Quelpr
1 markThe Mole Concept

CAPE Chemistry Unit 1 · May/June 2024 · Paper 2 · Question 1(f)(i)

Potassium nitrate decomposes on heating: 2 KNO3(s) -> 2 KNO2(s) + O2(g). A sample of KNO3 weighing 6.20 g (Sample A) was partially decomposed. The residue was dissolved in water to make 1 dm^3 of solution. A 25.0 cm^3 aliquot was acidified and titrated with 0.02 mol dm^-3 KMnO4, requiring an average titre of 27.50 cm^3.

Calculate the number of moles of potassium manganate(VII) used in the titration.

The mark scheme is shown once you've answered.

Practise this question

Other parts of this question

  1. 1(a)Name the series of lines produced by these electron transitions.[1 mark]
  2. 1(b)Draw diagrams (including the axes) to show the shapes of the s and p orbitals.[2 marks]
  3. 1(c)State what is meant by the term 'hybridization'.[2 marks]
  4. 1(d)Benzene exhibits resonance structures. Explain what is meant by 'resonance'.[2 marks]
  5. 1(e)(i)State THREE criteria used in the valence shell electron pair repulsion (VSEPR) theory to determine the shapes of molecules and ions.[3 marks]
  6. 1(e)(ii)a)Use the criteria in (e)(i) to determine the shape and bond angles in the beryllium chloride molecule.[2 marks]
  7. 1(e)(ii)b)Use the criteria in (e)(i) to determine the shape and bond angles in the methyl anion, CH3^-.[2 marks]
  8. 1(e)(iii)Draw a diagram to show the shape of the methyl anion, CH3^-.[1 mark]
  9. 1(f)(ii)Using the equation 2 MnO4^-(aq) + 5 NO2^-(aq) + 6 H^+(aq) -> 2 Mn^2+(aq) + 5 NO3^-(aq) + 3 H2O(l), deduce the number of moles of KNO2 present in the titre…[1 mark]
  10. 1(f)(iii)Calculate the number of moles of KNO2 that was present in the residue from the decomposition of Sample A.[1 mark]
  11. 1(f)(iv)Calculate the mass of KNO2 present in the residue from Sample A.[2 marks]
  12. 1(f)(v)Using the equation for the decomposition of KNO3, determine the mass of KNO2 formed if 6.20 g KNO3 were completely decomposed.[3 marks]
  13. 1(f)(vi)Using the results from (f)(iv) and (v), calculate the percentage of KNO2 formed.[2 marks]
  14. 1(f)(vii)Outline the experimental steps taken in the laboratory to prepare the 0.02 mol dm^-3 potassium manganate(VII) solution used for this titration.[5 marks]

More practice: the rest of this paper · more The Mole Concept questions · all CAPE Chemistry Unit 1 past papers