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प्रश्न
When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
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उत्तर
The compounds (A), (B), (C) and (D) are given as under:
A = \[\ce{MnO2}\]
B = \[\ce{K2MnO4}\]
C = \[\ce{KMnO4}\]
D = \[\ce{KlO3}\]
The reactions are explained as under:
\[\ce{\underset{(A)}{2MnO2} + 4KOH + O2 -> \underset{(B)}{2K2MnO4} + 2H2O}\]
\[\ce{3MnO^{2-}4 + 4H^+ -> \underset{(C)}{2MnO^{-}4} + MnO2 + 2H2O}\]
\[\ce{2MnO^{-}4 + H2O + Kl -> \underset{(A)}{2MnO2} + 2OH^{-} + \underset{(D)}{KlO3}}\]
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संबंधित प्रश्न
Account for the following:
Zn is not considered as a transition element.
Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?
How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.
For M2+/M and M3+/M2+ systems, the EΘ values for some metals are as follows:
| Cr2+/Cr | −0.9 V |
| Mn2+/Mn | −1.2 V |
| Fe2+/Fe | −0.4 V |
| Cr3/Cr2+ | −0.4 V |
| Mn3+/Mn2+ | +1.5 V |
| Fe3+/Fe2+ | +0.8 V |
Use this data to comment upon:
The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+.
What is meant by ‘disproportionation’?
What are inner transition elements?
Write the factors which are related to the colour of transition metal ions.
Give reasons Iron has the higher enthalpy of atomization than that of copper.
Explain why Mn2+ is more stable than Fe2+ towards oxidation to +3 state. (At. no. of Mn = 25, Fe = 26)
\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.
Why EΘ values for Mn, Ni and Zn are more negative than expected?
Transition elements show high melting points. Why?
When a brown compound of manganese (A) is treated with \[\ce{HCl}\] it gives a gas (B). The gas taken in excess, reacts with \[\ce{NH3}\] to give an explosive compound (C). Identify compounds A, B and C.
Mention any three processes where transition metals act as catalysts.
Read the passage given below and answer the following question.
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Are there nuclear reactions going on in our bodies? There are nuclear reactions constantly occurring in our bodies, but there are very few of them compared to the chemical reactions, and they do not affect our bodies much. All of the physical processes that take place to keep a human body running are chemical processes. Nuclear reactions can lead to chemical damage, which the body may notice and try to fix. The nuclear reaction occurring in our bodies is radioactive decay. This is the change of a less stable nucleus to a more stable nucleus. Every atom has either a stable nucleus or an unstable nucleus, depending on how big it is and on the ratio of protons to neutrons. The ratio of neutrons to protons in a stable nucleus is thus around 1 : 1 for small nuclei (Z < 20). Nuclei with too many neutrons, too few neutrons, or that are simply too big are unstable. They eventually transform to a stable form through radioactive decay. Wherever there are atoms with unstable nuclei (radioactive atoms), there are nuclear reactions occurring naturally. The interesting thing is that there are small amounts of radioactive atoms everywhere: in your chair, in the ground, in the food you eat, and yes, in your body. The most common natural radioactive isotopes in humans are carbon-14 and potassium-40. Chemically, these isotopes behave exactly like stable carbon and potassium. For this reason, the body uses carbon-14 and potassium-40 just like it does normal carbon and potassium; building them into the different parts of the cells, without knowing that they are radioactive. In time, carbon-14 atoms decay to stable nitrogen atoms and potassium-40 atoms decay to stable calcium atoms. Chemicals in the body that relied on having a carbon-14 atom or potassium-40 atom in a certain spot will suddenly have a nitrogen or calcium atom. Such a change damages the chemical. Normally, such changes are so rare, that the body can repair the damage or filter away the damaged chemicals. The natural occurrence of carbon-14 decay in the body is the core principle behind carbon dating. As long as a person is alive and still eating, every carbon-14 atom that decays into a nitrogen atom is replaced on average with a new carbon-14 atom. But once a person dies, he stops replacing the decaying carbon-14 atoms. Slowly the carbon-14 atoms decay to nitrogen without being replaced, so that there is less and less carbon-14 in a dead body. The rate at which carbon-14 decays is constant and follows first order kinetics. It has a half-life of nearly 6000 years, so by measuring the relative amount of carbon-14 in a bone, archeologists can calculate when the person died. All living organisms consume carbon, so carbon dating can be used to date any living organism, and any object made from a living organism. Bones, wood, leather, and even paper can be accurately dated, as long as they first existed within the last 60,000 years. This is all because of the fact that nuclear reactions naturally occur in living organisms. |
Which are the two most common radioactive decays happening in human body?
Sodium this sulphate is used in photography because of its:-
Account for the following:
Ce4+ is a strong oxidising agent.
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Explain the magnetic properties of d-block (or transition) elements.
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
