Question

1. Briefly describe the structure of an atom.

2. Distinguish covalent, ionic, and hydrogen bonds.

3. Explain oxidation reduction reactions. How are they important in soils.

4. Talk about acid, bases, and buffering in soils.

Answer 1

Ans 1: Structure of an atom: Structure of an atom means that positively charged nucleus and positively charged electrons will be circled within an atom.First of all we need to know the type of atoms. Atoms consists of 3 particles:

• Protons:It is a subatomic particle denoted by p or p⁺. It has a positive electric charge.
• Electrons:It is a negatively charged subatomic particles.
• Neutrons: It is also particle with a neutral charge.

So, the middle of the atom contains the positively charged particle and the no charge particle.The number of protons is equal to the atomic number, and number of electrons is equal to the number of protons.The outermost part of the atom are also called electrons shell(positively charged).

Ans 2:

Difference between covalent ,ionic and hydrogen bonds

COVALENT BOND IONIC BOND HYDROGEN BOND 1.Sharing of electrons take place. 1.Loss or gains of electrons between two atoms. 1.Bonds with highly electronegative elements(F,O,N) 2. Intramolecular bonds. 2. Intramolecular bonds. 2. Intermolecular bonds. 3. One or more pairs of electrons are shared by two atoms. 3.One or more electrons are removed and attached to another atom. 3. Metallic bonding is hydrogen bonding. 4.The covalent bond is a strong bond. 4.Ionic bond is weaker than covalent but stronger than hydrogen bond. 4.The hydrogen bond is a weak bond. 5. Bond angle of covalent bond is 109.47 degree. 5. Bond angle of ionic bond is 180 degree. 5. Bond angle of hydrogen is 104.5 degree.

Ans 3: Oxidation reduction reactions: Oxidation means losing of electrons and reduction means gaining of electrons. When one electron is lost in a reaction than at the same one atom will also gain electron, it has to occur simultaneously.So, reaction involving oxidations and reductions are called redox reactions.Oxidation reduction reaction means in the given reaction both oxidation(loss of electrons) and reduction(gain of electron) will occur simultaneously. Redox reaction consist of two part, a reduced half and oxidised half.So, reduced half gains electrons and oxidation number decreases, and oxidised half loss electrons and oxidation number increases.This process is called oxidation reduction reactions. For example, in the given reaction iron atoms in ferric oxides lose oxygen atom to Al atoms, Producing Al₂O_3.

Fe₂O₃ + 2Al -----> Al₂O₃ + 2Fe

Oxidation reduction reaction is important in soils to prevent environmental problems. Environment problem is controlled by oxidation of the sulphides that contains some minerals and producing soil.

Ans 4: Acid: It is the proton donor and it has capability of forming covalent bond. Acids have a pH less than 7 and it turns blue litmus paper red.Acids usually react with metal to form salts and contains hydrogen ions. It conduct electricity when dissolved in water and react with metal to form hydrogen gas.

Base: It is substance in aqueous solution that produce hydroxide ion when dissolved in water such as NaOH,KOH etc.Base have a pH greater than 7 and it turns red litmus paper blue.It is ionic compounds which produce negative hydroxide ions when dissolved in water.It also conduct electricity when dissolved in water and it has bitter taste.

Buffering in soils: Buffering refers to change in pH(acid or base). In soil buffering, soil can stop the nutrient or pH changes by absorption.Higher buffer means that soil can absorb more acid or base without a significant change.Lower buffer means that pH can be recovered faster with the application compared to clay soils.