Previous Year Questions General Science for CDS & CAPF: 12th October


Previous year questions must be prepared when it comes to the preparation of CDS & CAPF examinations. Defenceadda is providing you with the previous year questions of General Science Section.


Q1. The law enforcement agencies use a chemical test to approximate a person’s blood alcohol level. The person underpinning the test blows into the mouthpiece of a bag containing sodium dichromate solution in acidic medium. A chemical reaction with ethanol changes the colour of the solution from 
(a) Orange to green 
(b) Orange to colorless 
(c) Yellow to orange 
(d) Colorless to orange 

Q2. Scuba divers are at risk due to high concentration of dissolved gases while breathing air at high pressure under water. The tanks used by Scuba divers are filled with
(a) Air diluted with helium
(b) O_2
(c) N_2
(d) a mixture of N_2 and helium 

Q3. Which one of the following is not needed in a nuclear fission reactor?  
(a) Moderator 
(b) Coolant 
(c) Accelerator 
(d) Control device 

Q4. When items or jewellery made of metals such as copper or nickel are placed in a solution having a salt of gold, at thin film of gold is deposited by  
(a) Cooling to below 0°C
(b) Heating above 100°C 
(c) Passing an electric current 
(d) Just keeping it for 10 min 

Q5. Heavy water implies 
(a) Water which is used in heavy industries such as thermal power plants 
(b) water which has maximum density 
(c) Deuterated water 
(d) None Of These

Q6. Which one among the following is a sin smelling agent added to LPG cylinder to help the detection of gas leakage? 
(a) Ethanol 
(b) Thioethanol 
(c) Methane 
(d) Chloroform 

Q7. A body is charged negatively. It implies that  
(a) it has lost some of its protons 
(b) it has acquired some electrons from outside 
(c) it has lost some of its electrons 
(d) None of the above 

Q8. Which one among the following metals is used for making boats because it does not corrode by sea water?  
(a) Tungsten 
(b) Nickel 
(c) Antimony 
(d) Titanium 

Q9. Contact lenses are made from  
(a) polyvinyl chloride 
(b) polystyrene 
(c) lucite 
(d) Teflon 

Q10. Water is a good coolant and is used to cool the engines of cars, buses, trucks etc. It is because water has a  
(a) high specific heat 
(b) low surface tension 
(c) high boiling point 
(d) Teflon 

SOLUTIONS
S1. Ans.(a)
Sol. On reaction with ethanol the colour of the solution changes from, orange to green. 

S2. Ans.(a)
Sol. The tanks used by Scuba divers are filled with air diluted with helium (i.e., He-O_2 mixture) because unlike nitrogen, helium is not soluble in blood even under high pressure. 

S3. Ans.(c)
Sol. Substances like graphite and heavy water are used as moderator to slow down the speed of neutrons. Cd or B are used as control rods to control rate of fission by absorbing neutrons. 
Coolant like heavy water or molten sodium is used to carry away the heat. 

S4. Ans.(c)
Sol. The process of depositing a thin layer of one metal over the surface of other metal by the process of electrolysis is known as electroplating. Hence, when items or jewellery made of metals such as copper or nickel are placed in a solution having a salt of gold, a thin film of gold is deposited by passing an electric current. 

S5. Ans.(c)
Sol. Heavy water or deuterium oxide (D_2 O) is an oxide of deuterium which is an isotope of hydrogen. 

S6. Ans.(b)
Sol. Ethyl mercaptan or thioethanol (C_2 H_5 SH) is added during filling of LPG cylinders. It is a strong smelling compound and help in the detection of gas leakage. 

S7. Ans.(b)
Sol. Atoms are neutral. When an atom loses electron, it becomes positively charged and when an atom gains electron, it becomes negatively charged and when an atom gains electron, it becomes negatively charged. Hence, a body is charged negatively when it has  acquired some electrons from outside. 

S8. Ans.(d)
Sol. Titanium (Ti) metal is used for making boats because it does not corrode by the sea water. 

S9. Ans.(c)
Sol. Contact lenses are made from lucite. It is a polymer of methyl methacrylate. Th other names of lucite are plexiglass, acrylate and Perspex. 

S10. Ans.(a)
Sol. Water has a high specific heat. 


No comments