Tag: water resources and conservation

Questions Related to water resources and conservation

Find the number of molecules of water in $CoCl _2$?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. 3

  2. 4

  3. 5

  4. 6

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Correct Option: D
Explanation:

The number of molecules of water in $CoCl _2$ is 6. So the formula becomes $CoCl _2.6H _2O$.

Which of the following does not contain impurities?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. Rain water

  2. Distilled water

  3. Both A and B

  4. None of above

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Correct Option: C
Explanation:

Rain water and distilled water does not contain impurities.

Distilled water is water that has had many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.

 Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then precipitated, that it become heavy enough to fall under gravity. Rain i
s a major component of the water cycle and is responsible for depositing most of the fresh water on the earth. It does not contain any impurities. 

For $\displaystyle 4{ NH } _{ 3 }\left( g \right) +5{ O } _{ 2 }\left( g \right) \rightarrow 4NO\left( g \right) +6{ H } _{ 2 }O\left( g \right) $, if you begin with 16.00 g ammonia and excess oxygen, how many grams of water will be obtained?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. 2.294

  2. 36.51

  3. 1.409

  4. 25.3

  5. 2.513

Show answer
Correct Option: D
Explanation:

The molecular weights of ammonia and water are 17 g/mole and 18 g/mole respectively.
4 moles of ammonia gives 6 moles of water.
$4 \times 17 = 68$ g of ammonia will give $6 \times 18 = 108$ g of water.
16.00 g of ammonia will give $16.00 \times \dfrac {108}{68} = 25.3$ g of water.

For $\displaystyle 4{ NH } _{ 3 }\left( g \right) +5{ O } _{ 2 }\left( g \right) \rightarrow 4NO\left( g \right) +6{ H } _{ 2 }O\left( g \right) $, if you begin with 66.00 g ammonia and 54.00 g oxygen, how many grams of water will be obtained?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. 2.294

  2. 36.51

  3. 1.409

  4. 25.3

  5. 2.513

Show answer
Correct Option: B
Explanation:

The molecular weights of ammonia, oxygen and water are 17 g/mole, 32 g/mole and 18 g/mole respectively.

66.00 g ammonia $= \dfrac {66.00}{17} = 3.88$ moles ammonia.
54.00 g oxygen $=\dfrac {54.00}{32.0}=1.6875$ moles oxygen.
4 moles ammonia reacts with 5 moles oxygen.
Hence, 3.88 moles ammonia will react with $3.88 \times \dfrac {5}{4} = 4.85$ moles oxygen but only 1.6875 moles oxygen are present. Hence oxygen is the limiting reagent.

5 moles of oxygen gives 6 moles of water.
1.728 moles of oxygen will give $1.6875 \times \dfrac {6}{5} = 2.025$ moles of water.
The mass of water obtained is $18 \times 2.025 = 36.51$ g of water.

Dissolved salts in water are important because :

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. they provide taste

  2. growth of plants

  3. minerals essential for body

  4. all of the above

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Correct Option: D
Explanation:

Dissolved salts in water are important because
(A) They provide taste
(B) Growth of plants
(C) Minerals essential for body
Water contains dissolved salts which provide taste to water for drinking purposes. Also these salts are essential for growth and development of plants. These dissolved salts provide the essential minerals which are required for growth of body.

Dissolved gases can be removed from water by:

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. chlorination

  2. boiling

  3. filtration

  4. both A and C

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Correct Option: B
Explanation:

Dissolved gases can be removed from water by boiling.
Water contains certain gases in dissolved state. The higher the temperature of a solution becomes, the less a gas dissolves provided it doesn't react with the solvent. Consequently, heating/boiling a solution can expel the remaining gas.

How many grams of water can be produced when 8 g of hydrogen react with 8 g oxygen?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. 8 g

  2. 9 g

  3. 18 g

  4. 27 g

  5. 30 g

Show answer
Correct Option: B
Explanation:
The molecular masses of hydrogen, oxygen and water are 2 g/mole, 32 g/mole and 18 g/mole respectively.
$2H _2 + O _2 \rightarrow 2H _2O$
 $2 \times 2 = 4$ g of hydrogen reacts with  $1 \times 32 = 32$ g of oxygen to form  $2 \times 18 = 36$ g of water.
Hence, $\dfrac {4}{4} = 1$ g of hydrogen reacts with  $\dfrac {32}{4}  = 8$ g of oxygen to form  $\dfrac {36}{4}= 9$ g of water.

9 grams of water can be produced when 8 g of hydrogen reacts with 8 g oxygen.

The colour of anhydrous $CoCl _2$ is:

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. pink

  2. blue

  3. red

  4. white

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Correct Option: B
Explanation:

Anhydrous $CoCl _2$ is blue in colour.


As it absorbs water, it turns pink.

Hence,option B is correct.

The discovery of the fact that oxygen and hydrogen combine to form water, was a major step in the development of science. Who made this discovery?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. Carl Wilhelm Scheele

  2. Isaac Newton

  3. Joseph Priestley

  4. Henry Cavendish

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Correct Option: D
Explanation:
It was the chemist Henry Cavendish (1731 – 1810), who discovered the composition of water when he experimented with hydrogen and oxygen and mixed these elements together to create an explosion (oxyhydrogen effect). In 1811, the Italian physician Amadeo Avogadro finally found the ${H} _{2}O$ formula for water.

What is the final product when oxygen and hydrogen are mixed in a test tube at room temperature?

evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

  1. Hydrogen peroxide

  2. Water

  3. A base

  4. A zwitterion

  5. No reaction takes place

Show answer
Correct Option: E
Explanation:

The gas-phase oxidation of hydrogen has been extensively studied over a wide range of temperatures and pressures.


$H _2 + \dfrac {1}{2} O _2 \rightarrow H _2O$ ,$ \Delta H^o= -242 kj/mol$
$H _2(g) + \dfrac {1}{2}O _2(g) \rightarrow H _2O(g) $        $\Delta H^o = –242 kJ/mol$

This reaction does not take place at all when the two gases are simply mixed at room temperature. 

At temperatures around 500-600°C it proceeds quite smoothly, but when heated above 700° or ignited with a spark, the mixture explodes.

Hence the correct option is E.