Formation of coloured ions Quiz
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5 questions, one answer each
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1. Which change would NOT alter the colour of a solution of [Co(H₂O)₆]²⁺?
- A. Adding concentrated hydrochloric acid
- B. Adding excess ammonia to replace water ligands
- C. Oxidising Co²⁺ to Co³⁺
- D. Using a larger beaker
2. A solution absorbs light of wavelength 400 nm. Another absorbs 700 nm. Which has the larger ΔE?
- A. The 700 nm solution
- B. The 400 nm solution
- C. They are equal
- D. It depends on the concentration
3. What is ΔE in J for light of wavelength 500 nm? (h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹)
- A. 3.98 × 10⁻¹⁹ J
- B. 3.98 × 10⁻²⁸ J
- C. 1.66 × 10⁻²⁷ J
- D. 2.51 × 10⁻²⁰ J
4. Why is a solution of Cu⁺ ions colourless?
- A. Cu⁺ has no electrons
- B. Its d sub-level is full, so no d electron can be promoted
- C. Copper(I) compounds always absorb ultraviolet light
- D. The solution is too dilute
5. A colorimeter gives an absorbance of 0.30 for a 0.040 mol dm⁻³ standard. A diluted sample (diluted from 5.0 cm³ to 25.0 cm³) gives an absorbance of 0.45. What is the concentration of the original sample?
- A. 0.060 mol dm⁻³
- B. 0.30 mol dm⁻³
- C. 0.012 mol dm⁻³
- D. 0.15 mol dm⁻³