Which chemical is used for whitening (or removal of colours) of cloth in cloth industries?
- A.Sodium carbonate
- B.Sodium hydrogencarbonate
- C.Calcium oxychloride
- D.Calcium chloride
Correct answer
Explanation
The correct answer is C, Calcium oxychloride. Calcium oxychloride (CaOCl2) is bleaching powder, and the chlorine it releases removes colour from cotton and linen in the textile industry. It is made by passing chlorine gas over dry slaked lime, Ca(OH)2. When it reacts with water or a dilute acid it gives out chlorine, and this chlorine oxidises the colouring matter into colourless substances. Bleaching powder is also used to bleach wood pulp in paper mills and to disinfect drinking water, which is why it smells of chlorine. A is wrong because sodium carbonate is washing soda, used to remove the permanent hardness of water and in making glass. B is wrong because sodium hydrogencarbonate is baking soda, used in cooking and as an antacid. D is wrong because calcium chloride is a drying agent that absorbs moisture, not a bleach. Exam tip: bleaching powder CaOCl2, washing soda Na2CO3·10H2O, baking soda NaHCO3.
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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