1. An element X has four electrons in its outermost orbit. What will be the formula of its compounds with Hydrogen?
(a) X4H
(b) X4H4
(c) XH3
(d) XH4
[43rd B.P.S.C. (Pre) 1999]
Ans. (d) XH4
- Element X combined with four electrons in its outermost layer will be XH4.
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2. According to weight, the percentage of Hydrogen in water (H2O), is –
(a) 44.45 %
(b) 5.55 %
(c) 88.89 %
(d) 11.11 %
[Uttarakhand U.D.A./L.D.A. (Mains) 2006]
Ans. (d) 11.11 %
- The percentage of any element in a compound is calculated by the mass of that element divided by the total mass of the compound.
- In water (H2O), there are two hydrogen atoms.
- This means that 11.11% of the total mass of water is hydrogen.
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3. One mole of hydrogen gas burns in excess of oxygen to give 290 KJ of heat. What is the amount of heat produced when 4g of Hydrogen gas is burnt under the same conditions?
(a) 145 Kj
(b) 290 Kj
(c) 580 Kj
(d) 1160 Kj
[I.A.S. (Pre) 1994]
Ans. (c) 580 Kj
- 1 Mole of H2(Hydrogen) = 2 gm
- ∴ The energy released by 4 gm ∑ 290×2 = 580 Kj
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4. Burning of hydrogen produces –
(a) Oxygen
(b) Ash
(c) Soil
(d) Water
[47th B.P.S.C. (Pre) 2005]
Ans. (d) Water
- Hydrogen gas is very flammable and can burn in air from 4% to 75% of the air’s volume.
- However, it cannot burn without oxygen, and when it does burn with oxygen it produces water.
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5. Which one of the following fuels causes minimum air pollution?
(a) Kerosene oil
(b) Hydrogen
(c) Coal
(d) Diesel
[U.P. Lower Sub. (Pre) 2015]
Ans. (b) Hydrogen
- Hydrogen is the cleanest type of fuel that can be burned. When it is burned, it only creates water.
- Coal, kerosene oil, and diesel are all called fossil fuels, and they create Carbon Dioxide and other bad gases when they are burned.
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6. Heavy water is a type of –
(a) Coolant
(b) Moderator
(c) Ore
(d) Fuel
[U.P.P.C.S. (Pre) 1993]
Ans. (a) & (b) Coolant & Moderator
- Heavy water, also called deuterium oxide (D2O), is used in nuclear reactors as a moderator and a coolant.
- It works well because it slows down neutrons and doesn’t absorb them easily.
- Deuterium is a type of hydrogen that has a neutron and a proton.
- It combines with oxygen to form the heavy water.
- Normal water (H2O) also acts as a moderator and coolant in nuclear reactors.
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7. The chemical formula of Heavy Water is :
(a) H2O
(b) D2O
(c) H2CO3
(d) H2S
[Jharkhand P.C.S. (Pre) 2003]
Ans. (b) D2O
- Heavy water, also known as deuterium oxide, is used in nuclear reactors to help slow down neutrons and keep things cool.
- It is effective at doing this because it doesn’t absorb neutrons very easily.
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8. The chemical formula for heavy water is :
(a) H2O
(b) N2O
(c) D2O
(d) CuO
(e) None of the above/More than one of the above
[66th B.P.S.C. (Pre) (Re. Exam) 2020]
Ans. (c) D2O
- Deuterium oxide, also known as heavy water, is used in nuclear reactors because it slows down neutrons and doesn’t easily absorb them.
- Deuterium is a type of hydrogen with an extra neutron.
- It combines with oxygen to form heavy water.
- Regular water is also used in these reactors.
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9. The substance used as moderator and coolant both, in nuclear reactors is :
(a) Ordinary water
(b) Heavy water
(c) Liquid Ammonia
(d) Liquid Hydrogen
[U.P. P.C.S. (Pre) 2016]
Ans. (a) & (b) Ordinary water & Heavy water
- Deuterium oxide, also known as heavy water, is used in nuclear reactors as a moderator and coolant.
- This is because it is made of an isotope of hydrogen which has both a proton and a neutron, and it slows down neutrons very efficiently and doesn’t absorb them very often.
- Normal water (H2O) can also be used in nuclear reactors for the same reasons.
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10. What is heavy water?
(a) Oxygen + Heavy Hydrogen
(b) Hydrogen + Oxygen
(c) Hydrogen + New Oxygen
(d) Heavy Hydrogen + Heavy Oxygen
[M.P.P.C.S. (Pre) 1991]
Ans. (a) Oxygen + Heavy Hydrogen
- Heavy water is water that has heavy hydrogen (deuterium) instead of regular hydrogen.
- It can also be referred to as 2H2O or D2O.
