Which one of the following is not explained by the Dalton's atomic theory ?
- A.Law of conservation of mass
- B.Law of constant composition
- C.Presence of different kind of sub-atomic particles in an atom
- D.Law of multiple proportion
Correct answer
Explanation
The correct answer is C, Presence of different kind of sub-atomic particles in an atom. Dalton held that the atom is the smallest, indivisible particle of matter, so his theory cannot explain particles inside the atom.
John Dalton put forward his atomic theory in 1808. It said that matter is made of tiny indivisible atoms, that atoms of one element are identical in mass and properties, that atoms combine in simple whole number ratios to form compounds, and that atoms are neither created nor destroyed in a chemical reaction. The electron (J.J. Thomson, 1897), the proton and the neutron (Chadwick, 1932) were discovered much later and proved the atom divisible.
A is wrong because atoms being neither created nor destroyed explains conservation of mass. B is wrong because fixed ratios of atoms explain constant composition. D is wrong because simple whole number ratios explain multiple proportions.
Exam tip: Dalton explained the laws of chemical combination but failed on sub-atomic particles and isotopes.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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