Monday 17 October 2011

Significant Figures and Scientific Notation Test

Question 1

How many significant figures are in the following values?
a. 4.02 x 10-9
b. 0.008320
c. 6 x 105
d. 100.0

Question 2

How many significant figures are in the following values?
a. 1200.0
b. 8.00
c. 22.76 x 10-3
d. 731.2204

Question 3

Which value has more significant figures?
2.63 x 10-6 or 0.0000026

Question 4

Express 4,610,000 in scientific notation.
a. with 1 significant figure
b. with 2 significant figures
c. with 3 significant figures
d. with 5 significant figures

Question 5

Express 0.0003711 in scientific notation.
a. with 1 significant figure
b. with 2 significant figures
c. with 3 significant figures
d. with 4 significant figures

Question 6

Perform the calculation with the correct number of significant digits.
22.81 + 2.2457

Question 7

Perform the calculation with the correct number of significant digits.
815.991 x 324.6

Question 8

Perform the calculation with the correct number of significant digits.
3.2215 + 1.67 + 2.3

Question 9

Perform the calculation with the correct number of significant digits.
8.442 - 8.429

Question 10

Perform the calculation with the correct number of significant digits.
27/3.45

Answers

1. a. 3   b. 4   c. 1   d. 4
2. a. 5   b. 3   c. 4   d. 7
3. 2.63 x 10-6
4. a. 5 x 106   b. 4.5 x 106   c. 4.61 x 106   d. 4.6100 x 106
5. a. 4 x 10-4   b. 3.7 x 10-4   c. 3.71 x 10-4   d. 3.711 x 10-4
6. 25.06
7. 2.649 x 105
8. 7.2
9. 0.013
10. 7.8
 

Wednesday 5 October 2011

Chemistry Question of the Day

At standard temperature and pressure, all of the following compounds exist in gas state EXCEPT

  1. HCl
  2. HBr
  3. NH3
  4. BH3
  5. LiH

Monday 19 September 2011

Format of GRE Chemistry Test

  • The test consists of about 130 multiple-choice questions.
  • A periodic table is printed in the test booklet as well as a table of information presenting various physical constants and a few conversion factors among SI units. Whenever necessary, additional values of physical constants are printed with the text of the question.
  • Test questions are constructed to simplify mathematical manipulations. As a result, neither calculators nor tables of logarithms are needed. If the solution to a problem requires the use of logarithms, the necessary values are included with the question.
  • The content of the test emphasizes the four fields into which chemistry has been traditionally divided and some interrelationships among the fields. Because of these interrelationships, individual questions may test more than one field of chemistry.
  • Some examinees may associate a particular question with one field, whereas other examinees may have encountered the same material in a different field. For example, the knowledge necessary to answer some questions classified as testing organic chemistry may well have been acquired in analytical chemistry courses by some examinees.Consequently, the emphases of the four fields indicated in the following outline of material covered by the test should not be considered definitive.

I. ANALYTICAL CHEMISTRY - 15%

A. Data Acquisition and Use of Statistics - Errors, statistical considerations
B. Solutions and Standardization - Concentration terms, and primary standards
C. Homogeneous Equilibria - Acid-base, oxidation-reduction, complexometry
D. Heterogeneous Equilibria - Gravimetric analysis, solubility, precipitation titrations, chemical separations
E. Instrumental Methods - Electrochemical methods, spectroscopic methods, chromatographic methods, thermal methods, calibration of instruments
F. Environmental Applications
G. Radiochemical Methods - Detectors, applications

II. INORGANIC CHEMISTRY - 25%

A. General Chemistry - Periodic trends, oxidation states, nuclear chemistry
B. Ionic Substances - Lattice geometries, lattice energies, ionic radii and radius/ratio effects
C. Covalent Molecular Substances - Lewis diagrams, molecular point groups, VSEPR concept, valence bond description and hybridization, molecular orbital description, bond energies, covalent and van der Waals radii of the elements, intermolecular forces
D. Metals and Semiconductors - Structure, band theory, physical and chemical consequences of band theory
E. Concepts of Acids and Bases - Brønsted-Lowry approaches, Lewis theory, solvent system approaches
F. Chemistry of the Main Group Elements - Electronic structures, occurrences and recovery, physical and chemical properties of the elements and their compounds
G. Chemistry of the Transition Elements - Electronic structures, occurrences and recovery, physical and chemical properties of the elements and their compounds, coordination chemistry
H. Special Topics - Organometallic chemistry, catalysis, bioinorganic chemistry, applied solid-state chemistry, environmental chemistry

III. ORGANIC CHEMISTRY - 30%

A. Structure, Bonding, and Nomenclature - Lewis structures, orbital hybridization, configuration and stereochemical notation, conformational analysis, systematic IUPAC nomenclature, spectroscopy (IR and 1H and 13C NMR)
B. Functional Groups - Preparation, reactions, and interconversions of alkanes, alkenes, alkynes, dienes, alkyl halides, alcohols, ethers, epoxides, sulfides, thiols, aromatic compounds, aldehydes, ketones, carboxylic acids and their derivatives, amines
C. Reaction Mechanisms - Nucleophilic displacements and addition, nucleophilic aromatic substitution, electrophilic additions, electrophilic aromatic substitutions, eliminations, Diels-Alder and other cycloadditions
D. Reactive Intermediates - Chemistry and nature of carbocations, carbanions, free radicals, carbenes, benzynes, enols
E. Organometallics - Preparation and reactions of Grignard and organolithium reagents, lithium organocuprates, and other modern main group and transition metal reagents and catalysts
F. Special Topics - Resonance, molecular orbital theory, catalysis, acid-base theory, carbon acidity, aromaticity, antiaromaticity, macromolecules, lipids, amino acids, peptides, carbohydrates, nucleic acids, terpenes, asymmetric synthesis, orbital symmetry, polymers

IV. PHYSICAL CHEMISTRY - 30%

A. Thermodynamics - First, second, and third laws, thermochemistry, ideal and real gases and solutions, Gibbs and Helmholtz energy, chemical potential, chemical equilibria, phase equilibria, colligative properties, statistical thermodynamics
B. Quantum Chemistry and Applications to Spectroscopy - Classical experiments, principles of quantum mechanics, atomic and molecular structure, molecular spectroscopy
C. Dynamics - Experimental and theoretical chemical kinetics, solution and liquid dynamics, photochemistry

Chemistry Question of the Day

A hydrocarbon is burned in oxygen and the ratio of moles of carbon dioxides to the moles of water obtained is 2:1. Find the hydrocarbon if it has 2 main resonance structures.

  1. CH4
  2. C2H4
  3. C2H2
  4. C6H6
  5. None of the above.

Chemistry Question of the Day



PbF2(s), which is slightly soluble in water, is dissolved in water to form a saturated solution in equilibrium with solid PbF2. Which of the following will cause additional PbF2(s) to dissolve?


  1. Adding HNO3
  2. Adding Pb(NO3)2
  3. Adding a seed crystal
  4. Adding solid PbF2
  5. Evaporating some of the water to decrease the volume of solution