Notes, summaries, assignments, exams, and problems for Chemistry

Unit 4: Atoms and Their Models

UNIT 4

Atoms are the basis of all the structures and organisms in the universe.

2. Models of the Atom

A model is a representation of a system in the real world. Models help us to understand systems and their properties.

2.1 Dalton's Model of the Atom

John Dalton proposed that all matter is composed of very small things which he called atoms.

2.2 Thomson's Model of the Atom

In this model, the atom is made up of negative electrons that float in a soup of positive charge, much like plums in a pudding or raisins in a fruit cake.

2.3 Rutherford's Model of the Atom

His new model described the atom as a tiny, dense, positively charged core called a nucleus surrounded by lighter, negatively charged electrons.

2.4 Bohr's Model of

• Lexeme: The abstract vocabulary item listed in the lexicon with a common core of meaning.
• Word-forms: Physical realizations of the lexeme.
• Paradigm: The list of word-forms that belong to a word.
• Morpheme: The smallest unit of analysis with semantic content or grammatical function that words are made up of.
• Morph: The physical realization of the morpheme. Morphs are made up of one or more morphemes.
• Syncretism: Identical word-forms that belong to the same lexeme but are different grammatical words.
• Root: The basic form that remains when you get rid of all the affixes.
• Stem: A term that we only use in inflectional morphology; it is the form to which you attach an inflectional affix (only suffixes in English).
• Base: Anything; any root and any stem are

Intermolecular Forces (IMFs)

IMFs include: Covalent, Hydrogen, Metallic, Dipole, London, and Ion interactions.

Solution Chemistry Formulas

• pH (Acidic Solutions): $\text{pH} = -\log[\text{H}^+] = -\log N = \text{p}H_A = \sqrt{K_a M}$ (where $K_a = x^2/M$ and $-\log x = \text{p}OH$ is incorrect in this context, use $\text{pH} = 14 - \text{pOH}$)
• pOH (Basic Solutions): $\text{pOH} = -\log[\text{OH}^-] = -\log N$. For weak bases (WB): $K_b = x^2/M$ and $-\log x = \text{pOH}$, leading to $\text{pH} = 14 - \text{pOH}$.

Strong Acids

Common strong acids include: $\text{HNO}_3$, $\text{H}_2\text{SO}_4$, $\text{HBr}$, $\text{HI}$, $\text{HClO}_4$, and $\text{HClO}_3$.

Lewis Acid

A compound or ionic species that can accept an electron pair from a donor compound.... Continue reading "Chemical Bonding and Solution Chemistry Concepts" »

1.Who propossed the theory of One-dimensional consolidation? Karl Terzaghi

2.What types of permeameters exist in Lab tests? Constant head permeameter and Failing head permeameter

3.What is the name of the equation that Governs the 2D underground flow? Laplace’s Equation.

4.Name of the method of draw flow nets That uses iterative calculations. Finite Differences

5.What are the units of the compression Index Cc? Adimensional, NOT UNITS

6.Describe boiling in soils. Boiling of soils occurs when there is an Upward flow and the seepage force is greater that the submerged weight of the Soil.

7.What are the assumptions in laplace’s Equation. Darcy’s law applies, Water and Solids are uncompressible

8.When in it better to use failing head permeameter?

Q#9.1: How order of reaction is experimentally determined.

Ans. Order of reaction is determined by the following two methods.

1. From Rate Law.

   In this method, the rate of reaction is measured using chemical and physical methods (volumetric, gravimetric, spectrophotometer, pH-meter, conductometric methods). The dependence of the rate of reaction on the concentration of reactants tells us about the order of reaction. For example, a reaction in which the rate of reaction doubles when the concentration of reactants is doubled will be of first order. If the rate increases four times by doubling the concentration, the reaction will be of second order.

2. Ostwald’s Isolation Or Large Excess Method.

   This method is used to determine the order of complicated

Photoelectric Effect Explained

The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner are called photoelectrons.

Specifically, when light shines on a metal, electrons can be ejected from its surface. This phenomenon, where light waves hitting a metal surface cause electrons to be ejected, is a fundamental aspect of the photoelectric effect.

Chemical Bonds: Types and Strengths

Understanding Chemical Bonds: Strongest to Weakest

Chemical bonds are the forces that hold atoms together to form molecules. Here are three types, generally ordered from strongest to weakest:

1. Ionic Bonding

   Ionic bonding involves a transfer of an electron, where one atom gains an electron while

Questions

Answers

Why do you use distilled water in your experiments?

Because distilled water has all its impurities removed through distillation.

What is the formula for converting oC to Fahrenheit( F)?

(oC x 1.8) + 32

Formula for converting oF into Celsius

 (oF - 32)  1.8

Formula for converting oC to Kelvin(K)

K = oC + 273.15

Name all the volumetric apparatus used in the lab

Beaker, measuring cylinder, Burette, Pipet, and volumetric flask. (See the attachment)

A student got the following results in his experiment: 14.9g, 14.19g, 14.88g, 14.92g, but the actual weight is 20.90g. How accurate are the student results. And how precise are the results.

The student results are not accurate but precise. Has the precision of  0.05g

Sketch 2 pieces of glassware: