Question 51. Calcium carbide is also used for ripening fruit artificially in some countries. Calcium carbide reacts with water to produce acetylene, which acts as an artificial ripening agent. Industrial-grade calcium carbide may contain traces of arsenic and phosphorus which makes it a human health concern Consider the following statements about acetylene
(a) It is used in welding industry
(b) It is a raw material for preparing plastics
(c) It is easily obtained by mixing silicon carbide and water
of these statements

Question 52. Coal is sedimentary rock.  A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, then bituminous coal, and lastly anthracite. The variety of coal which the deposit contains recognizable traces of the original plant material is

Question 53. Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal feces, and kitchen waste can be converted into a gaseous fuel called biogas. Gobar gas contains mainly

Question 54. Match List I and List II and select the correct answer by using the codes given below.
List I                                                List II
A. Vodka                                           1. Apples
B. Brandy                                          2. Potatoes
C. Cidar                                             3. Barley
D. Whisky                                         4. Grapes

Question 55. Water softening is the reduction of the concentration of metal cations in hard water. Water softening is the process in which
(a) impurities are removed from water
(b) dissolved calcium ions are removed from hard water
(c) dissolved magnesium ions are removed from hard water
(d) water is boiled for extracting all salts from it

Question 56. At room temperature, it is a colorless, non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic effects. It is known as "laughing gas" due to the euphoric effects of inhaling it. Which one of the following is the gas we are talking about?

Question 57. The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. It is carefully regulated by a number of homeostatic mechanisms, which exert their influence principally through the respiratory system and the urinary system in order to control the acid-base balance and respiration. What is the normal pH level of blood of a normal person?

Question 58. Arrange the following metals in the decreasing order of their relative abundance in earth's crust after aluminium
(a) Calcium
(b) Iron
(c) Sodium
(d) Magnesium

Question 59. Match List I and List II and select the correct
List I                                           List II
A. Diamond                        1. Fertiliser
B. Ammonium Sulphate  2. Oxidising agent
C. Sodium Periodate        3. Dry cells
D. Manganese dioxide    4. Abrasive

Question 60. When one of the following statements is correct?