Chemistry Chapter on Balanced Equations

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Questions and Answers

What is a balanced chemical equation?

An equation where the number of molecules is equal on both sides

An equation that allows for the change of subscript numbers

An equation where reactants are present in larger quantities than products

An equation where the number of atoms for each element is equal on both sides (correct)

Which of the following steps is NOT part of balancing a chemical equation?

Change a word equation into a formula

Balancing all atoms simultaneously (correct)

Balancing atoms that appear in a single molecule first

Balancing oxygen and hydrogen last

What do coefficients in a chemical equation represent?

The pressure exerted during the reaction

The temperature at which the reaction occurs

The types of atoms in the reaction

The number of molecules involved in the reaction (correct)

What occurs during a chemical reaction?

Atoms are rearranged but not created or destroyed Signup and view all the answers

Which of these components is NOT part of a chemical reaction?

Reactant remainders Signup and view all the answers

What is the role of subscript numbers in a chemical formula?

They represent the number of atoms of each element Signup and view all the answers

In the cellular respiration reaction, how many carbon atoms are present in both reactants and products?

6 Signup and view all the answers

What are the main products formed during the reaction of glucose and oxygen gas?

Carbon dioxide and water Signup and view all the answers

What does the pH scale indicate about a solution with a pH of 3?

It is strongly acidic Signup and view all the answers

Which phase change involves a substance transitioning directly from a solid to a gas?

Sublimation Signup and view all the answers

Which of the following is true regarding the organization of the periodic table?

It is organized primarily by atomic number Signup and view all the answers

What is the primary role of buffers in the human body?

To maintain stable pH levels Signup and view all the answers

Identify the process that occurs when a gas loses energy to become a liquid.

Condensation Signup and view all the answers

What characteristic of metals can be predicted from their position on the periodic table?

They have multiple oxidation states Signup and view all the answers

What do all substances with a pH of 7 have in common?

They are neutral Signup and view all the answers

How can the number of valence electrons in an atom be determined for most elements?

By referencing the group number on the periodic table Signup and view all the answers

What effect does gaining electrons have on the ionic radius of an atom?

It increases the ionic radius. Signup and view all the answers

How does ionization energy change as you move from left to right across a period?

Ionization energy increases. Signup and view all the answers

Which factor does NOT influence the ionization energy of an atom?

The atomic mass of the element. Signup and view all the answers

What is the relationship between electronegativity and bond polarity?

Greater electronegativity difference leads to more polar bonds. Signup and view all the answers

What does nuclear shielding explain in relation to ionization energy?

It neutralizes the positive charge of the nucleus, decreasing ionization energy. Signup and view all the answers

Which trend is observed when moving down a group in the periodic table?

Atomic radius increases. Signup and view all the answers

What is the consequence of an atom becoming a cation?

The atomic radius decreases. Signup and view all the answers

What describes the trend in electronegativity on the periodic table?

It increases from bottom left to top right. Signup and view all the answers

What is the result of having identical electronegativity values between two atoms?

They form nonpolar bonds. Signup and view all the answers

Study Notes

Chemical Reactions and Equations

A balanced chemical equation reflects equal numbers of atoms for each element on both the reactant and product sides.
This concept adheres to the law of conservation of matter, which states matter cannot be created or destroyed.
Coefficients are used to balance equations, while subscripts should remain unchanged to retain the identity of chemicals.
Steps for balancing include converting word equations to formulas, balancing atoms systematically, and verifying equality of reactants and products.
Reactants are substances that undergo a change in a reaction, while products are the substances formed.

Phase Changes

Phase changes occur when a system experiences energy or pressure variations, leading to transitions among solid, liquid, and gas.
Key phase transitions include:
- Evaporation/Boiling: Liquid to gas at a specific temperature.
- Condensation: Gas to liquid as it loses energy.
- Sublimation: Solid to gas without passing through a liquid state.
- Deposition: Gas directly to solid.
- Freezing: Liquid to solid through energy loss.
- Melting: Solid to liquid through energy gain.
The critical point defines the temperature and pressure at which liquid and vapor become indistinguishable.

pH Scale and Acids/Bases

The pH scale ranges from 0 (acidic) to 14 (basic), with 7 being neutral.
Acids release hydrogen ions (H+) in solution, while bases release hydroxide ions (OH-).
Solutions with decreasing pH have increasing concentrations of hydrogen ions.
Buffers help maintain pH stability in biological systems, essential for enzyme function.
Common acids and bases include lemon juice (acid) and soap (base).

Periodic Table and Trends

The periodic table organizes elements by increasing atomic number or the number of protons.
Early classifications included Johann Dobereiner's Law of Triads and John Newlands' Law of Octaves.
Mendeleev refined the table, while Moseley’s insights led to the modern arrangement based on atomic number.
Elements are categorized as metals, nonmetals, or metalloids, with various trends indicating properties such as atomic radius and electronegativity.

Valence Electrons and Electron Configuration

Valence electrons determine an atom's chemical properties and reactivity.
The group number in the periodic table typically indicates the number of valence electrons, except for transition metals.
Electron configurations describe electron arrangement, with s, p, d, and f orbitals having varying capacities (e.g., s: 2, p: 6, d: 10, f: 14).
Oxygen, with six valence electrons, has an electron configuration of 1s² 2s² 2p⁴.

Ionic Radius and Ionization Energy

Ionic radius varies based on electron gain or loss; anions (gained electrons) are larger, while cations (lost electrons) are smaller than their parent atoms.
Atomic and ionic radii trends increase down a group and decrease across a period.
Ionization energy, the energy required to remove the outermost electron, increases across a period and decreases down a group due to atomic structure.

Electronegativity and Covalent Bonding

Electronegativity measures an atom's ability to attract electrons, impacting bond polarity.
Differences in electronegativity (ΔEN) are crucial for determining if bonds are polar (unequal sharing) or nonpolar (equal sharing).
Elements in biological systems typically have electronegativities greater than 2.00, forming essential covalent compounds.

Physical Properties of Substances

Physical properties can be observed without altering the substance's composition, including mass, density, melting/boiling points, and solubility.
Mass quantifies matter, while density measures mass per volume, indicating how compact a substance is.
Melting and boiling points signify state changes, with solubility reflecting a substance's ability to dissolve in solvents.

Role of Carbon in Life

Carbon, essential for all known life forms, is a component of various compounds and molecules.
Carbon-based molecules include nucleic acids, carbohydrates, proteins, and lipids, crucial for biological functions and processes like respiration and photosynthesis.

Characteristics of Living Systems

Living organisms exhibit organized structures, growth, energy utilization, environmental responses, adaptability, homeostasis maintenance, and reproduction.
All life forms on Earth share a carbon-based molecular structure, underscoring the fundamental role of carbon in biology.

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Description

Explore the concept of balanced chemical equations, where the number of atoms in reactants equals those in products. This fundamental principle upholds the law of conservation of matter. Learn how to use coefficients to balance equations without altering chemical identities.