The proposition 'equal volumes of different gases contain equal numbers of molecules at the same temperature and pressure' is known as
- A.Avogadro's hypothesis
- B.Gay-Lussac's hypothesis
- C.Planck's hypothesis
- D.Kirchhoff's theory
Correct answer
Explanation
The correct answer is A, Avogadro's hypothesis. The Italian scientist Amedeo Avogadro proposed in 1811 that equal volumes of all gases, at the same temperature and pressure, hold the same number of molecules.
Avogadro's idea explained why gases combine in simple whole-number ratios by volume, and it separated the idea of an atom from that of a molecule. It leads to the result that one mole of any gas occupies about 22.4 litres at standard temperature and pressure. The number of particles in one mole, about 6.022 × 10²³, is called the Avogadro number in his honour. His hypothesis was widely accepted only after Stanislao Cannizzaro promoted it in 1860.
B is wrong because Gay-Lussac's law of combining volumes says gases react in simple volume ratios. C is wrong because Planck's hypothesis says energy is given out or absorbed in packets called quanta. D is wrong because Kirchhoff's laws deal with electric circuits and with the emission and absorption of radiation.
Exam tip: Avogadro (equal volumes, equal molecules), Boyle (P and V at constant T), Charles (V and T at constant P).
Practice Questions
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- A.1,2 and 3
- B.2 and 4
- C.1 and 3 only
- D.1 only
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- A.Joule
- B.Watt-hr
- C.Newton-metre
- D.kg-metre/sec²
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- A.Magnesium
- B.Zinc
- C.Aluminium
- D.Lead
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Read the full explanation →In an electric circuit, a wire of resistance 10 Ω is used. If this wire is stretched to a length double of its original value, the current in the circuit would become :
- A.half of its original value.
- B.double of its original value.
- C.one-fourth of its original value.
- D.four times of its original value.
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- A.Ernest Rutherford
- B.J.J. Thomson
- C.Niels Bohr
- D.Albert Einstein
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