Some Basic Concept in Chemistry Formula: Definition, Questions, Examples

Outline of Basic Chemistry Concepts

The basics of chemistry deal with some principles according to which matter is governed. Some of the important definitions includes that of matter, which states any substance possessing mass and occupying space refers to matter, and element, which is a pure substance comprising atoms of only one kind. Also, compounds result from a combination of two or more elements in fixed ratios, such as water (H₂O) or even sodium chloride (NaCl).

Another core definition is that of mole, it may be described as a unit used to measure the magnitude of the substance; one mole is 6.022×10²³ entities. It tells us the number of particles in a mole is equal to the constant referred to as Avogadro's number, and it provides a practical application in the real world. Another mandate of chemistry is the law of mass conservation, which states that mass is neither created nor destroyed in a chemical reaction. Consequently, chemical equations must be balanced. From the above simple concepts, more sophisticated studies in chemistry can be created.

Heating of Carbonates

• Group II metal carbonates like MgCO₃, CaCO₃ and other bivalent metal carbonates (PbCO₃, ZnCO₃) liberate CO₂ on heating and leave their oxide as residue

$\mathrm{MCO}_3 \xrightarrow{\Delta} \mathrm{MO}+\mathrm{CO}_2$

• Group 1 metal carbonates like Na₂CO₃, K₂CO₃ are resistant to decomposition upon heating (except Li)

Heating of Bicarbonates

• Group II metal bicarbonates like Ca(HCO₃)₂ liberate CO₂ and H₂O on heating and leave their oxide as residue

$\mathrm{M}\left(\mathrm{HCO}_3\right)_2 \xrightarrow{\Delta} \mathrm{MO}+2 \mathrm{CO}_2+\mathrm{H}_2 \mathrm{O}$

• Group I metal bicarbonates like NaHCO₃ liberate CO₂ and H₂O on heating and leave their carbonate as residue

$2 \mathrm{Na}\left(\mathrm{HCO}_3\right) \xrightarrow{\Delta} \mathrm{Na}_2 \mathrm{CO}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O}$

Acid-Base Titrations Involving Multiple Acids or Bases

Acid–base titrations involving multiple acidic or basic components—like polyprotic acids—proceed in various stages. Each ionizable proton is neutralized separately, generating individual equivalence points on the titration curve. For a diprotic acid there are two such points, for a triprotic acid, up to three. Well, some may merge if dissociation constants are similar. Between these points, buffer regions form where the pH changes gradually, often aligning with pKa values at half‑equivalence stages.

Importance and Scope of Chemistry

We know that chemistry deals with the study of composition, structure and properties of matter and the changes which the matter undergoes under different conditions and the laws which govern these changes.

Chemistry deals with:

1.) Increase in the production of food through use of chemical fertilizers, insecticides, fungicides and pesticides.

2.) Contribution to better health and sanitation through the use of life saving drugs, e.g., cisplatin and taxol for cancer and AZT for AIDS and also through the use of analgesics, antibiotics, tranquilizers, antiseptics, disinfectants, insecticides and anaesthetics.

3.) Saving the environment by use of environment friendly chemicals.

4.) Increase in comfort and luxury by use of synthetic fibres, building materials, metals like iron, aluminium, copper, silver, gold etc. and articles of domestic use like soaps, detergents, paper, glass, plastics etc.

5.) Nuclear and atomic energy involving use of uranium and plutonium for nuclear reactors.

6.) Transport which involves use of petrol and diesel and other high quality fuels for aeroplanes etc.

Also Read:

• Mole Concept Basic
• Empirical And Molecular Formula
• Laws Of Chemical Combination For Elements And Compounds

Some Solved Examples

Example 1
Question: A solid mixture (10g) consisting of operator name MgCO₃ and Na₂CO₃ was heated until the mass of the residue was constant. If the loss in mass is 44%, find the amount of MgCO3 and Na₂CO₃ in the mixture respectively.

1) 8.4g, 1.6g

2) 1.6g, 8.4g

3) 5g, 5g

4) 8.8g, 1.2g

Solution

The reactions occur as follows:

$\mathrm{MgCO}_3 \xrightarrow{\Delta} \mathrm{MgO}+\mathrm{CO}_2$

$\mathrm{Na}_2 \mathrm{CO}_3 \xrightarrow{\Delta} x$

Mass is lost in the form of CO₂

Thus, the weight of CO₂ = 4.4g

Thus, moles of CO₂ = 0.1 = moles of MgCO₃

Therefore, mass of MgCO₃ in the mixture = 8.4g

Thus, mass of Na₂CO₃ in the mixture = 1.6g

Hence, the answer is the option (1).

Example 2
Question: A 20 g mixture of Na₂CO₃ and CaCO₃ is gently heated and produces 2.24 liters of CO2 at STP. What is the % weight of Na₂CO₃ in that sample?

1) 12.5%

2) 25%

3) 50%

4) 75%

Solution

We know that Na₂CO₃ does not decompose on heating. So CO₂ will be produced by only CaCO₃CaCO₃(s)→CaO(s) + CO₂(g)By reaction stoichiometry

Mole of CaCO₃ = mole of CO₂

Mole of CaCO₃ = 2.24 litre

A mole of CaCO₃ = 2.24/22.4 mole

A mole of CaCO₃ = 0.1 moles Now,

Weight of CaCO₃ = mole X molar mass of CaCO₃

Weight of CaCO₃ = 0.1 X 100 = 10g

wt. of Na₂CO₃ = 20g - wt. of CaCO₃

wt. of Na₂CO₃ = 20g - 10 = 10g

% wt. of Na₂CO₃ = (10/20)X100 % = 50%

Hence, the answer is the option (3).

Example 3
Question: 25 ml of a solution containing HCl and H₂SO₄ requires 25 ml of 0.5M caustic soda for complete neutralization. 50 ml of the same solution on precipitation with excess BaCl₂ gave 2.33 g of precipitate BaSO₄. What is the strength of HCl in the solution (in g/L)?

1)36.5

2) 3.65

3)7.3

4)73

Solution

Let the molarity of HCl and H₂SO₄ be x and y respectively.

Now, upon neutralization, we have:

25(x+2y) = 25 x 0.5

x + 2y = 0.5

Next, upon precipitation, we have:

50 x y = (2.33/233) x 1000 = 10

y = 0.2 and x = 0.1

Thus, the molarity of HCl = 0.1

It means 3.65 g/L of HCl is present in the stock solution.

Hence, the answer is the option (2).

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Conclusion

Basics of chemistry therefore form the basis by which one would grasp issues about matters and their interaction. The definition of matter, elements, compounds, and moles are among the basic things a student should know as a professional. It is the identification of several forms of mixtures and chemical reactions that bring out the true complexity of the chemical process. The above concepts have applications in real life, from cookery and health to offering exploration in environmental science and industry.