Chemistry Questions

An ionic bond is a chemical bond between two atoms in which one atom seems to donate its electron to another atom.

Here in the given compounds, the compound that contains ionic bond is CaO, Calcium oxide.

A redox reaction is a type of reaction which involves transfer of electrons among two species. This reaction is also called oxidation-reduction reaction.

In oxidation process, there is an increase in oxidation state of an atom, ion or molecule by losing the electrons.

In reduction process, there is a decrease in oxidation state of an atom, ion or molecule by accepting the electrons.

1)

In this reaction, Ba undergoes oxidation and Cl undergoes reduction.
This reaction is redox reaction.
In this reaction, oxidation number of Ba increases from 0 to +2 . So, Ba undergoes oxidation. The oxidation number of Cl decreases from 0 to -1. So, Cl undergoes reduction.

2) 

From this above reaction, it is clear that Aluminum undergoes oxidation and silver undergoes reduction.
Due to this, this reaction is redox reaction.

In this reaction, oxidation number of Aluminum increases from 0 to +1. So, aluminum undergoes oxidation. The oxidation number of silver decreases from +1 to 0. So, silver undergoes reduction.

3)

In this reaction, Mg undergoes oxidation and Br undergoes reduction.
This reaction is redox reaction.
The reactions 1, 3 and 4 are redox reactions.
In this reaction, oxidation number of Mg increases from 0 to +2 . So, Mg undergoes oxidation. The oxidation number of Br decreases from 0 to -1 . So, Br undergoes reduction.

Hence all the above reactions are redox reactions.

Electronegativity, is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself.

Activation energy is a minimum amount of energy that required for the chemical reaction to happen or to take place.

S8 is an elemental form of sufur. In elemental form it can't be reduced or oxidized. Hence, it oxidation number is zero and thus sulfur is zerovalent here.

Compounds are substances is true about them.

Many toxic gases along with water vapour are emitted in vocanic eruptions. All such toxic gases include hydrochloric acid, sulfur dioxide, carbon dioxide, hydrogen sulfide and carbon monoxide. Methane is not produced in the volcanic eruptions.

Most of the ozone in the atmosphere is found in the layer of stratosphere, which begins about 10.16 kilometers (6.10 miles) above Earth's surface and extends up to about 50 kilometers (31 miles) altitude.