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Chemical Analysis of Salts: Anions and Cations

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Preliminary Test

Color of the Salt

Colourless

Absence of Cu 2+, Fe 2+, etc

Odour of the Salt

Ammoniacal smell

Vinegar smell

NH4

Acetate ion

Solubility

In water with no precipitate with Na2CO3

In dil HCl, soluble

NH4

No Group 1 cations

Salt is heated in a dry test tube

Colorless gas turns milky

Reddish brown fumes

Smell of ammonia

Pleasant smell

Carbonate

Nitrate ion

NH4

Acetate ion

Flame Test

Pale green

Brick red

Ba

Ca

Ash Test

Blue ash

Al


Systematic Analysis for Anions

Dil HCl is added to a little of the saltBrisk effervescence of a colorless gasCO3
Salt is rubbed with dil H2SO4 in a watch glassVinegar smellAcetate
Salt is heated with conc H2SO4Colorless pungent smelling gas is evolved and dense white fumes are produced when a glass rod dipped in NH4OH is shown near the mouth
... Continue reading "Chemical Analysis of Salts: Anions and Cations" »

Chemical and Biological Processes: Reactions, Compounds, and Cell Division

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Chemistry

What is a Chemical Change?

A chemical change is a reaction that causes new substances with new properties to form.

Evidence of a Chemical Change:

  • Gas bubbles
  • Light/Heat
  • Colour change (must be combined with another chemical evidence)
  • Precipitate forms

Physical Properties

Examples of physical properties include:

  • Melting point
  • Boiling point
  • Atomic mass
  • Colour
  • Malleability
  • Conductivity
  • Lustre

Key Terms:

  • a) Valence electron: electron in the outermost shell/orbit
  • b) Stable octet: full valence shell (usually 8)
  • c) Cation: positively charged ion (loses electron)
  • d) Anion: negatively charged ion (gains electron)

Chemical Formulas:

  • Aluminum chloride: AlCl3
  • Lead (IV) oxide: PbO2
  • Copper (II) nitrate: Cu(NO3)2
  • Beryllium carbonate: BeCO3
  • Sodium phosphide: Na3P
  • Barium hydroxide:
... Continue reading "Chemical and Biological Processes: Reactions, Compounds, and Cell Division" »

Fractional Distillation and Cracking Polymers: Separating Crude Oil

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To separate crude oil into its fractions, we use fractional distillation. This process occurs in an oil refinery. The crude oil is heated to about 350 degrees Celsius in a column that gets cooler higher up. Each fraction will evaporate and rise up the column until it reaches a part that is cool enough to condense it. The liquid goes into its respective tube and is separated from the rest of the crude oil. The smallest alkanes, which have a lower boiling point, will rise to the top. The largest fraction, bitumen, never evaporates and falls as a liquid to the bottom.

Cracking

Crude oil contains a mix of alkanes. Shorter alkanes are the most useful as fuels. We can obtain more shorter alkanes by breaking down the larger ones. This process is called... Continue reading "Fractional Distillation and Cracking Polymers: Separating Crude Oil" »

Understanding Dental Materials: Properties and Clinical Significance

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Chemical Bonding in Dental Materials

Primary Bonds

Factors Influencing Material Properties:

  1. Type of bond between atoms and molecules
  2. Inter-atomic distance
  3. Atomic packing

Matter: Any substance that has mass and occupies space.

Atom: The fundamental unit of matter, consisting of a central nucleus (protons and neutrons) surrounded by electrons.

Types of Primary Bonds:
  • Ionic Bond: Attraction between positive and negative ions. Characteristics: Strong, heat resistant, insulator, insoluble in organic solvents, basic bond in ceramics.
  • Covalent Bond: Sharing of electrons between two atoms. Characteristics: Strong, insulator, water insoluble, basic bond in polymers.
  • Metallic Bond: Attraction between positive atomic cores and free electrons. Characteristics: High
... Continue reading "Understanding Dental Materials: Properties and Clinical Significance" »

Essential Principles of Matter: States, Properties, and Laws

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Basic Definitions of Matter

  • Mass: The amount of matter an object has.
  • Volume: The amount of space a substance occupies.
  • Density: The relation of the amount of mass in a given volume.
  • Matter: Anything that has mass and volume.
  • Inertia: The tendency of an object to resist a change in motion.
  • Weight: The action of gravitational force on an object.

