Solution to Problem (4)

Solution:
a) In the reactants, the oxidation number of Al is zero (uncombined element) and the O.N. of Hg+ is +1 (the O.N. of an ion is equal to its charge)In the products, the O.N. of Al3+ is +3 (the O.N. of an ion is equal to its charge) while the O.N. of Hg is zero (uncombined element)the O.N. of Al increases from zero to +3, this is oxidation. The O.N. of Hg decreases from +1 to zero, this is reduction. Since this reaction involves a transfer of electrons between the reactants, then it is redox.
b) Al → Al3+ + 3e oxidation half reaction
(Hg+ + 1e → Hg) × 3 reduction half reaction
Overall redox reaction: Al + 3Hg+→ 3Hg+ Al3+
c) Since Al is the substance oxidized, then it has more tendency to lose electrons. Since Hg is the substance reduced, then it has less tendency to lose electrons.
d) Since the reaction between aluminum and mercury is a redox reaction, it involves a transfer of electrons, then an electric current is generated.
e) Chemical energy was converted into electric energy due to the reaction between mercury and aluminum, since they are two metals having different tendencies to lose electrons, saliva works as a solution that conducts electricity. This explains the word "battery".
f)
i) Saliva works as a conducting medium for the generated electric current, since it contains electrolytes (substances which are able to conduct electricity
ii) Amalgam fillings are used in dentistry since they are extremely durable and able to withstand the grinding and chewing of your back teeth over long periods of time.
iii) Mercury is extremely toxic to the nervous system, kidneys, and livers. Mercury may result in defects in fetuses for pregnant women
g) Of course not, since amalgam fillings contain mercury which is a highly toxic metal to human body, being able to damage vital organs in human body.