451. Which one of the following chemicals had been in use till now for making artificial clouds?
1. Potassium Nitrate
2. Heavy Water
3. Sulphur Iodide
4. Silver Iodide
Option “4” is correct. Cloud seeding is the process of spreading either dry ice or more commonly silver Iodide into the upper part of clouds to try to stimulate the precipitation process and form rain.
452. Which of the following main elements is used in making matchbox?
1. Graphite
2. Phosphorous
3. Silicon
4. Sodium
Option “2” is correct. The safety matchbox ignites due to the extreme reactivity of phosphorus with the potassium chlorate on the match head. Phosphorus is a highly reactive, non-toxic-chemical used for making the head of a matchstick.
453. ‘Humus’ is an example of-
1. Soil structure
2. Crystalloids
3. Organic colloids
4. None of the above
Option “3” is correct. Humus usually refers to the natural decay of material such as leaves in the soil’s top layer. It is a dark organic material that forms in the soil when plant and animal matter decays.
Option “4” is correct. Solid directly changes into vapour and this process is called sublimation. The sublimation is the process in which some substances upon heating directly changes into vapour.
456. Which one of the following is liquid at ordinary temperature?
1. Lead
2. Nickel
3. Mercury
4. Tin
Option “3” is correct. Mercury is the only metal which is liquid at ordinary temperature.
457.Match List-I with List-II and select the correct answer using the codes given below the lists: 1. A
2. B
3. C
4. D
Option “4” is correct. Diamond is an allotrope of Carbon . Marble is a metamorphic rock composed mainly of crystalline calcium Carbonate or Calcium Magnesium Carbonate. The most common component of sand is Silicon dioxide in the form of quartz. Ruby is considered as one of the four precious stones together with Sapphire, Emerald and Diamond. In Chemistry, the ruby gemstone is a mixture of Aluminium, Oxygen and Chromium.
458. Which among the following is an endothermic reaction?
1. Respiration
2. Combustion
3. Sweating
4. Burning of natural gas
Option “3” is correct. Endothermic process describes a process or reaction in which the system absorbs energy from its surroundings. Sweating is a endothermic reaction.
459. Name the catalyst used in the conversion of milk into curd?
1. Pepsin
2. Invertase
3. Lactase
4. Diastase
Option “3” is correct. Milk is converted into curd or yogurt by the process of fermentation. Milk consists of globular proteins called casein. The curd forms because of the chemical reaction between the lactic acid bacteria and casein. Thus, lactase is the catalyst used in conversion of milk into curd.
460. _________ gets converted to phosgene, when exposed to sunlight.
1. Chloroform
2. Acetone
3. Benzene
4. Propylene
Option “1” is correct. Phosgene can form from chloroform, in presence of oxygen and UV light.
1. A