1000 Questions Transition Metals

Question 1

Why are the elements with atomic numbers 21 to 30 classified together, as a series, in the periodic table?

Are there any sub-groups in this main group?

Question 2

_{Write down the electronic configurations of:}

scandium, scandium (III), manganese, manganese (II), chromium, iron (II), iron (III), copper, copper (I), zinc

Question 3

What is the oxidation number of chromium in:

CrO₄^2-, Cr³⁺, CrO₃, Cr₂O₃, CrF₂, [Cr(H₂O)₅NH₃]Cl₃, K₂SO₄.Cr₂(SO₄)₃.24H₂O

Question 4

An aqueous violet solution is treated with NaOH and a gelatinous blue green precipitate is forms. Excess hydroxide converts this to a clear green solution. When sodium Na₂O₂ is added a yellow solution forms which becomes orange when treated with excess acid. Explain.

Question 5

Complete and balance the following equations:

i) $MnO_4^-+H^++Fe^2^+\rightarrow$

ii) $Cr_2O_7^2^-+H^++NO_2^-\rightarrow$

iii) $MnO_2+MnO_4^-+OH^-\rightarrow$

iv) $MnO_2+H^++Br^-\rightarrow$

Question 6

Complex ions are readily formed when H₂O interacts with cations but not when H₃O⁺ interact with cations. Explain.

Question 7

The standard redox potential for a system are:

$V^3^+ + e^-\rightarrow V^2^+\: \: \: E^o=+0.20V$

$Fe^3^+ + e^-\rightarrow Fe^2^+\: \: \: E^o=-0.77V$

Predict what will happen when:

i) solution of 1M Fe³⁺ and 1M V³⁺are mixed;

ii) solution of 1M Fe²⁺ and 1M V³⁺are mixed;

iii) solution of 1M Fe³⁺ and 1M V²⁺are mixed;

Question 8

The colours of CrCl₃.6H₂O vary depending on concetration and temperature. Account for the possibility of this variation.

Question 9

How could one distinguish between [CrCl(H₂O)₅]Cl₂.H₂O] and [CrCl₂(H₂O)₄]Cl.2H₂O]?

Question 10

Starting with MnO₂ how could one prepare:

MnCl₂, MnO₄^2-, MnO₄^–

Question 11

Which is more acidic: Fe(NO₃)₂ or Fe(NO₃)₃? Explain.

Question 12

Transition metals can be used as catalysts. By showing examples, explain this statement.

Question 13

Transition metals have variable oxidation states. Explain.

Question 14

Transition metals form coloured compounds. Explain.

Question 15

When KSCN was added to an orange solution, a red blood solution was formed. Write the formula of the red blood complex formed.

Question 16

Fe₂(CO₃)₃ and FeI₃ cannot be prepared. Explain.

Question 17

The log K_stab values for two nickel complexes are:

8.74 for [Ni(NH₃)₆]²⁺ and 18.6 for [Ni(EDTA)]^2- 18.6

Both of these are octahedral complexes.
a) Write the equations for the formation of both of these complexes from hexaaquanickel(II) ions.
b) Explain why the stability of the two complexes is different.

Question 18

Explain how one would form CuI and CuCl. Considering that CuI and CuCl are insoluble compounds, explain why Cu₂SO₄ would be very difficult to produce.

Question 19

A 0.1M ZnSO₄ is much more acidic than a 0.1M MgSO₄. Explain.

Question 20

A sample A contains the elements Mn, N, C and O. Find the empirical formula from the following experimental data:

1.304g of the sample were dissolved in water and 25cm³ aliquots were used for analysis of Mn and N.

All the Mn in the sample was converted into MnO₄^– and it was titrated against 0.1036M FeSO₄. 36.42cm³ of FeSO₄ was needed to neutralise all of the MnO₄^–.

The N content was converted to ammonia and this was neutralised by 21.93cm³ of 0.0987M HCl.

The carbon contents was noted by burning 0.993g of sample A were 137.7cm³ of CO₂ measured at 25^oC and 1 atm.