Which of the following are oxidation reactions? I. Rusting of iron II. Burning of fuel III. Rancidity of oils and fats IV. Browning of fruits Select the correct answer using the code given below.
- A.I, II and III only
- B.I, II and IV only
- C.III and IV only
- D.I, II, III and IV
Correct answer
Explanation
The correct answer is D, I, II, III and IV. In each of the four changes a substance combines with oxygen from the air, which is oxidation.
Rusting is the slow oxidation of iron in the presence of moisture, giving hydrated iron(III) oxide, Fe2O3·xH2O. Burning of fuel is rapid oxidation, or combustion, in which carbon and hydrogen combine with oxygen to give carbon dioxide, water and heat. Rancidity is the oxidation of fats and oils, which gives a bad smell and taste; it is slowed by antioxidants, airtight packing and flushing chip packets with nitrogen. Browning of a cut apple or potato happens when the enzyme polyphenol oxidase oxidises phenolic compounds on exposure to air.
A is wrong because it leaves out browning of fruits.
B is wrong because it leaves out rancidity.
C is wrong because it leaves out rusting and burning, the clearest oxidation reactions.
Exam tip: rusting, combustion, rancidity and browning of fruit are all oxidation; nitrogen in chip packets prevents rancidity.
Practice Questions
View allThe mass number of an element is NOT changed when it emits
- A.Alpha and Beta radiations only
- B.Alpha and Gamma radiations only
- C.Beta and Gamma radiations only
- D.Alpha, Beta and Gamma radiations
Show answer
Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.
Read the full explanation →Which one among the following statements about facilitated transport in plants is correct?
- A.All passive transports are types of facilitated transport.
- B.Facilitated transport is an example of active transport.
- C.Water moves across plasma membrane by active transport.
- D.Facilitated transport requires assistance of carrier proteins.
Show answer
In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.
Read the full explanation →Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?
- A.Richard Feynman
- B.Murray Gell-Mann
- C.Albert Einstein
- D.Niels Bohr
Show answer
The American physicist Murray Gell-Mann proposed quarks in 1964 and gave them their name. Gell-Mann, and independently George Zweig, suggested that protons, neutrons and other such particles are built from smaller units.
Read the full explanation →The spindle fibre is attached to which of the following specific regions of the chromosomes?
- A.Kinetochore
- B.Chromonema
- C.Telomere
- D.Centriole
Show answer
Spindle fibres attach to the kinetochore, a disc-shaped protein structure on the centromere of each chromosome. During cell division the spindle, made of microtubules, pulls the copies of each chromosome apart.
Read the full explanation →Which one of the following is the chemical name of heavy water?
- A.Hydrogen oxide
- B.Deuterium dioxide
- C.Deuterium oxide
- D.Heavy hydrogen oxide
Show answer
Heavy water is D₂O: two atoms of deuterium joined to one atom of oxygen. Deuterium is the isotope of hydrogen with one proton and one neutron in its nucleus, so it is about twice as heavy as ordinary hydrogen.
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