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11. Heavy water is that water –
(a) The temperature of which is kept constant at 4°C
(b) In which insoluble salts of Calcium and Potassium are present
(c) In which isotopes takes place of Hydrogen
(d) In which isotopes takes place of Oxygen
[41st B.P.S.C. (Pre) 1996]
Ans. (c) In which isotopes takes place of Hydrogen
- Heavy water is a type of water made of deuterium which has two times the mass of regular hydrogen, and oxygen.
- Normal water is made of hydrogen and oxygen (H2O).
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12. Heavy water –
(a) Contains more dissolved air
(b) Contains deuterium in place of Hydrogen
(c) Contains more dissolved minerals and salts
(d) Contains organic impurities
[U.P.P.C.S. (Mains) 2007]
Ans. (b) Contains deuterium in place of Hydrogen
- Heavy water is made up of two different kinds of hydrogen – deuterium which is twice as heavy as normal hydrogen, and oxygen.
- Normal water has hydrogen and oxygen (H2O).
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13. Who among the following discovered heavy water?
(a) Heinrich Hertz
(b) H.C. Urey
(c) G.Mendel
(d) Joseph Priestly
[I.A.S. (Pre) 2008]
Ans. (b) H.C. Urey
- Harold Clayton Urey, an American chemist, found deuterium and heavy water in 1931 and got a Nobel Prize in Chemistry in 1934 due to this discovery.
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14. Heavy water has molecular weight :
(a) 18
(b) 20
(c) 36
(d) 54
[U.P. Lower Sub. (Mains) 2015]
Ans. (b) 20
- Heavy water, also known as deuterium oxide, has a different type of hydrogen atom than regular water.
- The hydrogen atom in heavy water has twice the mass of the hydrogen atom in regular water, making its molecular weight about 20, compared to regular water’s molecular weight of 18.
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15. Consider the following statements: Hard water is not suitable for
1. Drinking
2. Washing clothes with soap
3. Use in boilers
4. Irrigating crops
Which of these statements are correct?
(a) 1 and 2
(b) 2 and 3
(c) 1, 2 and 4
(d) 1, 2, 3 and 4
[I.A.S. (Pre) 2000]
Ans. (d) 1, 2, 3 and 4
- Hard water has a high concentration of minerals, such as calcium and magnesium sulfate and chloride.
- It has a salty taste and is not suitable for drinking.
- It is difficult to clean with hard water as it takes more soap and the residue left behind is hard to remove.
- Boiling hard water at home or in industries will leave behind deposits of calcium and magnesium salt, which can reduce the efficiency of boilers, kettles, and pipes, and cause blockages or even explosions.
- If there is a high salt content in irrigation water, plants are unable to take up the water, even if the soil is moist, as the hard water blocks the Xylem tissues.
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16. Permanent hardness of water is due to –
(a) Chlorides and sulfates of Calcium and Magnesium
(b) Calcium bicarbonate sulfates
(c) Magnesium bicarbonate
(d) Chlorides of Silver and Potassium
[Uttarakhand P.C.S. (Pre) 2005, 40th B.P.S.C. (Pre) 1995]
Ans. (a) Chlorides and sulfates of Calcium and Magnesium
- Hard water is not safe to drink and has a lot of calcium and magnesium salts in it.
- It’s difficult to wash clothes with hard water because it needs more soap and leaves a residue that’s hard to get out.
- Boiling hard water can clog pipes and boilers and make them less effective.
- If the salt levels in irrigation water is too high, it will be hard for plants to get water even if the soil is moist. Hard water is not suitable for irrigation because it blocks the Xylem tissues of plants.
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17. The pH value for water is –
(a) Nearly zero
(b) Nearly 7
(c) 5 or less than 5
(d) 8.7 or more
[Uttarakhand P.C.S. (Pre) 2005]
Ans. (b) Nearly 7
- Pure water has a pH of 7, which means it is neutral.
- When the pH is lower than 7, the solution is considered acidic and when the pH is higher than 7, the solution is considered basic or alkaline.
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18. The pH value of water is
(a) 4
(b) 7
(c) 12
(d) 18
(e) None of the above/More than one of the above
[66th B.P.S.C. (Pre) (Re. Exam) 2020, 65th B.P.S.C. (Pre) 2019]
Ans. (b) 7
- Pure water has a pH of 7, which makes it neither acidic nor basic.
- Solutions that are lower than 7 on the pH scale are considered acidic, while solutions higher than 7 are basic or alkaline.
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19. Which is the purest form of water?
(a) Tap water
(b) Seawater
(c) Rainwater
(d) Distilled water
[M.P.P.C.S. (Pre) 2000]
Ans. (c) Rainwater
- Rainwater is the cleanest type of water.
- The water on the ground has been contaminated with alkaline and acidic substances, making it dirty.
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20. Water is a good solvent of ionic salts because –
(a) It has a high boiling point
(b) It has a high dipole moment
(c) It has a high specific heat
(d) It has no color
[I.A.S. (Pre) 1994]
Ans. (b) It has a high dipole moment
- Water can dissolve many things because it has a special kind of charge.
- This charge helps it bond with compounds that also have a charge, such as with salt.
