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

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Key Factors Influencing Chemical Reaction Rates

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Q#9.2: Explain factors affecting rate of reaction.

Ans.The following factors strongly influence the rate of a reaction

1.Nature Of Reactants. The rate of reaction between polar or ionic

molecule is very fast. While the rearrangement reactions are slower than ionic reactions. Similarly oxidation reduction reactions are also slower than ionic. Some metals like sodium reacts vigorously with oxygen at room temp while magnesium needs flame to react with oxygen.

2.Effect Of Concentration Of Reactants.

By increasing the amount of reactants, the rate of reaction also increases. Consider a reaction which is composed of a gaseous mixture or concentrated solution, contains many active particles per unit volume. Therefore the rate of such reactions is faster... Continue reading "Key Factors Influencing Chemical Reaction Rates" »

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Organic Compounds, Aldehydes, Ketones, Moles of Atoms, Chemical Equations

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Give the general formula and class of organic compounds for each of the following;

a) CH3-OH  methanol

b) CH3-O- CH3  either


How are aldehydes and ketones alike? How are they different?

Aldehydes and ketones are much alike in many of their reactions, owing to the presence of the carbonyl functional group in both


How many moles of atoms are there in each of the following?

a. 40.1 g Ca  1.00 mol Ca

b. 11.5 g Na  0.500 mol Na

c. 5.87 g Ni  0.100 mol Ni

d. 150 g S  4.68 mol S

e. 2.65 g Fe  0.0475 mol Fe

f. 0.007 50 g Ag  6.5 x 10^-5 mol Ag


1. What is the mass in grams of 2.25 mol of the element iron, Fe?

2.25 mol Fe x (55.9g Fe/ 1 mol Fe)= 126g Fe


2. What is the mass in grams of 0.375 mol of the element potassium, K?

0.375 mol K x (39.1g K/ 1

... Continue reading "Organic Compounds, Aldehydes, Ketones, Moles of Atoms, Chemical Equations" »
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Coh3 chemical name

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Limiting Reagents

Sometimes when reactions occur between two or more substances, one reactant runs out before the other. That is called the "limiting reagent". Often, it is necessary to identify the limiting reagent in a problem. 
Example: A chemist only has 6.0 grams of C2H2 and an unlimited supply of oxygen and he desires to produce as much CO2 as possible. If she uses the equation below, how much oxygen should she add to the reaction?

2C2H2(g) + 5O2(g) ---> 4CO2(g) + 2 H2O(l)

To solve this problem, it is necessary to determine how much oxygen should be added if all of the reactants were used up (this is the way to produce the maximum amount of CO2). 
First, we calculate the number of moles of C2H2 in 6.0 g of C2H2. To be able to calculate

... Continue reading "Coh3 chemical name" »

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Fundamental Physics: Sound, Radioactivity, Planets & Gravity

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Sound Questions from Exam #2

How does the density of the medium affect the speed of sound? The density of a medium is the second factor that affects the speed of sound; the greater the density, the faster the sound.

  • b) Which is the softest sound a human can hear? 20 Hz… 0 dB
  • c) What is an example of a sound which will cause immediate hearing loss? Jet engine. dB range for this sound: 120 dB
  • d) Two sounds are emitted at the same time: Sound A: 10 meters through air, Sound B: 10 meters through water: which travels faster? Sound B
  • e) In the dB or decibel scale, sound pressure is compared to: The softest a human can hear.

Solar System Planet Order

Solar system in order distance of planets from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus,

... Continue reading "Fundamental Physics: Sound, Radioactivity, Planets & Gravity" »

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Essential Physics & Chemistry Concepts

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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

... Continue reading "Essential Physics & Chemistry Concepts" »
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Chemistry Lab Questions and Answers

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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) 7TVxAAAAGUlEQVQYV2NgwAZYFaCiyYKCIlAmXAxV  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 7TVxAAAAH0lEQVQYV2NgQAOsBkABOJEkKCiCxIVI  0.05g

Sketch 2 pieces of glassware:

... Continue reading "Chemistry Lab Questions and Answers" »
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Key Concepts in Thermodynamics and States of Matter

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Kinetic Energy and the Nature of Matter

  • Kinetic Energy: The energy an object possesses due to its motion.
  • Kinetic Theory: States that all matter is composed of tiny particles in constant motion.

Pressure and Its Measurement

  • Gas Pressure: Results from the force exerted by a gas per unit surface area of an object.
  • Vacuum: An empty space devoid of particles and pressure.
  • Atmospheric Pressure: Arises from the collisions of atoms and molecules in the air with objects.
  • Barometer: A device used to measure atmospheric pressure.
  • Pascal (Pa): The SI unit of pressure.
  • Standard Atmosphere (atm): The pressure required to support 760 mm of mercury in a mercury barometer at 25ºC.

Phase Transitions and States of Matter

  • Vaporization: The conversion of a liquid to a gas
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Core Chemistry Concepts: Moles, Isotopes, Concentration & Yield

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Conservation of Mass

Conservation of mass: No atoms are lost or created during a chemical reaction. The mass of reactants equals the mass of products. Any observed change in mass typically involves a gas being produced or lost as a result of the reaction.

Isotopes and Relative Formula Mass (RFM)

Isotopes and RFM:

RAM — Relative atomic mass. RFM or Mr — relative formula mass; the sum of all RAMs in a formula.

Percentage abundance calculation (for an isotope mixture):

% abundance = (RAM × number of atoms of that element / RFM of the compound) × 100.

An isotope is an atom of an element that has the same number of protons and electrons but a different number of neutrons, so it has a different mass number. Isotopes of the same element react in the

... Continue reading "Core Chemistry Concepts: Moles, Isotopes, Concentration & Yield" »

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Investment Portfolio Optimization: Sensitivity Analysis

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Impact of Minimum CD & Treasury Bond Investment

Question: If the amount invested in CDs and treasury bonds is at least $5,000 plus 1.2 times the amount invested in municipal bonds and growth stocks, what is the new optimal solution and Optimal Feasible Value (OFV)?

Answer: Since the allowable increase is greater than $5,000 and this is a binding constraint, you must re-solve the problem to obtain the new optimal solution. The new OFV can be estimated using the shadow price: New OFV ≈ Old OFV + 5000 * (-0.0295).

Adding a GIC Investment Alternative

Question: If there is another investment alternative in Guaranteed Investment Certificates (GICs) with a Return on Investment (ROI) of 10%, what is the new optimal solution and OFV?

Answer: Introducing... Continue reading "Investment Portfolio Optimization: Sensitivity Analysis" »

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Essential Science Knowledge: Biology & Chemistry

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Fundamental Science Concepts

1. Key Definitions in Chemistry and Physics

Match the word with its definition:

  • Chemical Reaction: A process in which one or more substances (the reactants) are converted to one or more different substances (the products).
  • Enzyme: Any of various proteins, originating from living cells, capable of producing chemical changes in organic substances.
  • Catalyst: A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
  • Viscosity: The state of being thick, sticky, and semifluid in consistency, due to internal friction.

2. Common Chemical Formulas

Write the chemical formula for the following substances:

  • Water: H2O
  • Oxygen: O2
  • Hydrogen Peroxide: H2O2

3. Main Shapes of Bacteria

Identify... Continue reading "Essential Science Knowledge: Biology & Chemistry" »

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