Year 12 Chemistry Tutorial 9.3.D – Acid Behaviour Module 9.3 – The Acidic Environment Topic 9.3.D – Acid Behaviour Name 1.
Date Outline Lavoisier’s theory of acids citing an example and identifying its limitations. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 2.
Outline the Davy theory of acids, citing an example and identifying its limitations. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 3.
Write an equation to show: (a) nitric acid acting as an Arrhenius acid. …………………………………………………………………………………………………………………………………………………………………………………… (b) calcium hydroxide acting as an Arrhenius base. …………………………………………………………………………………………………………………………………………………………………………………… 4.
Use the reaction between ammonia gas and hydrogen chloride gas to account for the limitations of the Arrhenius theory of acids and bases. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 5.
Use the reaction in Question 4 to explain aspects of the Bronsted-­‐Lowry theory of acids and bases. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 6.
Use the theories of acids and bases developed by Lavoisier, Davy, Arrhenius and Bronsted-­‐Lowry to show that dihydrogen sulfate was classified as an acid in each case. Support your answer with equations where appropriate. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 7.
Identify the conjugate acid-­‐base pairs in each of the following reactions: +
–
(a) NH3 (g) + H2O (l) ⇔ NH4 (aq) + OH (aq) …………………………………………………………………………………………………………………………………………………………………………………… –
–
(b) HNO3 (aq) + OH (aq) ⇔ NO3 (aq) + H2O (l) …………………………………………………………………………………………………………………………………………………………………………………… +
–
(c) H2O (l) + H2O (l) ⇔ H3O (aq) + OH (aq) …………………………………………………………………………………………………………………………………………………………………………………… –
2–
+
(d) HSO3 (aq) + H2O (l) ⇔ SO3 (aq) + H3O (aq) …………………………………………………………………………………………………………………………………………………………………………………… Page 2 8.
The following substances behave as bases in aqueous solution. Write an equation for each one to show how its conjugate acid is formed. –
(a) OH (aq) …………………………………………………………………………………………………………………………………………………………………………………… –
(b) HSO3 (aq) …………………………………………………………………………………………………………………………………………………………………………………… (c) H2O (l) …………………………………………………………………………………………………………………………………………………………………………………… 2– (d) CO3 (aq) …………………………………………………………………………………………………………………………………………………………………………………… – (e) HCO3 (aq) …………………………………………………………………………………………………………………………………………………………………………………… 9.
The following substances behave as acids in some circumstances. Write an equation for each one to show how its conjugate base is formed. (a) H2S (aq) …………………………………………………………………………………………………………………………………………………………………………………… –
(b) HSO3 (aq) …………………………………………………………………………………………………………………………………………………………………………………… (c) H2O (l) …………………………………………………………………………………………………………………………………………………………………………………… (d) HCOOH (aq) …………………………………………………………………………………………………………………………………………………………………………………… 10. Use your knowledge of Bronsted-­‐Lowry theory to identify the base in each reaction: –
+
2–
(a) HSO4 + HNO3 ⇔ H2NO3 + SO4 …………………………………………………………………………………………………………………………………………………………………………………… –
–
2–
(b) H2PO4 + HCO3 ⇔ HPO4 + H2O + CO2 …………………………………………………………………………………………………………………………………………………………………………………… +
–
(c) CH3COOH + HNO3 ⇔ CH3COOH2 + NO3 …………………………………………………………………………………………………………………………………………………………………………………… –
+
(d) HBr + HCl ⇔ Br + H2Cl …………………………………………………………………………………………………………………………………………………………………………………… Page 3 11. An aqueous solution of sodium nitrate will have a neutral pH while an aqueous solution of sodium ethanoate will not. Account for this difference in pH using chemical equations to support your answer. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 12. Predict the pH of an aqueous solution of ammonium chloride and justify your answer. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 13. Ammonium fluoride has a slightly basic pH even though it is derived from a weak acid and a weak base. Explain why this is the case. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… 14. An amphiprotic species is one that can act as either an acid or a base under different conditions. Identify such a species and write chemical equations to show it acting as an acid and a base. …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………… Page 4 15. The pH of human blood is maintained at about 7.4 by various buffers systems. One of the most important of these is the -­‐
2-­‐
dihydrogen phosphate/hydrogen phosphate (H2PO4 /HPO4 ) equilibrium. (a) Write an equation for this equilibrium. …………………………………………………………………………………………………………………………………………………………………………………… (b) Explain how this buffer solution could resist a change in pH if an acid or base was added to the system. …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………… Page 5