Question-ITI
Answer the following in short:
1. What was the contribution of Lavoisier to chemistry?
2. What is a monoatomic molecule?
3. What is the use of valency?
4. State the technique of separation used in winnowing,
Question-IV
Answer the following in details:
1. Describe the role of chemistry in agriculture.
2. State the characteristics of a molecule.
3. State the significance of the molecular formula of a compound with an example,
Answers
1. What was the contribution of Lavoisier to chemistry?
Answer :-
Antoine-Laurent Lavoisier, a meticulous experimenter, revolutionized chemistry. He established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions with what he named “oxygen,” and helped systematize chemical nomenclature, among many other accomplishments.
2. What is a monoatomic molecule?
A molecule composed of just one atom, and lacking any covalent bonds. The noble gases (He, Ne, Ar, Kr, Xe, and Rn) are all monoatomic, whereas most other gases are at least diatomic. Approximate Composition of the Atmosphere at the Earth's Surface.
3. What is the use of valency?
Valency helps to determine a chemical formula. It helps to determine how many atoms of an element will combine with another element to form any chemical formula.
4. State the technique of separation used in winnowing?
The techniques of separation used in winnowing are :-
chromatography: Involves solvent separation on a solid medium.
distillation: Takes advantage of differences in boiling points.
evaporation: Removes a liquid from a solution to leave a solid material.
filtration: Separates solids of different sizes.