Which one of the following nitrogen oxides has the highest oxidation state of nitrogen?
- A.NO
- B.NO2
- C.N2O
- D.N2O5
Correct answer
Explanation
The correct answer is D, N2O5. In dinitrogen pentoxide, nitrogen has an oxidation state of +5, the highest it can reach, because a nitrogen atom has five electrons in its outer shell. To work it out, give each oxygen atom an oxidation state of -2 and make the total of the neutral molecule zero. In N2O5 the five oxygens give -10, so the two nitrogens share +10, which is +5 each. N2O5 is a white solid and the acid anhydride of nitric acid (HNO3), in which nitrogen is also +5; it reacts with water to form nitric acid. Option A is wrong because in NO (nitric oxide) one oxygen at -2 makes nitrogen +2. Option B is wrong because in NO2 (nitrogen dioxide, the brown gas of smog) two oxygens at -4 make nitrogen +4. Option C is wrong because in N2O (nitrous oxide, laughing gas) one oxygen at -2 is shared by two nitrogens, giving +1 each. Exam tip: the oxides of nitrogen run N2O (+1), NO (+2), N2O3 (+3), NO2 (+4), N2O5 (+5).
Practice Questions
View allThe rate of evaporation of liquid does not depend upon
- A.temperature
- B.its surface area exposed to the atmosphere
- C.its mass
- D.humidity
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Evaporation is a surface process, so its rate depends on conditions at the surface of the liquid, not on how much liquid there is in total.
Read the full explanation →Which one of the following is considered as a compound ?
- A.Silicon
- B.Tin
- C.Sugar solution
- D.Calcium carbonate
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Calcium carbonate, CaCO3, is a compound because calcium, carbon and oxygen are chemically combined in it in a fixed ratio.
Read the full explanation →'Altitude sickness' is caused at high altitude due to
- A.high partial pressure of oxygen
- B.low partial pressure of oxygen
- C.low level of haemoglobin
- D.high partial pressure of carbon dioxide
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As one climbs, air pressure falls, so each breath delivers oxygen at a lower partial pressure and less of it passes from the lungs into the blood.
Read the full explanation →Which one of the following is not a characteristic of a compound?
- A.Composition is variable.
- B.All particles of compound are of only one type.
- C.Particles of compound have two or more elements.
- D.Its constituents cannot be separated by simple physical methods.
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A compound always has a fixed composition by mass, so a variable composition is a property of mixtures, not compounds.
Read the full explanation →A positively charged particle (alpha-particle) is projected towards west in a horizontal plane. It is deflected towards north in the same plane by a magnetic field. Which one among the following is the direction of the magnetic field?
- A.Towards south
- B.Towards east
- C.Vertically downwards
- D.Vertically upwards
Show answer
The magnetic force on a moving charge is F = q(v × B), and only an upward field turns a westward-moving positive charge towards the north.
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