Theoretical Fundamentals of Analytical Chemistry ✅

Question 1

What are the basic laws of stoichiometry?

Answer 1

✓ Law of Conservation of Mass
✓ Mass-energy Equivalence
✓ Law of Definite Proportions
✓ Law of Multiple Proportions
✓ Law of Combining Volumes
✓ Avogadro’s Law
✓ Law of Equivalent Proportions

Question 2

What is stoichiometry?

Answer 2

Stoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products in chemical reactions.

Question 3

What is the Law of Conservation of Mass?

Answer 3

In an isolated or closed system, the mass of reactants in the beginning must be equal to the mass of the products in the end.

Question 4

Who discovered the law of conservation of mass?

Answer 4

M. Lomonosov. and L. de Lavoisier

Question 5

What is the Mass-energy equivalence?

Answer 5

• A. Einstein
• neither mass nor energy are conserved separately,
• mass and energy can be traded one for the other and only the total “mass-energy” will be conserved.
• The relationship between the mass and the energy:
  E = mc2
  E- energy
  m- mass of the object
  c- velocity of light

Question 6

What is the law of definite proportions?

Answer 6

Every chemical compound contains fixed and constant proportions (by weight) of its constituent elements.

Question 7

Who came up with the law of definite proportions?

Answer 7

Proust

Question 8

What is the law of multiple proportions?

Answer 8

When the same two elements combine to form more than one compound: the ratios of the mass of one element in the first compound to its mass in the second compound, can always be expressed as ratios of small whole numbers (eg. 1:3 or 2:5).

Question 9

Who came up with the law of multiple proportions?

Answer 9

john dalton

Question 10

What is the Law of combining volumes?

Answer 10

When gases react, they do so in volumes which bear a simple ratio to one another, and to the volume of the product(s) formed if GASEOUS, provided the TEMPERATURE and PRESSURE remain constant.
- volume of gas in products = volume of gas in reactants

Question 11

Who came up with the law of combining volumes?

Answer 11

Joseph Louis Gay-Lussac

Question 12

What is the Avogadro’s law?

Answer 12

Equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules.

22.4 litres of any gas contains 6.023 · 10^23 number of molecules irrespective of its nature.

Question 13

Who came up withAvogadro’s law?

Answer 13

Amadeo Avogadro

Question 14

What is the law of equivalent proportions?

Answer 14

The proportions in which two elements separately combine with a third element are also the proportions in which they combine together.

m1/m2=e1/e2

m1, m2 – mass of reactants;
E1, E2 – equivalents of reactants.

Question 15

Who came up with the law of equivalent proportions?

Answer 15

john dalton

Question 16

What is a chemical equivalent?

Answer 16

The equivalent is formally defined as the amount of a substance which will either:
• REACT with or supply ONE MOLE OF H+ IONS in an acid-base reactions;
• REACT with or supply ONE MOLE OF ELECTRONS in a redox reactions.

Question 17

What is the historical definition of an equivalent?

Answer 17

The amount of a substance that will react with one gram of hydrogen, or with eight grams of oxygen and attaches or exchanges one mole of electrons.

Question 18

How is the element’s equivalence calculated? What are its units?

Answer 18

E=A/n

where:
A - element’s atomic mass;
n - element’s valence.

units: g/E
g/eq

Question 19

What is a compound equivalence? How is it calculated?

Answer 19

E=M/(n*v)

Where:
M - compound’s molar mass;
v - valence of atoms, ions, radicals, which participate(d) in the exchange reaction;
n - the number of these atoms, ions, radicals.

Question 20

What is oxider’s (reducer’s) equivalent?

Answer 20

E=M/e

Where:
M - compound’s molar mass;
e - attached by oxidizer or released by reducer electron number.

eg. E(KMnO4)= (39+55+(4 * 16))/5=31.6 g/eq

(Mn7+ + 5e- –> Mn2+)