Regents Chemistry redox, organic and nuclear chemistry: a complete skills guide to oxidation numbers, cells, hydrocarbons and radioactivity

Why these topics round out the course

Redox, organic chemistry and nuclear chemistry are the final core areas of the Regents course. Redox extends the electron-transfer ideas of bonding into reactions and cells; organic chemistry applies bonding and reaction types to carbon compounds; and nuclear chemistry deals with changes in the nucleus itself. All three rely heavily on the Reference Tables (Table J, Table N, Table P, Table Q, Table R, Table O and Table T). This guide ties together the matching dot-point pages, each with its own practice: oxidation numbers and redox reactions, half-reactions and balancing redox, electrochemical cells, organic chemistry and hydrocarbons, organic reactions and functional groups, and nuclear chemistry.

Oxidation numbers and redox

Assign oxidation numbers with the rules (free element $0$; monatomic ion equals its charge; H usually $+1$, O usually $-2$; sum to the overall charge). Oxidation is loss of electrons (number increases); reduction is gain (number decreases). The species oxidized is the reducing agent; the species reduced is the oxidizing agent. Half-reactions show the electrons explicitly (on the product side for oxidation, the reactant side for reduction), and the electrons lost must equal the electrons gained.

Electrochemical cells

A voltaic cell runs a spontaneous redox reaction to make electricity (chemical to electrical energy); an electrolytic cell uses electricity to force a non-spontaneous reaction (electrical to chemical energy). In both, oxidation is at the anode and reduction at the cathode, and electrons flow from anode to cathode through the wire. In a metal-metal voltaic cell, the more active metal (Table J) is the anode.

Organic chemistry

Carbon forms four bonds and chains, giving millions of compounds. The hydrocarbon series (Table Q) are alkanes ($\text{C}_n\text{H}_{2n+2}$), alkenes ($\text{C}_n\text{H}_{2n}$) and alkynes ($\text{C}_n\text{H}_{2n-2}$); name them with Table P prefixes and the series ending. Functional groups (Table R) define classes such as alcohols ($-\text{OH}$) and organic acids ($-\text{COOH}$). The main reactions are combustion, substitution, addition, esterification, saponification, fermentation and polymerization.

Nuclear chemistry

Nuclear reactions change the nucleus and can transmute elements. The radiations (Table O) are alpha ($^{4}_{2}\text{He}$), beta ($^{0}_{-1}e$), positron ($^{0}_{+1}e$) and gamma ($^{0}_{0}\gamma$). Balance a nuclear equation by conserving mass number and atomic number. Half-life is the time for half a sample to decay; after $n$ half-lives, the fraction left is $\left(\frac{1}{2}\right)^n$. Fission splits heavy nuclei; fusion joins light ones.

Check your knowledge

Attempt these under timed conditions, then check the solutions.

1. Determine the oxidation number of nitrogen in $\text{NH}_3$. (1 mark)
2. In $\text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}$, identify the reducing agent. (1 mark)
3. State where oxidation occurs in any electrochemical cell and the direction of electron flow. (2 marks)
4. Give the general formula and name the two-carbon member of the alkene series. (2 marks)
5. Name the organic reaction of an acid with an alcohol and its products. (2 marks)
6. A $40.0$ g sample has a half-life of $3.0$ days. Find the mass remaining after $9.0$ days. (2 marks)