 100% and its pH converges closely to that of
An aqueous solution of sodium hydrogen carbonate has a pH greater than 7 .
Which statement best explains this observation?
→
→
→ As a result, this produces
The pH of two aqueous solutions was compared.
Explain why the
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→
→ On the other hand,
→ As
→ Therefore, at the same 0.2M, the
→
→ On the other hand,
→ As
→ Therefore, at the same 0.2M, the
The molar enthalpies of neutralisation of three reactions are given.
Reaction 1:
Reaction 2:
Reaction 3:
Explain why the first two reactions have the same enthalpy value but the third reaction has a different value. (4 marks)
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→ Reaction 1 and reaction 2 are both neutralisation reactions between strong acids and strong bases. These reactions completely ionise in solution when added to water.
→ Both reactions have the same net ionic equation:
→ Therefore, the enthalpy values obtained are the same for both reactions.
→ In reaction 3,
→ As the reaction continues,
→ The bond-breaking is an endothermic process and thus will consume energy to break the bonds. As a result, the overall reaction is less exothermic than reaction 1 and reaction 2.
→ Reaction 1 and reaction 2 are both neutralisation reactions between strong acids and strong bases. These reactions completely ionise in solution when added to water.
→ Both reactions have the same net ionic equation:
→ Therefore, the enthalpy values obtained are the same for both reactions.
→ In reaction 3,
→ As the reaction continues,
→ The bond-breaking is an endothermic process and thus will consume energy to break the bonds. As a result, the overall reaction is less exothermic than reaction 1 and reaction 2.
Methanoic acid reacts with aqueous potassium hydroxide. A salt is produced in this reaction.
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a.
b. Potassium methanoate is a basic salt.
This is because the
a.
b. Potassium methanoate is a basic salt.
This is because the
Which row of the table describes what happens when a solution of a weak acid is diluted? (Assume constant temperature.)
A weak acid has the following equilibrium:
→ The value of
→ When the solution is diluted, water is added. According to Le Chatelier’s Principle, the equilibrium will shift to the right to counteract the change.
→ Thus, the equilibrium will shift to the right and increase the extent of ionisation.