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An inert electrode like Platinum (Pt) is used in a half-cell. What is its primary function?
The text explains: 'Sometimes metals like platinum or gold are used as inert electrodes. They do not participate in the reaction but provide their surface for oxidation or reduction reactions and for the conduction of electrons.'
Why is the standard electrode potential (E$^{\text{o}}$) of Sc$^{3+}$/Sc not listed in Table 4.2?
The text states, 'The low value for Sc (referring to E$^{\text{o}}$ (M$^{3+}$/M$^{2+}$) for elements that can form M$^{2+}$) reflects the stability of Sc$^{3+}$ which has a noble gas configuration.' Sc$^{3+}$ is extremely stable and difficult to reduce to a lower oxidation state (or metal), making the standard potential for Sc$^{3+}$/Sc irrelevant in the context of standard M$^{2+}$/M potentials or implying that Sc$^{2+}$ is not readily formed or reduced.
If the E$^{\text{o}}$ for a reduction reaction is positive, what does it indicate about the species being reduced?
A positive E$^{\text{o}}$ for a reduction half-reaction (e.g., Ag$^{+}$ + e$^{-}$ $\to$ Ag, E$^{\text{o}}$ = +0.80V) indicates that the species being reduced (Ag$^{+}$ in this case) has a strong tendency to gain electrons and get reduced. A species that readily accepts electrons and gets reduced is a strong oxidizing agent.
Which of the following statements about the state of elements known in 1800 and 1865 is correct?
According to the NCERT text, 'In 1800, only 31 elements were known. By 1865, the number of identified elements had more than doubled to 63.' This directly supports option o1.
Who was the first scientist to consider the idea of trends among properties of elements, noting a similarity among groups of three elements (triads)?
The NCERT text states, 'The German chemist, Johann Dobereiner in early 1800’s was the first to consider the idea of trends among properties of elements. By 1829 he noted a similarity among the physical and chemical properties of several groups of three elements (triads).'
In Dobereiner's Triads, what was the approximate relationship between the atomic weight of the middle element and the other two elements in the triad?
The NCERT text explains Dobereiner's observation: 'In each case, he noticed that the middle element of each of the triads had an atomic weight about half way between the atomic weights of the other two (Table 3.1).'
John Alexander Newlands profounded the Law of Octaves in 1865. What was the basis of his arrangement of elements?
According to the NCERT text, 'The English chemist, John Alexander Newlands in 1865 profounded the law of octaves. He arranged the elements in increasing order of their atomic weights and noted that every eighth element had properties similar to the first element.'
For which elements did Newlands's Law of Octaves seem to be true?
The NCERT text specifies, 'Newlands’s Law of Octaves seemed to be true only for elements up to Calcium.'
Which two chemists are credited with the development of the Periodic Law, as we know it today, proposing that similarities appear in physical and chemical properties at regular intervals when elements are arranged by atomic weight?
The NCERT text states, 'The Periodic Law, as we know it today owes its development to the Russian chemist, Dmitri Mendeleev (1834-1907) and the German chemist, Lothar Meyer (1830-1895). Working independently, both the chemists in 1869 proposed that on arranging elements in the increasing order of their atomic weights, similarities appear in physical and chemical properties at regular intervals.'
Lothar Meyer's contribution to the periodic classification involved plotting physical properties like atomic volume, melting point, and boiling point against which atomic characteristic?
The text mentions, 'Lothar Meyer plotted the physical properties such as atomic volume, melting point and boiling point against atomic weight and obtained a periodically repeated pattern.'
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