SOLVED PAPER 2021 (CDS) (II) (General Studies)

Total Questions: 120

81. Refraction of light, as it enters from one transparent medium to another, is due to

Correct Answer: (c) change in speed of light
Solution:

Light refracts whenever it travels at an angle into a substance with a different refractive index (optical density). This change of direction is caused by a change in speed. When light travels from air into water, it slows down, causing it to change direction slightly. This change of direction is called refraction.

82. A bus starting from a bus-stand and moving with uniform acceleration attains a speed of 20 km/h in 10 minutes. What is its acceleration ?

Correct Answer: (b) 120 km/h²
Solution:

83. Which one of the following is the correct reactivity order of metals reacting with dilute HCl ?

Correct Answer: (a) Mg > AI > Zn > Fe
Solution:

Those metals which are above in the reactivity series displace hydrogen from dilute acids as nitrogen monoxide, dinitrogen monoxide. The arrangement of metals in decreasing order of their reactivities is called reactivity series or activity series of metals. This is a decreasing order of chemical reactivity. Thus, correct sequence is Mg > Al > Zn > Fe.

84. Which one of the following acids is secreted by leaves of Nettle that causes painful stings ?

Correct Answer: (a) Methanoic acid
Solution:

Leaves of the nettle plant secrete methanoic acid which causes a painful sting on touching. Nettle stings contain formic acid, histamine and other chemicals. Formic acid is also known as methanoic acid (HCOOH).

85. Which of the following statements is/are correct ?

1. All the bases are alkali.
2. All alkalis dissolve in water.
3. Alkalis are soapy-to-touch, bitter in taste and corrosive in nature.

Select the correct using the codes given below.

Correct Answer: (c) 2 and 3
Solution:

Statement 2 and 3 are correct. Alkali is a base. It is a base that dissolves in water which is very important to remember. Not all bases are alkali but all alkali is base. Bases that dissolve in water are alkali. Alkalis are soapy to touch as they react with oils of our skin to form soaps. that have an alkaline pH, such as baking soda, often have a bitter flavor. Alkalis are very corrosive in nature and penetrate deeply.

86. Which one of the following materials is present in a guard tube (drying tube) that is used for preparation of HCl gas?

Correct Answer: (a) Calcium chloride
Solution:

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing anhydrous calcium chloride. The role of anhydrous calcium chloride taken in the guard tube is to absorb moisture from the gas, moisten the gas and absorb moisture the gas.

87. Fertilizers are used to obtain higher yields of crops. However, all nutrients are usually not available in fertilizers. Which one of the following nutrients is usually not available in fertilizers?

Correct Answer: (a) Iron
Solution:

Most fertilizers that are commonly used in agriculture contain the three basic plant nutrients: nitrogen, phosphorus and potassium. Iron is a micronutrient for plant growth which is not available in fertilizers. Iron helps the plant move oxygen throughout the roots, leaves and other parts of the plant, producing the green colour that lets you know your plant is healthy. Many plants also rely on iron to complete the enzyme functions that keep the plant thriving.

88. Rupa and Sachin observed an animal in their school garden. Rupa called it an insect while Sachin identified it as an earthworm. Which one of the following characteristics confirms that it is an insect?

Correct Answer: (a) The animal had jointed legs.
Solution:

Insects have segmented bodies, which are divided into head, thotax and abdomen, three pairs of jointed legs and external skeletons (exoskeletons) made up of chitin. The word ‘arthropod’ refers to all invertebrates with jointed legs. Arthropods also have a hard exoskeleton, like you might see on a crab or on a beetle.

89. Animals which are marine, bilaterally symmetrical, have a coelom and a notochord, but never form a vertebral column are placed under which one of the following groups?

Correct Answer: (a) Chordata
Solution:

Animals in the phylum Chordata share five key chacteristics that appear at some stage during their development: a notochord, a dorsal hollow (tubular) nerve cord, pharyngeal gill arches or slits, a post-anal tail and an endostyle/thyroid gland.

90. What is the location of intercalary meristem in plants?

Correct Answer: (a) Base of the leaves or internodes
Solution:

Intercalary Meristems are located at the internodes or the base of the leaves. The intercalary meristems help in increasing the length of the internode of stem. This is usually seen in monocotyledonous plants.