- For example, when salt is added to water, the water molecules form a bond with the sodium and chloride ions, which makes the salt dissolve.
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21. Water can dissolve more substances than any other liquid because :
(a) it is dipolar in nature
(b) it is a good conductor of heat
(c) it has a high value of specific heat
(d) it is an oxide of hydrogen
[I.A.S. (Pre) 2021]
Ans. (a) it is dipolar in nature
- Water is a good solvent due to its polarity (it is dipolar in nature) and high dipole moment which can easily dissolve polar compounds.
- Water dissolves ionic salts by hydrating their component ions.
- For example, water dissolves NaCl by hydrating and stabilizing the Na+ and Cl– ions.
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22. Large quantities of drinking water is prepared from impure water by –
(a) Desalination
(b) Distillation
(c) Ion-exchange
(d) Decantation
[Uttarakhand P.C.S. (Pre) 2005]
Ans. (a) Desalination
- Desalination is a process that takes out salts and minerals from salty water.
- This process is done to make the water drinkable or usable for irrigation.
- Desalinating seawater is an effective way of making water that can be used for drinking, irrigation, and industrial purposes.
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23. Which gas is used in the purification of drinking water?
(a) Helium
(b) Chlorine
(c) Fluorine
(d) Carbon dioxide
[Jharkhand P.C.S. (Pre) 2013]
Ans. (b) Chlorine
- Chlorine is used to clean and purify water, such as in water treatment plants, as well as to kill germs in drinking water and public pools.
- It is an essential chemical for these processes.
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24. By which process the seawater can be converted into pure water?
(a) Deliquescence
(b) Efflorescence
(c) Electric separation
(d) Reverse osmosis
[R.A.S./R.T.S.(Pre) 2008]
Ans. (d) Reverse osmosis
- Reverse osmosis is a method used to make drinking water cleaner.
- It uses a special membrane to remove bigger pieces from the water.
- It is often used to make seawater or salty water into pure water.
- To do this, salty water and pure water are put on opposite sides of a membrane.
- If pressure is applied to the salty water side, the water will move the other way and will become clean.
- This process can take out bacteria and other particles from the water and is used in industries and to make pure water for people to drink.
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25. The process used for transforming salty water into pure water is called –
(a) Deliquescence
(b) Efflorescence
(c) Electric separation
(d) Reverse osmosis
[U.P.P.C.S. (Mains) 2013]
Ans. (d) Reverse osmosis
- Reverse osmosis (RO) is a water purification technology that uses a special filter to take out larger particles from drinking water.
- It is mainly used to turn salty water into fresh, clean drinking water.
- To do this, the salty water is placed on one side of a special filter, while pure water is placed on the other side.
- Then, a high pressure is applied to the salty water side of the filter, which causes the water to flow in the opposite direction.
- This produces pure water.
- Reverse osmosis can also remove bacteria and other molecules from solutions, and it is used in both industry and to produce potable water.
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26. By which process, Alum cleans the muddy water?
(a) Absorption
(b) Adsorption
(c) Coagulation
(d) Dialysis
[R.A.S./R.T.S.(Pre) 2000]
Ans. (c) Coagulation
- Alum (aluminum sulfate) is added to the water to make the tiny particles in the water stick together.
- This is called coagulation.
- The particles in the water can be between 5 mm and 1mm, or bigger than 0.5mm.
- The alum helps the particles stick together and sink to the bottom of the water.
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27. The gas used in the manufacture of Vanaspati Ghee from Vanaspati Oil is –
(a) Hydrogen
(b) Oxygen
(c) Nitrogen
(d) Carbon dioxide
[60th to 62nd B.P.S.C. (Pre) 2016,U.P.P.C.S. (Mains) 2013]
Ans. (a) Hydrogen
- Hydrogen gas is used to make vanaspati ghee.
- This process is known as hydrogenation.
- It involves passing hydrogen gas through vegetable oils under 8-10 atmospheric pressure with nickel powder (a catalyst) at a temperature of 150-180o C.
- This causes the oil to change into a solid fat called vanaspati ghee.
- Hydrogenation is a process where unsaturated compounds mix with hydrogen with the help of a catalyst and other suitable conditions and become saturated compounds.
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28. Which one of the following catalysts is used in the hydrogenation of vegetable oils?
(a) Zinc
(b) Platinum
(c) Nickel
(d) Iron
[U.P. P.C.S. (Mains) 2016, U.P.P.C.S. (Mains) 2010]
Ans. (c) Nickel
- Hydrogen gas is used to make vanaspati ghee.
- This process, called hydrogenation, happens when vegetable oils are mixed with hydrogen gas, nickel powder (acting as a catalyst), and heated to 150-180°C under 8-10 atmospheric pressure.
- This turns the oils into solid fat, which is known as vanaspati ghee.
- Hydrogenation is when unsaturated compounds are mixed with hydrogen and a catalyst under the right conditions and are changed to saturated compounds.
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