Fundamentals of Chemistry Short Notes
Fundamentals of Chemistry Solved Short & Long Questions (Sindh Text Book Board Jamshoro)
Section: B Short Questions
Q1: Differenciate between the Physical and Analytical Chemistry.
Ans: Physical chemistry and analytical chemistry are two distinct subfields of chemistry with different focuses and goals:
Physical Chemistry:
Physical chemistry is the branch of chemistry that deals with the study of the physical and chemical properties of matter and the changes it undergoes.
Analytical Chemistry:
Analytical chemistry focuses on the identification and quantification of chemical compounds and elements in various samples.
Q2: Write down the classification of the molecule.
Ans: Molecules can be classified based on the number of atoms of the same or different elements that are chemically bonded together. Here's a classification based on the number of atoms:
Monoatomic Molecules:
Monoatomic molecules consist of a single atom of a chemical element.
Examples include noble gases like helium (He) and neon (Ne).
Diatomic Molecules:
Diatomic molecules are composed of two atoms of the same or different elements chemically bonded together.
Examples include Oxygen (O2), Nitrogen (N2), and Hydrogen Chloride (HCl).
Triatomic Molecules:
Triatomic molecules consist of three atoms chemically bonded together.
Examples include Ozone (O3) and Carbon dioxide (CO2).
Polyatomic Molecules:
Polyatomic molecules contain more than three atoms bonded together.
Examples include water (H2O), ammonia (NH3), and methane (CH4).
These classifications are based on the number of atoms within a molecule, and molecules can vary greatly in size and complexity, with some containing hundreds or even thousands of atoms.
Q3: Identify the difference among the following.
(a) Atom and Ion
(b) Molecule and Molecular Ion
(c) Compound and Mixture
Ans:
(a) Atom and Ion:
An atom is the basic unit of matter and consists of a nucleus (containing protons and neutrons) and electrons orbiting around the nucleus.
An ion is a charged species formed when an atom gains or loses electrons. Ions can be positively charged (cations) if they lose electrons or negatively charged (anions) if they gain electrons.
(b) Molecule and Molecular Ion:
A molecule is a group of two or more atoms held together by chemical bonds. These atoms can be of the same or different elements.
A molecular ion is a molecule with a net electric charge, often expressed with a superscript and either a plus or minus sign. It results from the gain or loss of electrons, making it an ion.
(c) Compound and Mixture:
A compound is a substance composed of two or more different elements chemically bonded together in a fixed ratio. Compounds have distinct properties and can be represented by a chemical formula.
A mixture is a combination of two or more substances in which each retains its individual properties. Mixtures can be homogeneous (uniform composition) or heterogeneous (non-uniform composition), and their components are physically intermingled but not chemically bonded.
In summary, atoms and ions differ in their electric charge, molecules and molecular ions can be similar in composition but differ in charge, and compounds and mixtures differ in their chemical composition and how their components are combined.
Q4: Define the following terms.
(a) Gram Atomic Mass
(b) Gram Molecular Mass
(c) Gram Formula Mass
Ans:
(a) Gram Atomic Mass:
The gram atomic mass, also known as molar mass, is the mass of one mole of atoms of a chemical element expressed in grams per mole. It is numerically equal to the atomic mass of the element in atomic mass units (u).
For example, the gram atomic mass of carbon (C) is approximately 12 grams per mole.
(b) Gram Molecular Mass:
The gram molecular mass, also known as molar mass, is the mass of one mole of molecules of a chemical compound expressed in grams per mole. It is calculated by summing the atomic masses of all the atoms in a molecule.
For example, the gram molecular mass of water (H2O) is approximately 18 grams per mole.
(c) Gram Formula Mass:
The gram formula mass, also known as molar mass, is the mass of one mole of formula units of an ionic compound. It is calculated similarly to the gram molecular mass but is used for ionic compounds, which do not exist as discrete molecules.
The formula mass includes the masses of all ions in the chemical formula, taking into account the ratios specified in the formula.
All three terms (gram atomic mass, gram molecular mass, and gram formula mass) are synonymous and represent the mass of one mole of a substance, whether it consists of atoms, molecules, or ions.
