Question

Subject ⇝ Chemistry
Class ⇝ 8
Topic ⇝ Hydrogen

$\sf{\bf{\quad{(A) Give Reasons (Word limit 20 to 40).}}}$

1. In laboratory preparation of hydrogen gas, the gas is collected by the downward displacement of water.

2. When sodium reacts with water, some flames are seen on the surface of water.

3. Hydrogen is used as a reducing agent.
_______________________________
$\sf{\bf{\quad{(B) Answer the questions.}}}$

1. Elaborate the statement - $\bf{Hydrogen is reducing agent.}$

2. Explain the use of hydrogen on the basis of:-

(i) As fuel.
(ii) Extraction of metals.
(iii) Meteorological balloons.
(iv) Hydrogenation of oil.
==================================


Thank you!
​

Answer 1

Answer:

1.

Hydrogen is collected by downward displacement of water as it is less denser than water. Hence it comes out at the surface of water . It is insoluble in water so it does not dissolve in water.

2.

Answer: metals like sodium react with water to give hydrogen. These metal float on the surface of water and catch fire. sodium gives a golden yellow coloured flame.

3.

Hydrogen gas is a reducing agent when it reacts with non-metals and an oxidizing agent when it reacts with metals. ... Hydrogen acts as a reducing agent because it donates its electrons to fluorine, which allows fluorine to be reduced.

4.

Nearly all of the hydrogen consumed in the United States is used by industry for refining petroleum, treating metals, producing fertilizer, and processing foods. U.S. petroleum refineries use hydrogen to lower the sulfur content of fuels.

Explanation:

please Mark my answer in brainlist plz

Answer 2

Answer: ( pls add as brainlist )

a) 1 Hydrogen is collected by downward displacement of water as it is less denser than water. Hence it comes out at the surface of water . It is insoluble in water so it does not dissolve in water. In case of displacement with air, it is not possible even if hydrogen is lighter than air (14.5 times lighter than air).

2) Answer: metals like sodium react with water to give hydrogen. These metal float on the surface of water and catch fire. sodium gives a golden yellow coloured flame

3) Hydrogen gas is a reducing agent when it reacts with non-metals and an oxidizing agent when it reacts with metals. ... Hydrogen acts as a reducing agent because it donates its electrons to fluorine, which allows fluorine to be reduce

Explanation:

b) 1) Hydrogen gas is a reducing agent when it reacts with non-metals and an oxidizing agent when it reacts with metals. ... Hydrogen acts as a reducing agent because it donates its electrons to fluorine, which allows fluorine to be reduced.

2) i) Fuel cells can produce electric power from sustainable sources.

Hydrogen used to fuel the cells can itself be produced using electrolysis systems powered by solar panels or wind turbines.

2) The hydrogen can be produced and stored at any time so now there is a method of storing solar and wind energy as hydrogen fuel.

ii)

Answer: In addition to reducing the mobility of dislocations, solute hydrogen can also react, either with the solvent metal to form a hydride, or with some other solute element to form a new phase.

iii)

Hydrogen is another gas lighter than air; it's even lighter than helium. Hydrogen, however, is not used in balloons and this demonstration shows why. ... This is because hydrogen burns very easily. It combines with oxygen to make water vapor.

iv) Hydrogenation of oil

Oils (such as vegetable, olive, sunflower) are liquids at room temperature. In the food industry, hydrogen is added to oils (in a process called hydrogenation) to make them more solid, or 'spreadable'. ... The use of hydrogenated helps to prolong the shelf-life of the food and maintain flavour stability.