The galvanic cell corresponding to the given redox reaction can be represented as:
\(Zn[Zn^{2+}_{(aq)}∥Ag^+_{(aq)}]Ag\)
(i) \(Zn\) electrode is negatively charged because at this electrode, \(Zn\) oxidizes to \(Zn ^{2+}\) and the leaving electrons accumulate on this electrode.
(ii) Ions are the carriers of current in the cell.
(iii) The reaction taking place at \(Zn\) electrode can be represented as:
\(Zn_{(s})\rightarrow Zn^{2+}_{(aq)}+2e^−\)
And the reaction taking place at Ag electrode can be represented as:
\(Ag^+_{(aq)}+e^-\rightarrow Ag_{(s)}\)
Answer the following :
(a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained? The rocket or the atmosphere?
(b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. Yet the work done by the gravitational force over every complete orbit of the comet is zero. Why ?
(c) An artificial satellite orbiting the earth in very thin atmosphere loses its energy gradually due to dissipation against atmospheric resistance, however small. Why then does its speed increase progressively as it comes closer and closer to the earth ?
(d) In Fig. 5.13(i) the man walks 2 m carrying a mass of 15 kg on his hands. In Fig. 5.13(ii), he walks the same distance pulling the rope behind him. The rope goes over a pulley, and a mass of 15 kg hangs at its other end. In which case is the work done greater ?
Redox reactions are chemical reactions where oxidation and reduction take place simultaneously. In this type of reaction, there is a gain of electrons for one chemical species while the other loses electrons or simply involves transfer of electrons. The species that loses electrons is oxidized while the one that gains electrons is reduced.
Redox reactions can be differentiated into 4 categories namely combination reactions, decomposition reactions, displacement reactions, and disproportionation reactions. Each is explained separately below:
In this, the molecules combine to form new compounds. For example, when magnesium reacts to nitrogen.
Opposite to the combination reaction, here there is a breakdown of compounds to simpler substances. For example, electrolysis of water.
In this, the more reactive metal will displace the less reactive one in a chemical reaction. The reactivity of an element is represented in a series called the reactivity series (arranged in decreasing order of reactivity) which makes it easier to determine the chemical reaction and its products.
This is a peculiar type of reaction where an element showing a particular oxidation state will be oxidized and reduced simultaneously. Another thing to note is that these reactions will always have an element that can exhibit three oxidation states.