Q5: Write down the Empirical and Molecular Formula of the following.
i. Sulphuric Acid
ii. Carbon Dioxide
iii. Glucose
iv. Benzene
Ans: The Empirical and Molecular Formula of the Sulphuric acid, Carbon dioxide, Glucose, and Benzene are given as under.
i. Sulphuric Acid:
Empirical Formula: H2SO4
Molecular Formula: H2SO4
ii. Carbon Dioxide:
Empirical Formula: CO2
Molecular Formula: CO2
iii. Glucose:
Empirical Formula: CH2O
Molecular Formula: C6H12O6
iv. Benzene:
Empirical Formula: CH
Molecular Formula: C6H6
Note:
The empirical formula represents the simplest whole-number ratio of the elements in a compound, while the molecular formula represents the actual number of each type of atom in a molecule of the compound. In the cases provided, the empirical and molecular formulas are the same for sulphuric acid and carbon dioxide. However, for glucose and benzene, the molecular formulas are multiples of the empirical formulas.
Q6: What is the Free Radical in Chemistry?
Ans: In chemistry, a free radical is a highly reactive, unstable molecular species with one or more unpaired electrons. These unpaired electrons make free radicals very reactive because they seek to pair up with other electrons, leading to chemical reactions.
Common examples of free radicals include hydroxyl radicals (•OH), superoxide radicals (•O2−), and nitric oxide (•NO). Understanding the chemistry of free radicals is essential in fields like organic chemistry, biochemistry, and environmental science.
Q7: Describe the relationship between Empirical and Molecular Formula. Explain with some examples.
Ans: The relationship between empirical and molecular formulas is based on the concept that the empirical formula represents the simplest whole-number ratio of the elements in a compound, while the molecular formula shows the actual number of each type of atom in a molecule of the compound.
Here are some examples:
Hydrogen Peroxide:
Empirical Formula: HO
Molecular Formula: H2O2
Here, the empirical formula shows the simplest ratio of hydrogen to oxygen, which is 1:1. The molecular formula, however, reveals that each molecule of hydrogen peroxide contains two hydrogen atoms and two oxygen atoms.
Glucose:
Empirical Formula: CH2O
Molecular Formula: C6H12O6
The empirical formula of glucose represents the simplest ratio of carbon, hydrogen, and oxygen atoms. However, the molecular formula discloses that a glucose molecule is composed of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
Q8: Explain why Hydrogen and Oxygen are called elements whereas, water is considered a compound?
Ans: Hydrogen and oxygen are called elements, while water is considered a compound because of their fundamental differences in chemical composition:
Hydrogen (H) and Oxygen (O) as Elements:
An element is a pure substance composed of only one type of atom. Both hydrogen and oxygen consist of only one kind of atom: hydrogen is made up of hydrogen atoms (H), and oxygen is composed of oxygen atoms (O).
Water (H2O) as a Compound:
A compound is a substance formed when two or more different elements chemically combine in fixed ratios. Water, with the chemical formula H2O, is composed of hydrogen and oxygen chemically bonded together.
Unlike elements, compounds can be separated into their constituent elements by chemical reactions. For example, water can be split into hydrogen and oxygen through a process like electrolysis.
Section: C Long/Detailed Questions
Q1: What do you mean by the Chemical Species? Explain in the context of Ion, Molecular Ion, and Free Radicals.
Ans: Chemical species refer to distinct entities or particles in chemistry that can be involved in chemical reactions and have specific properties. Here's an explanation in the context of ions, molecular ions, and free radicals:
Ion:
An ion is a chemical species that results from the gain or loss of electrons by an atom or molecule. It can be positively charged (cation) if it loses electrons or negatively charged (anion) if it gains electrons.
Example: A sodium ion (Na+) is a cation formed when a sodium atom loses one electron. A chloride ion (Cl-) is an anion formed when a chlorine atom gains an electron.
Molecular Ion:
A molecular ion is a specific type of ion that consists of a molecule with a net electric charge. Molecular ions can be formed by adding or removing electrons from a molecule without breaking its chemical bonds.
Example: The molecular ion in the compound water (H2O) is H2O+. It is formed by removing an electron from the water molecule.
Free Radical:
A free radical is a type of chemical species characterized by having one or more unpaired electrons in its outer electron shell. These unpaired electrons make free radicals highly reactive because they seek to pair up with other electrons through chemical reactions.
Example: The hydroxyl radical (•OH) is a free radical formed when a hydrogen peroxide molecule (H2O2) breaks down into two hydroxyl radicals. The unpaired electron in the hydroxyl radical makes it very reactive in various chemical reactions.
