Theoretical basics of Inorganic chemistry

Q1. Who established the two important laws of chemical combinations?

Answer: Antoine L. Lavoisier and Joseph L. Proust

 

Q2. What are the laws of chemical combinations?

Answer: These are group of laws which describe how different elements and compounds combine together to form new compounds. Most of these were established based on chemical experimental results. These laws are:

1.      Law of Conservation of Mass

2.      Law of Constant composition

3.      Law of Multiple proportions

4.      Law of reciprocal proportions

5.      Law of Combining Volumes ( Gay Lussac’s law of Gaseous volumes )

 

Q3. What are the three subatomic particles? Where is each located? What is each one's charge?

Answer. The three subatomic particles are the proton, neutron, and electron. The proton and the neutron are located inside the nucleus of the atom. The proton is positively charged and has a significant mass that is used to calculate an atom's mass number. The neutron is neutrally charged and like the proton, has a significant mass that is also a part of an atom's mass number. The electrons are located outside the nucleus inside orbitals. Electrons are negatively charged and have negligible mass. Thus, the mass of the electrons is ignored when calculating the atom's mass number.

 

Q4. Give a brief summary of John Dalton's theory of the atom.

Answer: Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements. Compounds are composed of atoms of more than one element in whole number ratios with each other. A chemical reaction involves only the separation, combination, or rearrangement of atoms, not their creation or destruction.

 

Q5. What is the Law of Conservation of Mass and what does it mean?

Answer: This law states that matter can be neither created nor destroyed. Atoms are unchanged during a chemical reaction. If an atom, which has specific mass, exists before a reaction occurs, it also exists after a reaction occurs. This means that during the course of a reaction, mass is also conserved.

 

Q6. Proposed Law of definite Proportions (or Law of Constant Compositions)?

Answer: J.L. Proust 1779 (French Chemist)

 

Q7. What is an atom?

Answer: An atom is the smallest particle of an element which takes part in chemical reactions. An atom is considered to be building blocks of matter

 

Q8. What is an ion?

Answer: An ion is positively or negatively charged atom or group of atoms. There are two types of ions:

1.      Cations (positively charged ions) e.g. Na⁺, K⁺, Cu²⁺

2.      Anions (negatively charge ion) e.g. Cl^-, SO₄^2-

 

Q9. What is the molecular mass of a substance?

Answer: The average mass of a molecule of a substance expressed in atomic mass units is called its molecular mass.

It is obtained by adding together the atomic masses of all the atoms  presents in one molecule of the substance.

 

Q10.  Is the atomic weight for each element a single exact value? Please explain.

Answer: No, because each element can have different isotopes, meaning the number of neutrons can vary. Because each isotope has a different number of neutrons it also has a different atomic weight. The atomic weight shown on a periodic table is the average atomic weight that takes into consideration the natural abundance of each isotope.

 

Q11. How is a molecule different than a compound?

Answer: A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements.

 

Q12. When you charged a strip of plastic by rubbing it through your fingers or on cloth, you actually transferred electrons onto the plastic strip. Using the terms “electrons” and “protons”, and “negative” and “positive”, explain why the strip was attracted to your fingers or the cloth you rubbed it on.

Answer: If electrons were transferred to the plastic, the plastic has extra electrons and becomes negative, since electrons are negative. If my fingers lost electrons, they would have more protons than electrons and become positive. Positive and negative attract.