Worksheet: Tests for Transition Metals

In this worksheet, we will practice identifying transition metal complexes based on their flame tests and interactions with sodium hydroxide and ammonia.

Q1:

When dissolved in water, the chloride of a first-row transition metal X reacts with dilute ammonia to form a pale green solid and with concentrated ammonia to form a blue solution. What is the identity of the element X?

  • ANi
  • BCo
  • CFe
  • DCr
  • ECu

Q2:

When dissolved in water, which of the following transition metal chlorides does not react with sodium carbonate to produce a blue or green precipitate?

  • ACoCl2
  • BNiCl2
  • CCuCl2
  • DFeCl2
  • ECrCl3

Q3:

When a reagent X is added to a strongly basic solution of chromium(III) nitrate, a yellow solution is produced.

What color is the original solution?

  • AYellow
  • BGreen
  • CPink
  • DOrange
  • EViolet

Which species produces the yellow color of the final solution?

  • ACrO42
  • BCrO272
  • CCrO252
  • DHCrO4
  • EHCrO22

Which of the following is a possible molecular formula for the reagent X?

  • AKMnO4
  • BZn
  • CNH3
  • DHSO24
  • EHO22

What is the oxidation state of chromium in the final yellow solution?

  • A+4
  • B+2
  • C+6
  • D+3
  • E+7

Q4:

At pH 3, a dilute aqueous solution of iron(III) chloride is yellow in color.

Which species is mostly responsible for the color of this solution?

  • A[FeCl]4
  • B[Fe(HO)OH]252+
  • C[Fe(HO)(OH)]242+
  • D[Fe(HO)]262+
  • E[Fe(HO)Cl]242+

What change is observed if concentrated acid is added to this solution?

  • AA green solution is produced.
  • BA green solid precipitates.
  • CA lilac solid precipitates.
  • DAn orange solid precipitates.
  • EA lilac solution is produced.

If added to this solution, which of the following reagents would not react to form a solid material?

  • ASodium hydroxide
  • BAmmonia
  • CSodium thiocyanate
  • DSodium sulfate
  • ESodium carbonate

As the pH of the solution increases, what happens to the geometry of the transition metal complex and the frequency of the light absorbed?

  • AThe complex changes from octahedral to tetrahedral and lower-frequency light is absorbed.
  • BThe geometry of the complex is unchanged and lower-frequency light is absorbed.
  • CThe geometry of the complex is unchanged and higher-frequency light is absorbed.
  • DThe complex changes from tetrahedral to octahedral and lower-frequency light is absorbed.
  • EThe complex changes from octahedral to tetrahedral and higher-frequency light is absorbed.

Q5:

When a complex of vanadium reacts with zinc under acidic aqueous conditions, the color of the solution changes from blue to purple.

What is the structure of the original complex?

  • A[V(HO)]262+
  • B[VO(HO)]252+
  • C[V(HO)]263+
  • D[VO(HO)]2242+
  • E[VO(HO)]224+

What is the oxidation state of vanadium in the final complex?

  • A+5
  • B+3
  • C+6
  • D+4
  • E+2

If the original vanadium complex is instead oxidized, what is the color of the resulting solution?

  • AYellow
  • BGreen
  • CPurple
  • DBlue
  • EColorless

Q6:

Many cobalt(II) salts dissolve in water to produce the colored complex ion [Co(HO)]262+. Adding dilute ammonia to this solution produces a colored precipitate, which redissolves in the presence of excess ammonia.

What color is an aqueous solution of the [Co(HO)]262+ ion?

  • AYellow
  • BBlue
  • CPink
  • DGreen
  • ERed

Draw an energy level diagram illustrating the arrangement of valence d electrons in the [Co(HO)]262+ ion.

  • A
  • B
  • C
  • D
  • E

What is the formula of the major solid product when aqueous [Co(HO)]262+ ions react with dilute ammonia?

  • A[Co(HO)(NH)]2432
  • B[Co(NH)(OH)]342
  • C[Co(NH)(OH)]333
  • D[Co(HO)(OH)]242
  • E[Co(HO)(NH)]2333

When excess ammonia is added to aqueous [Co(HO)]262+ ions, the resulting complex ion has a 2+ charge. How does this reaction affect the geometry of the complex ions and the frequency of the light it absorbs?

  • AThe complex converts from octahedral to tetrahedral and lower-frequency light is absorbed.
  • BThe complex converts from tetrahedral to octahedral and lower-frequency light is absorbed.
  • CThe complex converts from octahedral to tetrahedral and higher-frequency light is absorbed.
  • DThe geometry of the complex is unchanged and higher-frequency light is absorbed.
  • EThe geometry of the complex is unchanged and lower-frequency light is absorbed.

Q7:

Which of the following coordination complexes absorbs light of the shortest wavelength?

  • A[FeCl]63
  • B[FeF]63
  • C[Fe(NH)]363+
  • D[Fe(HO)]263+
  • E[Fe(CN)]63

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