In a nutshell, chemical species encompass ions, molecular ions, and free radicals, each of which represents a distinct entity with a specific electrical charge or unpaired electrons, influencing their reactivity and behavior in chemical reactions.
Q2: Write down the applications of the Chemistry in daily life.
Ans: Chemistry plays a crucial role in various aspects of our daily life, and its applications are widespread.
Here are some common applications of chemistry in daily life:
Medicine and Healthcare:
- Drug development and pharmaceuticals.
- Diagnosis and treatment of diseases.
- Development of medical devices and materials.
Food and Nutrition:
- Food preservation, including canning, refrigeration, and additives.
- Nutritional analysis and labeling.
- Cooking and baking processes.
Cleaning and Hygiene:
- Development of soaps, detergents, and cleaning agents.
- Water purification and wastewater treatment.
- Personal care products like cosmetics and toiletries.
Energy Production:
- Fossil fuel combustion and energy generation.
- Alternative energy sources, including solar cells and batteries.
- Fuel efficiency and emissions reduction.
Environmental Protection:
- Environmental monitoring and pollution control.
- Hazardous waste management and remediation.
- Sustainable and green chemistry practices.
Materials and Manufacturing:
- Development of new materials, such as polymers and composites.
- Quality control and testing in manufacturing processes.
- Nanotechnology and advanced materials.
Agriculture and Food Production:
- Crop protection and pesticide development.
- Fertilizers and soil chemistry.
- Genetic modification of crops.
Home and Personal Life:
- Home improvement and maintenance, including paints and adhesives.
- Understanding product labels and safety information.
- Personal activities like gardening and food preparation.
Transportation and Communication:
- Fuel development for vehicles and aircraft.
- Development of communication devices and materials.
- Infrastructure and construction materials.
Education and Research:
- Chemistry as an academic field and for scientific research.
- Laboratory techniques and equipment.
- Development of educational materials and curricula.
These are just a few examples, and the applications of chemistry in daily life are extensive. Chemistry is fundamental to understanding the world around us and finding solutions to many of our everyday challenges and needs.
Q3: Explain in detail the Empirical and Molecular Formula.
Ans: Empirical and molecular formulas are ways of expressing the composition of chemical compounds. They provide information about the types and ratios of atoms within a compound. Here's a detailed explanation of both:
Empirical Formula
Definition:
The empirical formula represents the simplest whole-number ratio of the elements in a compound. It doesn't provide the actual number of atoms but gives you the relative proportions.
Example:
Let's consider glucose (C6H12O6). To find the empirical formula, you need to determine the simplest ratio of carbon (C), hydrogen (H), and oxygen (O).
In glucose, there are six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. To simplify to the empirical formula, you can divide all the subscripts by the greatest common factor, which is 6 in this case.
Original ratio: C6H12O6
Empirical formula: CH2O
Use:
The empirical formula is especially useful when you want to understand the basic composition of a compound in the simplest terms, without knowing the exact number of atoms in a molecule.
Molecular Formula
Definition:
The molecular formula represents the actual number of each type of atom in a molecule of the compound. It provides a detailed and precise description of the compound's composition.
Example:
Using the example of glucose (C6H12O6), the molecular formula tells us that each glucose molecule consists of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. The molecular formula is the same as the empirical formula in this case.
Use:
The molecular formula is important when you need to know the exact composition of a molecule. It's particularly valuable in organic chemistry, where molecules can be large and complex.
In conclusion, the empirical formula gives you the simplest whole-number ratio of elements in a compound, while the molecular formula provides the actual number of each type of atom in a molecule.
The molecular formula is a multiple of the empirical formula in some cases, depending on how the atoms are arranged within the molecule. Both formulas are essential tools in understanding and representing chemical compounds.
Q4: Explain the steps for balancing the equation.
Ans: Balancing a chemical equation is the process of ensuring that the number of atoms of each element on both sides of the equation (reactants and products) is the same.
It's a fundamental skill in chemistry to represent chemical reactions accurately. Here are the steps to balance a chemical equation:
1. Write the Unbalanced Equation:
Begin by writing down the chemical equation representing the reaction. Make sure you have correctly identified the reactants and products.
2. Count the Atoms:
Count the number of atoms of each element on both sides of the equation. Start with elements that appear only once on each side of the equation, and then move on to elements in multiple compounds.
