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 ?

  • A C r
  • B N i
  • C C o
  • D C u
  • E F e

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?

  • A C o C l 2
  • B C r C l 3
  • C F e C l 2
  • D N i C l 2
  • E C u C l 2

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?

  • APink
  • BViolet
  • CYellow
  • DGreen
  • EOrange

Which species produces the yellow color of the final solution?

  • A H C r O 2 2
  • B C r O 4 2
  • C C r O 2 5 2
  • D H C r O 4
  • E C r O 2 7 2

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

  • A K M n O 4
  • B H S O 2 4
  • C Z n
  • D N H 3
  • E H O 2 2

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

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 [ F e ( H O ) ] 2 6 2 +
  • B [ F e C l ] 4
  • C [ F e ( H O ) C l ] 2 4 2 +
  • D [ F e ( H O ) O H ] 2 5 2 +
  • E [ F e ( H O ) ( O H ) ] 2 4 2 +

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

  • AA lilac solution is produced.
  • BAn orange solid precipitates.
  • CA green solid precipitates.
  • DA lilac solid precipitates.
  • EA green solution is produced.

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

  • AAmmonia
  • BSodium thiocyanate
  • CSodium hydroxide
  • DSodium carbonate
  • ESodium sulfate

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 higher-frequency light is absorbed.
  • BThe geometry of the complex is unchanged and higher-frequency light is absorbed.
  • CThe complex changes from octahedral to tetrahedral and lower-frequency light is absorbed.
  • DThe geometry of the complex is unchanged and lower-frequency light is absorbed.
  • EThe complex changes from tetrahedral to octahedral and lower-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 O ( H O ) ] 2 2 4 +
  • B [ V ( H O ) ] 2 6 3 +
  • C [ V O ( H O ) ] 2 5 2 +
  • D [ V ( H O ) ] 2 6 2 +
  • E [ V O ( H O ) ] 2 2 4 2 +

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

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

  • AYellow
  • BPurple
  • CBlue
  • DGreen
  • EColorless

Q6:

Many cobalt(II) salts dissolve in water to produce the colored complex ion [ C o ( H O ) ] 2 6 2 + . 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 [ C o ( H O ) ] 2 6 2 + ion?

  • A Blue
  • B Green
  • C Red
  • D Yellow
  • E Pink

Draw an energy level diagram illustrating the arrangement of valence d electrons in the [ C o ( H O ) ] 2 6 2 + ion.

  • A
  • B
  • C
  • D
  • E

What is the formula of the major solid product when aqueous [ C o ( H O ) ] 2 6 2 + ions react with dilute ammonia?

  • A [ C o ( H O ) ( N H ) ] 2 3 3 3
  • B [ C o ( H O ) ( O H ) ] 2 4 2
  • C [ C o ( N H ) ( O H ) ] 3 3 3
  • D [ C o ( H O ) ( N H ) ] 2 4 3 2
  • E [ C o ( N H ) ( O H ) ] 3 4 2

When excess ammonia is added to aqueous [ C o ( H O ) ] 2 6 2 + 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?

  • A The complex converts from octahedral to tetrahedral and lower-frequency light is absorbed.
  • B The complex converts from tetrahedral to octahedral and lower-frequency light is absorbed.
  • C The geometry of the complex is unchanged and lower-frequency light is absorbed.
  • D The geometry of the complex is unchanged and higher-frequency light is absorbed.
  • E The complex converts from octahedral to tetrahedral and higher-frequency light is absorbed.

Q7:

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

  • A [ F e ( H O ) ] 2 6 3 +
  • B [ F e ( C N ) ] 6 3
  • C [ F e ( N H ) ] 3 6 3 +
  • D [ F e F ] 6 3
  • E [ F e C l ] 6 3

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