Chemistry (Part-IX)

41. Which of the following has a tetragonal crystal system? [S.S.C. Online C.H.S.L. (T-I) 10.08.2021 (Shift-I) ]

(a) Potassium nitrate
(b) Calcium sulphate
(c) Zinc oxide
(d) Cadmium sulphide

Correct Answer: (b) Calcium sulphate

Solution:Calcium sulfate (CaSO₂) has a tetragonal crystal system in its structure. In this, the tetrahedral form of the sulfate ion is associated with the calcium ion (Ca²⁺) as-

42. _______ is an active ingredient in all alcoholic drinks. [S.S.C. JE Electrical Exam 10.12.2020 (Shift-II) ]

(a) Pentane
(b) Ethanol
(c) Butane
(d) Propane

Correct Answer: (b) Ethanol

Solution:Ethanol is an active ingredient in all alcoholic beverages. It is used in the manufacture of varnishes, polishes, chloroform, cosmetics, etc. It is also used in motor vehicles by mixed with petrol.

43. _______ is the main fatty acid in coconut oil and in palm kernel oil that has antimicrobial properties. [S.S.C. JE Mechanical Exam 27.10.2020 (Shift-II) ]

(a) Acetic acid
(b) Sulphuric acid
(c) Lactic acid
(d) Lauric acid

Correct Answer: (d) Lauric acid

Solution:Lauric acid is found in coconut oil and palm kernel oil. Lauric acid is used in the soap and cosmetic manufacturing industries. It is also used in the treatment of viral infections including influenza (flu).

44. Which of the following acids is used as an anti-septic? [S.S.C. JE Mechanical Exam 27.10.2020 (Shift-II) ]

(a) Phosphoric acid
(b) Boric acid
(c) Citric acid
(d) Sulphuric acid

Correct Answer: (b) Boric acid

Solution:Boric acid [H₃BO₃ or B(OH)₃] is used as an antiseptic. It is a weakly acidic hydrate of boric oxide with mild antiseptic, antifungal, and antiviral properties.

45. Which one of the following forms of phosphorus is most reactive? [S.S.C. Online Graduate Level (T-I) 31.08.2016 (Shift-III) ]

(a) Black phosphorus
(b) White phosphorus
(c) Violet phosphorus
(d) Red phosphorus

Correct Answer: (b) White phosphorus

Solution:White phosphorus, represented by the chemical formula P₄, is the most reactive substance. It starts burning automatically in the air because its ignition temperature is around 30°C. White phosphorus is kept in water to protect it from the air. The reason for its rapid reactivity is the unstable or strained tetrahedral structure.

46. The Chemical formula of Methanol is ________ . [S.S.C. Online CHSL (T-I) 22.01.2017 (Shift-II) ]

(a) C₂H₅OH
(b) CH₃(OH)₂
(c) CH₃OH
(d) CH₄OH

Correct Answer: (c) CH₃OH

Solution:Methanol is also known as methyl alcohol. It is an organic compound with the chemical formula CH₃OH. Pure methanol is an important substance used in chemical synthesis. It is a toxic liquid and is not potable.

47. Which of the following is not a natural source of hydrocarbons? [C.P.Q. S.I. 6.06.2016 (Shift-I) ]

(a) Natural Gas
(b) Coal
(c) Petroleum
(d) Mica

Correct Answer: (d) Mica

Solution:Natural gas, coal, and petroleum are all natural sources of hydrocarbons. Mica is a' versatile mineral, which is found in the form of fragments in igneous and metamorphic rocks. It is a complex silicate compound. Asbestos is often found in igneous rocks.

48. Chemical composition of cement is- [S.S.C. Online Graduate Level (T-I) 4.09.2016 (Shift-II) ]

(a) Limestone and Clay
(b) Limestone, Clay and Gypsum
(c) Limestone and Gypsum
(d) Clay and Gypsum

Correct Answer: (b) Limestone, Clay and Gypsum

Solution:Cement contains limestone [CaO], gypsum [CaSO₄.2H₂O] and clay, some other substances like alumina (Al₂O₃) iron oxide (Fe₂O₃) and silicon dioxide (SiO₂) etc. are also added.

49. ______ decreases the rate of setting of cement. [S.S.C. Online CHSL (T-I) 24.01.2017 (Shift-III) ]

(a) Alumina
(b) Silica
(c) Gypsum
(d) Magnesium Oxide

Correct Answer: (c) Gypsum

Solution:Gypsum reduces the rate of solidification of cement. From the point of view of chemical structure, it is the sulphate of calcium, in which two molecules of water are also present. The chemical formula of gypsum is (CaSO₄ 2H₂O ) It is a layered mineral, also known as 'lanite'. Gypsum is used in making plaster of Paris, fertilizer, glass, porcelain, fire-resistant brick, etc.

50. Chemical formula of gypsum is _______ . [S.S.C. Online CGL (T-I) 03.12.2022 (Shift-III) ]

(a) CaSO₄.2H₂O
(b) CaSO₄.H₂O
(c) CaSO₄
(d) CaSO₄ .(1/2)H₂O

Correct Answer: (a) CaSO₄.2H₂O

Solution:Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO₄.2H₂O.

Calcium Chlorohypochlorite(Bleaching Powder) Ca(ClO)₂
Sodium bicarbonate (Baking soda) - NaHCO₃
Calcium Sulphate Hemihydrate(Plaster of Paris) - (CaSO₄ . 1/2 2H₂O)