What is the ratio by mass of nitrogen and hydrogen in ammonia?
- A.11 : 1
- B.14 : 3
- C.11 : 3
- D.14 : 1
Correct answer
Explanation
The correct answer is B, 14 : 3. Ammonia is NH3, so one nitrogen atom of mass 14 is joined to three hydrogen atoms of mass 1 each, giving 14 : 3 by mass. This is the law of constant proportions given by Proust in 1799: a pure compound always contains the same elements in the same ratio by mass, whatever its source. The NCERT Class 9 chapter uses exactly these examples, water H2O with hydrogen to oxygen 1 : 8 and ammonia NH3 with nitrogen to hydrogen 14 : 3. Remember that the ratio by mass is not the ratio by atoms; by atoms ammonia is 1 : 3, by mass it is 14 : 3 because nitrogen is fourteen times heavier than hydrogen. A is wrong because 11 is not the atomic mass of nitrogen. C is wrong for the same reason, even though the hydrogen part is right. D is wrong because it counts only one hydrogen atom instead of three. Exam tip: water 1 : 8, ammonia 14 : 3, carbon dioxide 3 : 8, all by mass.
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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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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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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