3. Adjust the Coefficients:
To balance the equation, add coefficients (whole numbers) in front of the chemical formulas to make the number of atoms of each element equal on both sides. You can change coefficients but not subscripts.
4. Use the Lowest Common Multiple:
When balancing, try to use the lowest common multiple for coefficients. This ensures you have the simplest, most balanced equation.
5. Check and Recount:
After adjusting coefficients, re-count the number of atoms for each element on both sides of the equation. If the equation is balanced, the counts will be the same. If it's not balanced, continue adjusting coefficients.
6. Special Considerations:
Be aware of diatomic elements (like O2 and H2) and polyatomic ions. Treat them as single units when balancing.
7. Maintain Whole Numbers:
Make sure that all coefficients are whole numbers. If you end up with fractional coefficients, multiply the entire equation by a suitable factor to convert them into whole numbers while keeping the ratios the same.
8. Double-Check:
Carefully review the entire equation to ensure that it's balanced. Pay attention to elements that may be present in multiple compounds and make any necessary adjustments.
9. Record the Balanced Equation:
Once the equation is balanced, write down the coefficients as the final, balanced chemical equation.
10. Optional: Check for Conservation Laws:
Verify that the law of conservation of mass and the law of conservation of charge are satisfied.
This means that the total mass of reactants equals the total mass of products and the total charge (sum of charges) remains the same on both sides of the equation.
Balancing chemical equations may take some practice, but it's an essential skill in chemistry. It ensures that the stoichiometry (the ratios of reactants and products) is accurately represented in chemical reactions.
Q5: Name the branches of Chemistry and discuss any five of them.
Ans: Chemistry is a diverse and broad field, and it can be divided into several branches, each focusing on specific aspects of matter and its interactions.
Branches of Chemistry
Chemistry is a diverse field with many branches, and here are the names of some of the major branches of chemistry:
1. Organic Chemistry
2. Inorganic Chemistry
3. Physical Chemistry
4. Analytical Chemistry
5. Biochemistry
6. Environmental Chemistry
7. Medicinal Chemistry
8. Industrial Chemistry
9. Agricultural Chemistry
10. Food Chemistry
11. Polymer Chemistry
12. Nuclear Chemistry
13. Forensic Chemistry
14. Atmospheric Chemistry
15. Green Chemistry
Each of these branches has its own specialized focus and plays a crucial role in various industries and scientific research.
Here are five branches of chemistry, along with brief explanations of each:
1. Organic Chemistry:
Organic chemistry is the study of compounds primarily composed of carbon and hydrogen, often with other elements like oxygen, nitrogen, and halogens. It focuses on the structure, properties, reactions, and synthesis of organic compounds, including hydrocarbons and their derivatives.
Example: Investigating the synthesis of pharmaceuticals, the study of the structure of natural compounds like DNA, and understanding the properties of hydrocarbons in fossil fuels.
2. Inorganic Chemistry:
Inorganic chemistry deals with the study of inorganic compounds, which typically do not contain carbon-hydrogen (C-H) bonds. It covers a wide range of compounds, including metals, minerals, and organometallic compounds.
Example: Examining the properties and reactivity of metals and their compounds, understanding the behavior of minerals and inorganic materials, and studying coordination compounds used in catalysts.
3. Physical Chemistry:
Physical chemistry focuses on the principles of physical and chemical changes, emphasizing the laws of thermodynamics, quantum mechanics, and kinetics. It helps explain the behavior of matter at the molecular and atomic levels.
Example: Investigating reaction rates, understanding phase transitions, studying chemical equilibria, and applying thermodynamics to energy and chemical processes.
4. Analytical Chemistry:
Analytical chemistry involves the identification and quantification of chemical compounds and elements in various samples. It encompasses techniques for chemical analysis, including spectroscopy, chromatography, and mass spectrometry.
Example: Analyzing environmental samples for pollutants, testing the composition of pharmaceutical drugs, and ensuring food safety by detecting contaminants.
5. Biochemistry:
Biochemistry is the study of the chemical processes and substances that occur within living organisms. It explores the structure and function of biological macromolecules like proteins, nucleic acids, and lipids, as well as metabolic pathways and enzymatic reactions.
Example: Understanding the role of enzymes in cellular reactions, studying DNA replication and protein synthesis, and investigating metabolic pathways in metabolism and nutrition.
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