Question 1
What is meant by the term conjugate acid-base pair? find the conjugate acids/base pair for the following species:
HNO2, CN–, HClO4, HSO4–, H2O and F–.
Question 2
Which of the following are Lewis acids or Lewis bases?
PH3, BCl3, HCO3–, AlCl3, HSO4–, SiCl4, NH3, H2O
Question 3
The concentration of hydrogen ion in sparkling water is 5.6 x 10-4 M. What is its pH?
Question 4
The pH of lemon juice is 3.94. Calculate the concetration of the hydrogen ions in it.
Question 5
The ionisation constant of benzoic acid, CH3COOH and HCN at 298K are 3 x 10-8, 1.75 x 10-5 and 4.8 x 10-9 mol dm-3 respectively. Calculate the ionisation constants of the corresponding conjugate base.
Question 6
The ionisation constant of a weak monoprotic acid is 1.5 x 10-10. What is the concentration of the phenolate ion is 0.05 M solution of the acid is present? What will be its degree of ionisation if 0.01M of the monoprotic salt is added?
Question 7
Predict if the solutions of the following salts are neutral, acidic or basic:
NaCl, NaCN, KBr, CH3COONa, NaNO2, NH4Cl
Question 8
The ionic product of water at 310K is 2.7 x 10-14. What is the pH of water at this temperature? Is the solution still neutral?
Question 9
The ionisation constant of CH2ClCOOH is 1.35 x 10-3. What will be the pH of 0.1M acid? What is the pH when 0.1M sodium salt is added to the 0.1M acid solution?
Question 10
Use the following acid ionisation constants to identify the correct decreasing order to base strengths:
HF Ka= 7.2 x 10-4
HNO2 Ka= 4.5 x 10-4
HCN Ka= 6.2 x 10-10
Question 11
i) Pure ethanoic acid has a concentration of 17.54M. 85.5 mL of ethanoic acid was diluted to 250 mL. 26 mL of this diluted solution was further diluted to 800 mL. If the pH of the final solution is 2.74, calculate Ka for acetic acid.
ii) If 13.2g of CH3COONa are added to the 800mL of solution in part (i), what is the resulting pH?
iii) The resulting solution in part (ii) is divided into two 440 mL samples. If 5 mL of 6M HCl are added to one sample, and 7 mL of 4 M NaOH are added to the other, what is the resultant pH in each case?
Question 12
If 0.05 mL of 6 M HCl is added to 400 mL of 10-5 M HCl, what is the resulting pH?
Question 13
What is the pH of a buffer prepared with 0.4M CH3COOH and 0.2M CH3COO–, if the Ka of acetic acid is 1.8 x 10-5?
Question 14
How many grams of the strong base potassium hydroxide (KOH, molar mass = 56.11 g/mole) is required to make 115 mL of solution having pH = 13.52?
Question 15
What is the pH of a 0.3M solution of CH3COONa? The Ka for acetic acid is 1.8 x 10-5?
Question 16
How many grams of the weak acid HF (molar mass = 20.01 g/mole) does it take to prepare 715 mL of a solution that has pH = 2.075?
Question 17
What is the pH of a 0.15M solution of aspirin? The kb for aspirin is 3.16 x 10-11
Question 18
A 0.21 mol dm-3 solution of KOH was added from a burette to 25 cm3of a 0.16 mol dm-3 solution of CH3COOH in a conical flask. Given that the calue of the acid dissociation constant, Ka, for CH3COOH is 1.74 x 10-5 mol dm-3, calculate the pH at 250C of the solution in the conical flask at the following three points:
i) before any KOH had been added;
ii) after 8 cm3 of KOH solution had been added
iii) after 50 cm3 of KOH solution had been added.
Harder questions
Question 19
H2S has a first ionisation energy of 9.1 x 10-8. Calculate the concentration of HS– ion in a 0.1M solution. What will happen to the HS– concentration when 0.1M HCl is added? If the second dissociation constant for H2S is 1.2 x 10-13, calculate the concentration of S2- under both conditions.
Question 20
What is the pH of a 0.4M solution of NaNO2? The pKa for HNO2 is 3.35.