The paste of a white material in water is used to maintain a fractured bone fixed in place. The white material used is called
- A.bleaching powder
- B.plaster of Paris
- C.powder of zinc oxide
- D.lime powder
Correct answer
Explanation
The correct answer is B, plaster of Paris. Plaster of Paris mixed with water sets within minutes into a hard mass, which is why doctors use it to make casts that hold broken bones in place.
Plaster of Paris is calcium sulphate hemihydrate, CaSO4·½H2O. It is made by heating gypsum, CaSO4·2H2O, to about 373 K, when it loses part of its water. When water is added again, it turns back into gypsum and sets as a hard solid. Besides plaster casts, it is used for making toys, decorative materials, statues and moulds, and for smoothing walls. It must be stored in a moisture-proof container, or it slowly sets.
Option A is wrong because bleaching powder, calcium oxychloride, is used to disinfect water and bleach cloth. Option C is wrong because zinc oxide powder is used in ointments, sunscreens and as a white pigment, not for setting bones. Option D is wrong because lime powder, calcium oxide or hydroxide, is used for whitewashing and in mortar.
Exam tip: Gypsum heated becomes plaster of Paris; plaster of Paris with water becomes gypsum again.
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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