Consider the following statements: While diluting concentrated nitric acid solution 1. the concentration of [H3O+] ions/volume increases 2. water must be added slowly to concentrated acid 3. acid must be added slowly to water Which of the statements given above is/are correct?
- A.1, 2 and 3
- B.1 and 2 only
- C.3 only
- D.2 and 3 only
Correct answer
Explanation
The correct answer is C, 3 only. Only statement 3 is correct: the acid must be added slowly to water, and dilution lowers the concentration of hydronium ions per unit volume.
Mixing a concentrated acid such as nitric or sulphuric acid with water is a highly exothermic process. If water is poured into the acid, the small amount of water can boil at once and splash the hot, corrosive acid out of the container, and the glass may crack from the heat. Adding the acid slowly to a large volume of water, with constant stirring, lets the heat spread out safely. Dilution spreads the same number of H3O+ ions through a larger volume, so their concentration falls and the pH rises.
A is wrong because statements 1 and 2 are false. B is wrong because it picks the two false statements. D is wrong because statement 2, adding water to acid, is the unsafe method.
Exam tip: Always add acid to water, never water to acid; dilution lowers [H3O+].
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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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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