Topic 8 and 18

What is the formula of the conjugate base of the hydrogenphosphate ion, HPO₄^2–? 

• H₂PO₄^– 
• H3PO₄
• HPO₄^– 
• PO₄^3– 

An example of a strong acid solution is perchloric acid, HClO₄, in water. Which statement is correct for this solution? 

• HClO₄ is completely dissociated in the solution. 
• HClO₄ exists mainly as molecules in the solution. 
• The solution reacts only with strong bases. 
• The solution has a pH value greater than 7. 

What is the approximate pH of a 0.01 mol dm^–3 ammonia solution? 

• 2 
• More than 2 but less than 7 
• More than 7 but less than 12 
• 12 

When equal volumes of four 0.1 mol dm^–3 solutions are arranged in order of increasing pH (lowest pH first), what is the correct order? 

• CH₃COOH < HNO₃ < CH₃CH₂NH₂ < KOH 
• HNO₃ < CH₃COOH < CH₃CH₂NH₂ < KOH 
• CH₃CH₂NH₂ < HNO₃ < CH₃COOH < KOH 
• KOH < CH₃CH₂NH₂ < CH₃COOH < HNO₃ 

A solution of acid A has a pH of 1 and a solution of acid B has a pH of 2. Which statement must be correct? 

• Acid A is stronger than acid B 
• [A] > [B] 
• The concentration of H⁺ ions in A is higher than in B 
• The concentration of H⁺ ions in B is twice the concentration of H⁺ ions in A 

Which species can act as a Lewis acid? 

• BF₃ 
• OH^– 
• H₂O 
• NH₃ 

Which indicator would be the most appropriate for titrating aqueous ethylamine, CH₃CH₂NH₂, with nitric acid, HNO₃? 

• Bromophenol blue (pKa = 4.1) 
• Bromothymol blue (pKa = 7.3) 
• Phenol red (pKa = 8.0) 
• Thymolphthalein (pKa = 10.0) 

Ammonia acts as a weak base when it reacts with water. What is the K_b expression for this reaction? 

• A.
• B.
• C.
• D.

Equal volumes and concentrations of hydrochloric acid and ethanoic acid are titrated with sodium hydroxide solutions of the same concentration. Which statement is correct? 

• The initial pH values of both acids are equal. 
• At the equivalence points, the solutions of both titrations have pH values of 7. 
• The same volume of sodium hydroxide is needed to reach the equivalence point. 
• The pH values of both acids increase equally until the equivalence points are reached. 

pKw for water at 10 °C = 14.54. What is the pH of pure water at this temperature? 

• 6.73 
• 7.00 
• 7.27 
• 7.54