Units of Measurement

  • Newtons (N): A unit of force.
  • 1 N = 100 g
  • 1 kg = 1000 g

Properties of Matter

Chemical Properties

  • A material's property that becomes evident during or after a chemical reaction.
  • Examples: Flammability, reaction with O₂ (oxygen).

Physical Properties

  • Observed or measured without changing the composition of matter.
  • Examples: State, density, solubility, malleability, shape.

Changes in Matter

Chemical

... Continue reading "Essential Principles of Matter: States, Properties, and Laws" »

Crystalline Solids: Bonding Types and Physical Properties

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Classification of Crystalline Solids

In crystalline solids, the atoms, ions, or molecules are held together by various types of cohesive forces, which may be chemical bonds or intermolecular forces. Based on the nature of bonding between their constituent particles, crystalline solids are classified into distinct types.

Ionic Crystals

Ionic crystals are formed by the interaction of positive and negative ions. These ions are held together by strong electrostatic forces of attraction, also known as ionic bonds. Examples include NaCl, KNO3, Na2CO3, and K2Cr2O7.

Properties of Ionic Crystals

  • They occur in the solid state at room temperature.
  • They have a distinct geometrical shape due to the close packing of cations and anions.
  • They are very hard.
  • They are
... Continue reading "Crystalline Solids: Bonding Types and Physical Properties" »

Fundamental Laws of Chemistry and Physics Explained

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Essential Laws and Principles in Science

Avogadro's Law

Equal volumes of gases under identical temperature and pressure conditions will contain equal numbers of particles (atoms, ions, molecules, electrons, etc.).

Boyle's Law

At constant temperature, the volume of a confined gas is inversely proportional to the pressure to which it is subjected.

PV = k

Charles' Law

At constant pressure, the volume of a confined gas is directly proportional to the absolute temperature.

V = kT

Combining Volumes

Refer to Gay-Lussac's Law.

Conservation of Energy

Energy can be neither created nor destroyed; the energy of the universe is constant. This is the First Law of Thermodynamics.

Conservation of Mass

Also known as Conservation of Matter. Matter can be neither created nor... Continue reading "Fundamental Laws of Chemistry and Physics Explained" »

Essential Chemistry Formulas and Concepts

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Temperature Conversions

  • Celsius to Fahrenheit: F = (9/5) * C + 32
  • Celsius to Kelvin: K = C + 273

Atomic Structure

  • Atomic Mass: Protons + Neutrons (upper left symbol)
  • Atomic Number: Protons (bottom left symbol)

Quantum Mechanics

  • Planck's Constant (h): 6.6260755 x 10-34 J*s
  • Energy of a Photon: E = hv or E = hc / wavelength

Electronic Transitions

  • Absorption: When energy is absorbed by an atom, an electron is excited to a higher energy level or orbital.
  • Emission: When an electron relaxes from a higher energy orbital to a lower one, it emits a photon.

Filling Orbitals

s = 2, p = 6, d = 10, f = 14

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f

Periodic Trends

  • Atomic Radius: Increases down a group and decreases across a row.
  • Ionization Energy: Amount of energy
... Continue reading "Essential Chemistry Formulas and Concepts" »

Coh3 chemical name

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in the RUTHERFORDS atomic model, the electrons are orbiting around the nucleous. In the nucleus are the neutrons and protons. BOHRS atomic model, the electrons move in stable orbits around the nucleus. Each orbit present a different number of electrons. How do we identify isotopes? By the name of the chemical element followed by its mass number. The elements in the periodic table are grouped: increasing atomic number(periods), similarity in physical and chemical elements(columns). Crystals are a gorup of atoms ordered ina geometric structure.

Electrochemistry, Corrosion, and Acid-Base Chemistry

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Galvanic Reaction in the Mouth

Biting on aluminum foil can be painful and is usually noticed if you have metal in your mouth from dental work (e.g., fillings, crowns). Basically, when you bite on foil, you set up a battery in your mouth, and the electrical current stimulates nerve endings in your tooth. Here is what happens:

  • Pressure from biting brings two dissimilar metals (aluminum foil, mercury in fillings, or gold in crowns) in contact in a moist, salty environment (saliva).
  • The two metals have an **electrochemical potential difference** or voltage across them.
  • Electrons flow from the foil into the tooth (i.e., **electrical current**).
  • The current gets conducted into the tooth's root, usually by the filling or crown.
  • The current sets off a nerve
... Continue reading "Electrochemistry, Corrosion, and Acid-Base Chemistry" »