Advertisements
Advertisements
Question
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
Advertisements
Solution
Potassium dichromate acts as a strong oxidizing agent. It is used as a primary standard in volumetric analysis. The oxidation action of dichromate ion in an acidic medium can be represented as follows:
\[\ce{Cr2O^2-_7 + 14H^+ + 6e^- -> 2Cr^3+ + 7H2O}\] (E– = 1.33 V)
H2S is oxidised to sulphur.
\[\ce{Cr2O^2-_7 + 8H^+ + 3H2S -> 2Cr^3+ + 7H2O + 3S}\]
APPEARS IN
RELATED QUESTIONS
Account for the following:
Cr2+ is a strong reducing agent.
How would you account for the following: Transition metals form complex compounds.
The `E_((M^(2+)//M))^Θ` value for copper is positive (+0.34 V). What is possibly the reason for this? (Hint: consider its high ΔaHΘ and low ΔhydHΘ)
To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.
What is meant by ‘disproportionation’?
Calculate the number of unpaired electrons in the following gaseous ions:
Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in an aqueous solution?
Write the formula of an oxo-anion of Chromium (Cr) in which it shows the oxidation state equal to its group number
Complete and balance the following chemical equations
`MnO_4^(-) + H_2O + I^(-) ->`
How is potassium dichromate prepared from chrome iron ore?
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?
(i) \[\ce{Cr}\]
(ii) \[\ce{Co}\]
(iii) \[\ce{Cu}\]
(iv) \[\ce{Ni}\]
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
Transition metals can act as catalysts because these can change their oxidation state. How does \[\ce{Fe(III)}\] catalyse the reaction between iodide and persulphate ions?
Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:
(activation energy, Threshold energy, increased, lowered, partially, full, d-d transition, Benzoic acid, benzaldehyde)
Only those transition metal ions will be coloured which have ______ filled d-orbitals facilitating ______.
The element with atomic number 46 belongs to
Catalytic hydrogenation of benzene gives
Photographic film and plates have - au essential ingredient of
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Account for the following:
Eu2+ with electronic configuration [Xe]4f76s2 is a strong reducing agent.
