All questions of Class 10 NCERT Chemistry for OPSC OCS (Odisha) Exam

There were 63 known elements in 1860 when Mendeleev published his Periodic Table. CIENTISTS HAD IDENTIFIED over 63 elements by Mendeleev's time. 

Although metals are supposed to be good conductors of electricity and heat,metals like mercury, lead, alloys of iron and chromium, titanium and stainless steel are poor conductors when compared to silver, copper and gold.

Reactivity Series:

The reactivity series is a list of metals arranged in order of their decreasing reactivity. The most reactive metal is placed at the top and the least reactive metal is placed at the bottom of the series.

The reactivity series of metals is as follows:

Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Lead > Copper > Silver > Gold

Explanation:

Aluminium is more reactive than zinc and is placed above zinc in the reactivity series. This is because aluminium has a stronger tendency than zinc to lose electrons and form positive ions.

When aluminium is exposed to air, it reacts with oxygen to form a layer of aluminium oxide. This layer of oxide is very thin and is also very stable. It prevents further reaction of aluminium with oxygen and protects the metal from corrosion.

Zinc, on the other hand, reacts with oxygen in the air to form zinc oxide. However, the layer of oxide formed on zinc is not as stable as the layer of oxide formed on aluminium. Therefore, zinc is more susceptible to corrosion than aluminium.

Conclusion:

In conclusion, aluminium is more reactive than zinc and is placed above zinc in the reactivity series. This means that aluminium can displace zinc from its compounds in a chemical reaction, but zinc cannot displace aluminium from its compounds.

The functional group is ketone (> C = 0) also known as alkanone.     

Because it more fastly or quickly loss it's electron.

Acetic acid...

Most Abundant Non-Metal on Earth:

Explanation:
Oxygen is the most abundant non-metal on Earth. It makes up around 21% of the Earth's atmosphere, and it is also found in the Earth's crust, oceans, and other compounds like water and rocks. Oxygen is essential for life as it is a key component of the air we breathe and is necessary for the respiration of living organisms.

Other Options:
Let's take a look at the other options and why they are not the most abundant non-metal on Earth:

a) Sulphur - Sulphur is a non-metal, but it is not the most abundant on Earth. Although it is found in large quantities in the Earth's crust and oceans, it is not as abundant as oxygen.

c) Silicon - Silicon is a non-metal that is found in the Earth's crust, but it is not as abundant as oxygen. It is often found in rocks and minerals like quartz and sand, but it is not as essential to life as oxygen.

d) Phosphorus - Phosphorus is a non-metal that is found in the Earth's crust, but it is not as abundant as oxygen. It is often used in fertilizers and is an important component of DNA, but it is not as essential to life as oxygen.

Conclusion:
In conclusion, oxygen is the most abundant non-metal on Earth. It is essential for life and is found in the Earth's atmosphere, crust, oceans, and other compounds.

Silver is best conductor of heat while among metals lead is poorest conductor of heat. Cooper and aluminum are good conductor while mercury is a poor conductor. Although metals are supposed to be good conductors of electricity and heat,metals like mercury, lead, alloys of iron and chromium, titanium and stainless steel are poor conductors.

This is a natural indicator which are found in the nature of the plants

Acidity and Basicity of Oxides:

Oxides are binary compounds of oxygen with another element. Depending on the nature of the element, oxides can be acidic, basic, amphoteric or neutral.

Acidic Oxides:

Acidic oxides are oxides of non-metals. They react with water to form acids. For example:

1. CO2 + H2O → H2CO3 (Carbon dioxide dissolves in water to form carbonic acid)

2. SO2 + H2O → H2SO3 (Sulphur dioxide dissolves in water to form sulphurous acid)

3. NO2 + H2O → HNO3 (Nitrogen dioxide dissolves in water to form nitric acid)

4. P4O10 + 6H2O → 4H3PO4 (Phosphorus pentoxide dissolves in water to form phosphoric acid)

Basic Oxides:

Basic oxides are oxides of metals. They react with water to form bases. For example:

1. Na2O + H2O → 2NaOH (Sodium oxide dissolves in water to form sodium hydroxide)

2. MgO + H2O → Mg(OH)2 (Magnesium oxide dissolves in water to form magnesium hydroxide)

3. CaO + H2O → Ca(OH)2 (Calcium oxide dissolves in water to form calcium hydroxide)

Amphoteric Oxides:

Amphoteric oxides are oxides that can act as both acidic and basic depending on the nature of the reacting species. For example:

1. Al2O3 + 6HCl → 2AlCl3 + 3H2O (Aluminium oxide reacts with hydrochloric acid to form aluminium chloride and water)

2. ZnO + 2HCl → ZnCl2 + H2O (Zinc oxide reacts with hydrochloric acid to form zinc chloride and water)

Neutral Oxides:

Neutral oxides are oxides that do not react with water to form either an acid or a base. For example:

1. CO (Carbon monoxide)

2. N2O (Nitrous oxide)

3. NO (Nitric oxide)

Conclusion:

Mostly oxides of non-metals are acidic in nature as they react with water to form acids. Hence, the correct answer is option 'D'.