Target: 10 Questions in 10 minutes

An IB Chemistry data booklet is helpful

1. Identify the most suitable indicator for the titration with the following pH curve, using table 18 of the IB Chemistry data booklet:

titration graph Q4
  • A.   Methyl orange
  • B.   Bromothymol blue
  • C.   Phenolphthalein
  • D.   Bromocresol green
2. A buffer is composed of equal concentrations of NH3 and NH4Cl. Which of the following statements is true for this buffer?
  • A.   When an acid is added into the buffer, the H+ will react with the NH4+ in the buffer.
  • B.   When an acid is added into the buffer, the H+ will react with the Cl- in the buffer
  • C.   When an alkali is added into the buffer, the OH- will react with the NH4+ in the buffer.
  • D.   When an alkali is added into the buffer, the OH- will react with the NH3 in the buffer.
3. Which of the following, when mixed in equal volumes, will make a buffer solution?
  • A.   0.2 mol dm-3 CH3COOH and 0.1 mol dm-3 NaOH
  • B.   0.2 mol dm-3 HCl and 0.1 mol dm-3 NH4Cl
  • C.   0.1 mol dm-3 CH3COOH and 0.2mol dm-3 NaOH
  • D.   0.1 mol dm-3 HCl and 0.2 mol dm-3 NH4Cl

4. Which part of the pH curve below shows the buffer region of a weak base-strong acid titration?

titration graph Q4

5.  Which indicator is suitable for a titration between 0.5 mol dm-3 HCl and 0.5 mol dm-3 KOH?

Use table 18 of the IB Chemistry data booklet.

I. Methyl red
II. Bromothymol blue
III. Phenol red
 
  • A.   I only
  • B.   I and II only
  • C.   II and III only
  • D.   I, II and III
6. Methyl red is a weakly acidic indicator. It can be represented by the formula HIn and its pKa = 5.1. It is red in acidic pH and yellow in alkaline pH. When it dissociates in water, it exists as In-.

Which of the following statement is true for methyl red?

  • A.   HIn is yellow in colour
  • B.   In- is yellow in colour
  • C.   Methyl red can be used as an indicator for a strong base-weak acid titration
  • D.   Methyl red changes colour around pH = 10.2

7. Which solution(s) will produce a buffer solution when added to 50 cm3 of 0.5 mol dm-3 CH3COOH?

I. 25 cm3 of 0.5 mol dm-3 NaOH
II. 25 cm3 of 0.5 mol dm-3 CH3COONa
III. 25 cm3 of 0.5 mol dm-3 NaHCO3
  • A.   I only
  • B.   I and II only
  • C.   II and III only
  • D.   I, II and III
8. What is the pH of a buffer solution made by mixing 25 cm3 of 0.2 mol dm-3 NH3 and 50 cm3 of 0.2 mol dm-3 NH4Cl? The pKb of NH3 = 4.75.
  • A.  9.25
  • B.  8.95
  • C.  5.05
  • D.  4.45
9. Calculate the pH of the solution formed when 0.243 g of pure magnesium powder is added into 100 cm3 of 0.5 mol dm-3 CH3COOH. The pKa of CH3COOH = 4.76.
  • A.  9.84
  • B.  7.00
  • C.  4.76
  • D.  4.58
10. Calculate the volume of 0.200 mol dm-3 sodium propanoate that is required to mix with 50 cm3 of 0.200 mol dm-3 propanoic acid, in order to produce a buffer of pH = 5.00. The pKa for propanoic acid is 4.87.
  • A.   50 cm3
  • B.   67 cm3
  • C.   100 cm3
  • D.   133 cm3