Tag: importance of water

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

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?

  1. 2.294

  2. 36.51

  3. 1.409

  4. 25.3

  5. 2.513
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Dissolved salts in water are important because :

  1. they provide taste

  2. growth of plants

  3. minerals essential for body

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Dissolved gases can be removed from water by:

  1. chlorination

  2. boiling

  3. filtration

  4. both A and C
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. 8 g

  2. 9 g

  3. 18 g

  4. 27 g

  5. 30 g
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

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?

  1. Carl Wilhelm Scheele

  2. Isaac Newton

  3. Joseph Priestley

  4. Henry Cavendish
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

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

  1. Hydrogen peroxide

  2. Water

  3. A base

  4. A zwitterion

  5. No reaction takes place
Reveal answer Fill a bubble to check yourself
E Correct answer
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.